From 94bac81314ae8133a7c364ae59bc8ff5b6cef551 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Thu, 23 Apr 2026 17:32:40 +0100
Subject: [PATCH 01/23] Add and use XYLayout.map_point_to_screen()

---
 addons/tau-plot/plot/xy/bar/bar_hit_tester.gd |  4 +--
 .../plot/xy/scatter/scatter_renderer.gd       | 34 +++++--------------
 addons/tau-plot/plot/xy/xy_layout.gd          | 26 ++++++++++++++
 3 files changed, 36 insertions(+), 28 deletions(-)

diff --git a/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd b/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd
index d6799cb..e7d136a 100644
--- a/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd
@@ -80,14 +80,12 @@ class BarHitTester extends OverlayHitTester:
 		if _layout.domain.config.x_axis.type == TauAxisConfig.Type.CATEGORICAL:
 			return {}
 
-		# TODO: drop x_is_horizontal once XYLayout exposes a logical-x projector.
-		var x_is_horizontal: bool = _layout._x_is_horizontal
 		var best_px := INF
 		var best_val: float = 0.0
 		var found := false
 
 		for record: BarHitRecord in _bar_renderer.get_hit_records():
-			var anchor_along_x: float = record.anchor.x if x_is_horizontal else record.anchor.y
+			var anchor_along_x: float = _layout.map_screen_to_point(record.anchor).x
 			if absf(p_along_x_px - anchor_along_x) < absf(p_along_x_px - best_px):
 				best_px = anchor_along_x
 				best_val = record.x_value
diff --git a/addons/tau-plot/plot/xy/scatter/scatter_renderer.gd b/addons/tau-plot/plot/xy/scatter/scatter_renderer.gd
index 815e73d..188eab2 100644
--- a/addons/tau-plot/plot/xy/scatter/scatter_renderer.gd
+++ b/addons/tau-plot/plot/xy/scatter/scatter_renderer.gd
@@ -695,18 +695,11 @@ class ScatterRenderer extends Control:
 		# exactly on the pane boundary due to floating-point rounding in layout
 		# mapping. This is purely cosmetic and does not affect layout or ticks.
 		const TOLERANCE_PX := 0.5
-		var screen_x: float
-		var screen_y: float
-		if _layout._x_is_horizontal:
-			screen_x = p_x
-			screen_y = p_y
-		else:
-			screen_x = p_y
-			screen_y = p_x
-		return (screen_x >= p_pane_rect.position.x - TOLERANCE_PX and
-				screen_x <= p_pane_rect.position.x + p_pane_rect.size.x + TOLERANCE_PX and
-				screen_y >= p_pane_rect.position.y - TOLERANCE_PX and
-				screen_y <= p_pane_rect.position.y + p_pane_rect.size.y + TOLERANCE_PX)
+		var screen := _layout.map_point_to_screen(p_x, p_y)
+		return (screen.x >= p_pane_rect.position.x - TOLERANCE_PX and
+				screen.x <= p_pane_rect.position.x + p_pane_rect.size.x + TOLERANCE_PX and
+				screen.y >= p_pane_rect.position.y - TOLERANCE_PX and
+				screen.y <= p_pane_rect.position.y + p_pane_rect.size.y + TOLERANCE_PX)
 
 	####################################################################################################
 	# Per-instance custom data packing
@@ -757,20 +750,11 @@ class ScatterRenderer extends Control:
 			outline_color = _apply_alpha(_scatter_style.hovered_outline_color, alpha)
 
 		# Transform: translate to center, scale by size_px.
-		# map_x_to_px returns screen-Y when x is vertical, and map_y_to_px returns
-		# screen-X when x is vertical. The callers pass the x-axis pixel as p_cx
-		# and the y-axis pixel as p_cy, so we must swap them for vertical x.
-		var screen_x: float
-		var screen_y: float
-		if _layout._x_is_horizontal:
-			screen_x = p_cx
-			screen_y = p_cy
-		else:
-			screen_x = p_cy
-			screen_y = p_cx
+		# The callers pass the x-axis pixel as p_cx and the y-axis pixel as p_cy
+		var screen := _layout.map_point_to_screen(p_cx, p_cy)
 		var t := Transform2D()
 		t = t.scaled(Vector2(size_px, size_px))
-		t.origin = Vector2(screen_x, screen_y)
+		t.origin = screen
 		p_entry.mm.set_instance_transform_2d(p_slot, t)
 
 		# Color: fill color with alpha
@@ -783,7 +767,7 @@ class ScatterRenderer extends Control:
 		p_entry.mm.set_instance_custom_data(p_slot, _pack_custom_data(outline_color, shape, ow_norm))
 
 		# Record hover data for hit testing.
-		_hover_screen_positions.append(Vector2(screen_x, screen_y))
+		_hover_screen_positions.append(screen)
 		_hover_series_ids.append(series_id)
 		_hover_sample_indices.append(p_sample_index)
 		_hover_x_values.append(p_x_value)
diff --git a/addons/tau-plot/plot/xy/xy_layout.gd b/addons/tau-plot/plot/xy/xy_layout.gd
index f132764..3e69bf9 100644
--- a/addons/tau-plot/plot/xy/xy_layout.gd
+++ b/addons/tau-plot/plot/xy/xy_layout.gd
@@ -391,6 +391,32 @@ class XYLayout extends RefCounted:
 		return map_y_to_px(p_pane_index, 0.0, p_y_axis_id)
 
 
+	## Assembles a screen-space [Vector2] from two pixel coordinates that are
+	## already expressed along the x-axis and y-axis directions respectively.
+	##
+	## [param p_x_axis_px] Pixel coordinate along the x-axis direction, as
+	##                     returned by [method map_x_to_px] or
+	##                     [method map_x_category_center_to_px].
+	## [param p_y_axis_px] Pixel coordinate along the y-axis direction, as
+	##                     returned by [method map_y_to_px].
+	##
+	## When the x axis is horizontal, the x-axis direction is screen-X and
+	## the y-axis direction is screen-Y, so the values map straight through.
+	## When the x axis is vertical, the two are swapped.
+	##
+	## Note: both input values already encode axis inversion and scale
+	## (linear or logarithmic) because those are applied inside the
+	## mapping functions. This helper only performs the orientation swap.
+	func map_point_to_screen(p_x_axis_px: float, p_y_axis_px: float) -> Vector2:
+		if _x_is_horizontal:
+			return Vector2(p_x_axis_px, p_y_axis_px)
+		return Vector2(p_y_axis_px, p_x_axis_px)
+
+	func map_screen_to_point(p_screen_coords: Vector2) -> Vector2:
+		if _x_is_horizontal:
+			return Vector2(p_screen_coords.x, p_screen_coords.y)
+		return Vector2(p_screen_coords.y, p_screen_coords.x)
+
 	################################################################################################
 	# Categorical label visibility
 	################################################################################################

From fa9db6d3bc47a2d4e5132bf44d7468bc52f21d03 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Thu, 23 Apr 2026 17:33:17 +0100
Subject: [PATCH 02/23] Line overlay minimal implementation

---
 .../plot/xy/hover/hover_controller.gd         |   8 +
 addons/tau-plot/plot/xy/line/line_config.gd   |  97 +++++++
 .../tau-plot/plot/xy/line/line_config.gd.uid  |   1 +
 addons/tau-plot/plot/xy/line/line_renderer.gd | 273 ++++++++++++++++++
 .../plot/xy/line/line_renderer.gd.uid         |   1 +
 addons/tau-plot/plot/xy/line/line_style.gd    | 105 +++++++
 .../tau-plot/plot/xy/line/line_style.gd.uid   |   1 +
 .../tau-plot/plot/xy/line/line_validator.gd   |  61 ++++
 .../plot/xy/line/line_validator.gd.uid        |   1 +
 .../plot/xy/line/line_visual_attributes.gd    |   7 +
 .../xy/line/line_visual_attributes.gd.uid     |   1 +
 .../plot/xy/line/line_visual_callbacks.gd     |   7 +
 .../plot/xy/line/line_visual_callbacks.gd.uid |   1 +
 addons/tau-plot/plot/xy/pane_overlay_type.gd  |   2 +-
 addons/tau-plot/plot/xy/xy_plot.gd            | 140 ++++++++-
 addons/tau-plot/plot/xy/xy_plot_validator.gd  |  11 +
 addons/tau-plot/plot/xy/xy_state.gd           |  45 +++
 17 files changed, 758 insertions(+), 4 deletions(-)
 create mode 100644 addons/tau-plot/plot/xy/line/line_config.gd
 create mode 100644 addons/tau-plot/plot/xy/line/line_config.gd.uid
 create mode 100644 addons/tau-plot/plot/xy/line/line_renderer.gd
 create mode 100644 addons/tau-plot/plot/xy/line/line_renderer.gd.uid
 create mode 100644 addons/tau-plot/plot/xy/line/line_style.gd
 create mode 100644 addons/tau-plot/plot/xy/line/line_style.gd.uid
 create mode 100644 addons/tau-plot/plot/xy/line/line_validator.gd
 create mode 100644 addons/tau-plot/plot/xy/line/line_validator.gd.uid
 create mode 100644 addons/tau-plot/plot/xy/line/line_visual_attributes.gd
 create mode 100644 addons/tau-plot/plot/xy/line/line_visual_attributes.gd.uid
 create mode 100644 addons/tau-plot/plot/xy/line/line_visual_callbacks.gd
 create mode 100644 addons/tau-plot/plot/xy/line/line_visual_callbacks.gd.uid

diff --git a/addons/tau-plot/plot/xy/hover/hover_controller.gd b/addons/tau-plot/plot/xy/hover/hover_controller.gd
index d967542..f4f0772 100644
--- a/addons/tau-plot/plot/xy/hover/hover_controller.gd
+++ b/addons/tau-plot/plot/xy/hover/hover_controller.gd
@@ -9,6 +9,7 @@ const XYLayout := preload("res://addons/tau-plot/plot/xy/xy_layout.gd").XYLayout
 const PaneRenderer := preload("res://addons/tau-plot/plot/xy/pane_renderer.gd").PaneRenderer
 const BarRenderer := preload("res://addons/tau-plot/plot/xy/bar/bar_renderer.gd").BarRenderer
 const ScatterRenderer := preload("res://addons/tau-plot/plot/xy/scatter/scatter_renderer.gd").ScatterRenderer
+const LineRenderer := preload("res://addons/tau-plot/plot/xy/line/line_renderer.gd").LineRenderer
 
 
 ## Handles input dispatch, hover mode resolution, hit aggregation across
@@ -24,6 +25,7 @@ class HoverController extends RefCounted:
 	var _pane_renderers: Array[PaneRenderer] = []
 	var _bar_renderers: Array[BarRenderer] = []
 	var _scatter_renderers: Array[ScatterRenderer] = []
+	var _line_renderers: Array[LineRenderer] = []
 	var _resolved_xy_style: TauXYStyle = null
 
 	# Hover state.
@@ -58,6 +60,7 @@ class HoverController extends RefCounted:
 			p_pane_renderers: Array[PaneRenderer],
 			p_bar_renderers: Array[BarRenderer],
 			p_scatter_renderers: Array[ScatterRenderer],
+			p_line_renderers: Array[LineRenderer],
 			p_resolved_xy_style: TauXYStyle,
 			p_formatter: HoverFormatter,
 			p_hit_testers_per_pane: Array, # Array[Array[OverlayHitTester]] FIXME Godot 4.5 does not support nested typed collections.
@@ -70,6 +73,7 @@ class HoverController extends RefCounted:
 		_pane_renderers = p_pane_renderers
 		_bar_renderers = p_bar_renderers
 		_scatter_renderers = p_scatter_renderers
+		_line_renderers = p_line_renderers
 		_resolved_xy_style = p_resolved_xy_style
 		_formatter = p_formatter
 		_hit_testers_per_pane = p_hit_testers_per_pane
@@ -102,6 +106,7 @@ class HoverController extends RefCounted:
 		_pane_renderers = []
 		_bar_renderers = []
 		_scatter_renderers = []
+		_line_renderers = []
 		_resolved_xy_style = null
 		_formatter = null
 		_hover_config = null
@@ -574,6 +579,9 @@ class HoverController extends RefCounted:
 					var existing: SampleHit = scatter_hits_by_pane.get(hit.pane_index)
 					if existing == null or hit.distance_px < existing.distance_px:
 						scatter_hits_by_pane[hit.pane_index] = hit
+			elif hit.overlay_type == PaneOverlayType.LINE:
+				# TODO: categorize line hits once line hover is wired.
+				pass
 
 		for pane_index: int in range(_bar_renderers.size()):
 			var renderer: BarRenderer = _bar_renderers[pane_index]
diff --git a/addons/tau-plot/plot/xy/line/line_config.gd b/addons/tau-plot/plot/xy/line/line_config.gd
new file mode 100644
index 0000000..6cfb4c8
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_config.gd
@@ -0,0 +1,97 @@
+## Line-overlay specific rendering config.
+class_name TauLineConfig extends TauPaneOverlayConfig
+
+const LineVisualCallbacks := preload("res://addons/tau-plot/plot/xy/line/line_visual_callbacks.gd").LineVisualCallbacks
+
+################################################################################################
+# WARNING: Any new member added to this class must be reflected in `is_equal_to()`
+#          and, if applicable, in `has_layout_affecting_change()`.
+################################################################################################
+
+## Theme-driven visual parameters for lines.
+## Never null. Modify properties directly: line_config.style.line_width_px = 3.0.
+## Properties set this way are automatically guarded from theme overwriting.
+@export var style: TauLineStyle = TauLineStyle.new()
+
+enum LineMode
+{
+	INDEPENDENT,   ## Each series is drawn independently.
+	STACKED        ## Values at the same X are summed across series.
+}
+@export var mode: LineMode = LineMode.INDEPENDENT
+
+const StackedNormalization = preload("res://addons/tau-plot/plot/xy/stacked_normalization.gd").StackedNormalization
+@export var stacked_normalization: StackedNormalization = StackedNormalization.NONE
+
+## Maximum pixel distance from the cursor to a sample position for the sample
+## to be considered a hover hit.
+##
+## In NEAREST mode, this is a 2D Euclidean distance gate. Samples farther
+## than this value from the cursor are excluded entirely.
+##
+## In X_ALIGNED mode, this is an x-axis-only pixel gate. Samples whose x
+## screen position differs from the target x by more than this value are
+## excluded. The same threshold sets [member SampleHit.contains_pointer]
+## on included hits.
+@export var hover_max_distance_px: int = 10
+
+
+####################################################################################################
+# Typed visual_callbacks accessor
+####################################################################################################
+
+## Typed accessor for line-specific visual callbacks.
+## Shadows the base [member TauPaneOverlayConfig.visual_callbacks] with the concrete type.
+var line_visual_callbacks: LineVisualCallbacks:
+	get:
+		return visual_callbacks as LineVisualCallbacks
+	set(value):
+		visual_callbacks = value
+
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func _init() -> void:
+	overlay_type = PaneOverlayType.LINE
+
+
+func is_equal_to(p_other: TauPaneOverlayConfig) -> bool:
+	var other := p_other as TauLineConfig
+	if other == null:
+		return false
+
+	if not super.is_equal_to(other):
+		return false
+
+	if mode != other.mode:
+		return false
+	if stacked_normalization != other.stacked_normalization:
+		return false
+	if hover_max_distance_px != other.hover_max_distance_px:
+		return false
+
+	return true
+
+
+# Returns true if the change between this and p_other affects layout/domain.
+# Returns false if the change only affects visual appearance.
+#
+# Only mode and stacked_normalization affect the domain: stacking changes the
+# Y bounds. Hover distance is a pure hit-test parameter with no layout effect.
+func has_layout_affecting_change(p_other: TauPaneOverlayConfig) -> bool:
+	var other := p_other as TauLineConfig
+	if other == null:
+		return false
+
+	if not super.has_layout_affecting_change(other):
+		return false
+
+	if mode != other.mode:
+		return true
+
+	if mode == LineMode.STACKED and stacked_normalization != other.stacked_normalization:
+		return true
+
+	return false
diff --git a/addons/tau-plot/plot/xy/line/line_config.gd.uid b/addons/tau-plot/plot/xy/line/line_config.gd.uid
new file mode 100644
index 0000000..bf62a0d
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_config.gd.uid
@@ -0,0 +1 @@
+uid://cqwyag6rk1ekl
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
new file mode 100644
index 0000000..482a347
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -0,0 +1,273 @@
+# Dependencies
+const Dataset := preload("res://addons/tau-plot/model/dataset.gd").Dataset
+const XYLayout := preload("res://addons/tau-plot/plot/xy/xy_layout.gd").XYLayout
+const SeriesAxisAssignment := preload("res://addons/tau-plot/plot/xy/series_axis_assignment.gd").SeriesAxisAssignment
+const AxisId = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").AxisId
+const Axis = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").Axis
+const VisualAttributes = preload("res://addons/tau-plot/plot/xy/visual_attributes.gd").VisualAttributes
+const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_visual_attributes.gd").LineVisualAttributes
+
+
+# Draws line overlays from an XYLayout + Dataset.
+#
+# This renderer reads all samples through the Dataset public API (no direct
+# buffer/series access). One contiguous run of valid samples produces one
+# draw_polyline() call per series.
+#
+# Runtime behavior:
+# - NaN and Inf X or Y values break the polyline (SKIP gap policy).
+# - Logarithmic Y scales: y <= 0 breaks the polyline.
+# - Logarithmic X scales: x <= 0 breaks the polyline.
+#
+# LineValidator is expected to enforce binding-level typing constraints.
+class LineRenderer extends Control:
+	var _layout: XYLayout = null
+	var _dataset: Dataset = null
+	var _line_config: TauLineConfig = null
+	var _series_assignment: SeriesAxisAssignment = null
+	var _visual_attributes: Array[LineVisualAttributes] = []
+
+	# Pane index this renderer belongs to. Used for per-pane domain/layout queries.
+	var _pane_index: int = 0
+
+	# Line-specific series list: only series mapped as LINE are iterated.
+	# Must be provided at construction. Empty means this renderer has no
+	# series to draw.
+	var _line_series_ids: PackedInt64Array = PackedInt64Array()
+
+	# Resolved style instances pushed by xy_plot. Treat as read-only.
+	var _line_style: TauLineStyle = null
+	var _xy_style: TauXYStyle = null
+
+
+	func _init(p_layout: XYLayout,
+				p_dataset: Dataset,
+				p_line_config: TauLineConfig,
+				p_xy_style: TauXYStyle,
+				p_series_assignment: SeriesAxisAssignment,
+				p_pane_index: int = 0,
+				p_visual_attributes: Array[LineVisualAttributes] = [],
+				p_line_series_ids: PackedInt64Array = PackedInt64Array()) -> void:
+		theme_type_variation = &"TauLine"
+		_layout = p_layout
+		_dataset = p_dataset
+		_line_config = p_line_config
+		_series_assignment = p_series_assignment
+		_pane_index = p_pane_index
+		_visual_attributes = p_visual_attributes
+		_line_series_ids = p_line_series_ids
+		_line_style = p_line_config.style
+		_xy_style = p_xy_style
+
+
+	func _ready() -> void:
+		mouse_filter = Control.MOUSE_FILTER_IGNORE
+		queue_redraw()
+
+
+	func _notification(what: int) -> void:
+		match what:
+			NOTIFICATION_RESIZED:
+				queue_redraw()
+
+
+	func get_config() -> TauLineConfig:
+		return _line_config
+
+
+	## Receives the resolved TauLineStyle from xy_plot after cascade resolution.
+	func set_resolved_line_style(p_style: TauLineStyle) -> void:
+		_line_style = p_style
+
+
+	## Receives the resolved TauXYStyle from xy_plot after cascade resolution.
+	func set_resolved_xy_style(p_style: TauXYStyle) -> void:
+		_xy_style = p_style
+
+
+	## Creates a legend key Control for a line overlay.
+	func create_legend_key_control(_p_series_index: int) -> Control:
+		# TODO: implement create_legend_key_control for lines
+		return Control.new()
+
+
+	####################################################################################################
+	# Private
+	####################################################################################################
+
+	func _draw() -> void:
+		if _line_style == null:
+			push_error("LineRenderer: resolved TauLineStyle is null.")
+			return
+
+		var pane_rect := _layout.get_pane_rect(_pane_index)
+		if pane_rect.size.x <= 0.0 or pane_rect.size.y <= 0.0:
+			return
+
+		var series_count := _get_line_series_count()
+		if series_count <= 0:
+			return
+
+		var draw_order := _get_series_draw_order(series_count)
+		var width_px: float = max(_line_style.line_width_px, 0.0)
+		if width_px <= 0.0:
+			return
+
+		for draw_rank in range(draw_order.size()):
+			var series_index: int = draw_order[draw_rank]
+			_draw_series_independent(series_index, width_px)
+
+
+	# Draws a single series as one or more polyline runs, respecting SKIP
+	# gap policy. Run emission follows these rules:
+	#   - A valid sample is appended to the current run.
+	#   - An invalid sample (NaN/Inf X or Y, or a value forbidden by the
+	#     active axis scale) flushes the current run and starts a new one.
+	#   - A run of fewer than two points is discarded (no polyline).
+	func _draw_series_independent(p_series_index: int, p_width_px: float) -> void:
+		var x_cfg := _get_x_axis_config()
+		if x_cfg != null and x_cfg.type == TauAxisConfig.Type.CATEGORICAL:
+			_draw_series_categorical(p_series_index, p_width_px)
+		else:
+			_draw_series_continuous(p_series_index, p_width_px)
+
+
+	func _draw_series_continuous(p_series_index: int, p_width_px: float) -> void:
+		var series_id := _get_line_series_id(p_series_index)
+		var global_series_index := _get_global_series_index(p_series_index)
+		var color := _resolve_series_color(global_series_index)
+		var y_axis_id := _get_y_axis_id_for_series(series_id)
+
+		var run := PackedVector2Array()
+
+		var is_shared_x := _dataset.get_mode() == Dataset.Mode.SHARED_X
+		var sample_count := _dataset.get_series_sample_count(series_id)
+
+		for i in range(sample_count):
+			var x_value: float = float(_dataset.get_shared_x(i)) if is_shared_x else float(_dataset.get_series_x(series_id, i))
+			if is_nan(x_value) or is_inf(x_value) or not _is_x_value_valid_for_scale(x_value):
+				run = _flush_run(run, color, p_width_px)
+				continue
+
+			var y_value := _dataset.get_series_y(series_id, i)
+			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
+				run = _flush_run(run, color, p_width_px)
+				continue
+
+			var x_px := _layout.map_x_to_px(_pane_index, x_value)
+			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
+			run.append(_layout.map_point_to_screen(x_px, y_px))
+
+		if run.size() >= 2:
+			draw_polyline(run, color, p_width_px)
+
+
+	func _draw_series_categorical(p_series_index: int, p_width_px: float) -> void:
+		var series_id := _get_line_series_id(p_series_index)
+		var global_series_index := _get_global_series_index(p_series_index)
+		var color := _resolve_series_color(global_series_index)
+		var y_axis_id := _get_y_axis_id_for_series(series_id)
+
+		var run := PackedVector2Array()
+		var sample_count := _dataset.get_series_sample_count(series_id)
+
+		for cat_idx in range(sample_count):
+			var y_value := _dataset.get_series_y(series_id, cat_idx)
+			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
+				run = _flush_run(run, color, p_width_px)
+				continue
+
+			var x_px := _layout.map_x_category_center_to_px(_pane_index, cat_idx)
+			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
+			run.append(_layout.map_point_to_screen(x_px, y_px))
+
+		if run.size() >= 2:
+			draw_polyline(run, color, p_width_px)
+
+
+	func _flush_run(p_run: PackedVector2Array, p_color: Color, p_width_px: float) -> PackedVector2Array:
+		if p_run.size() >= 2:
+			draw_polyline(p_run, p_color, p_width_px)
+		return PackedVector2Array()
+
+
+	####################################################################################################
+	# Series helpers
+	####################################################################################################
+
+	# Returns the number of series this renderer is responsible for.
+	func _get_line_series_count() -> int:
+		return _line_series_ids.size()
+
+
+	# Returns the dataset series_id for a given line-local series index.
+	func _get_line_series_id(p_line_index: int) -> int:
+		return _line_series_ids[p_line_index]
+
+
+	# Returns the dataset-global series index for a given pane-local series index.
+	func _get_global_series_index(p_local_index: int) -> int:
+		return _dataset.get_series_index_by_id(_line_series_ids[p_local_index])
+
+
+	# Honors TauPaneOverlayConfig.z_order to decide which series is drawn on top.
+	func _get_series_draw_order(p_series_count: int) -> Array[int]:
+		var order: Array[int] = []
+		for i in range(p_series_count):
+			order.append(i)
+		if _line_config.z_order == TauPaneOverlayConfig.ZOrder.REVERSE_SERIES_ORDER:
+			order.reverse()
+		return order
+
+
+	# Returns the shared x axis config.
+	func _get_x_axis_config() -> TauAxisConfig:
+		return _layout.domain.config.x_axis
+
+
+	####################################################################################################
+	# Color resolution
+	####################################################################################################
+
+	# TODO: fully implement _resolve_series_color
+	func _resolve_series_color(p_global_series_index: int) -> Color:
+		var color := _xy_style.get_series_color(p_global_series_index)
+		color.a = clampf(_xy_style.series_alpha, 0.0, 1.0)
+		return color
+
+
+	####################################################################################################
+	# Axis helpers
+	####################################################################################################
+
+	func _get_y_axis_id_for_series(p_series_id: int) -> AxisId:
+		var axis_id: int = _series_assignment.get_y_axis_id_for_series(p_series_id, _pane_index)
+		if axis_id != -1:
+			return axis_id as AxisId
+		# Fallback: should not happen if validation passed.
+		push_error("LineRenderer: series %d not assigned to any y-axis in pane %d" % [p_series_id, _pane_index])
+		return Axis.get_orthogonal_axes(_layout.domain.config.x_axis_id)[0]
+
+
+	####################################################################################################
+	# Axis-scale validity checks
+	####################################################################################################
+
+	func _is_x_value_valid_for_scale(p_x_value: float) -> bool:
+		var x_cfg := _layout.domain.config.x_axis
+		if x_cfg == null:
+			return true
+		if x_cfg.scale == TauAxisConfig.Scale.LOGARITHMIC and p_x_value <= 0.0:
+			return false
+		return true
+
+
+	func _is_y_value_valid_for_scale(p_series_id: int, p_y_value: float) -> bool:
+		var y_axis_id := _get_y_axis_id_for_series(p_series_id)
+		var pane_cfg: TauPaneConfig = _layout.domain.config.panes[_pane_index]
+		var y_cfg: TauAxisConfig = pane_cfg.get_y_axis_config(y_axis_id)
+		if y_cfg == null:
+			return true
+		if y_cfg.scale == TauAxisConfig.Scale.LOGARITHMIC and p_y_value <= 0.0:
+			return false
+		return true
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd.uid b/addons/tau-plot/plot/xy/line/line_renderer.gd.uid
new file mode 100644
index 0000000..e2bbdb4
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd.uid
@@ -0,0 +1 @@
+uid://bjlgjhtxnkkv7
diff --git a/addons/tau-plot/plot/xy/line/line_style.gd b/addons/tau-plot/plot/xy/line/line_style.gd
new file mode 100644
index 0000000..9d90fe3
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_style.gd
@@ -0,0 +1,105 @@
+## Contains theme-driven visual parameters for line overlays.
+##
+## Properties set on this resource take the highest priority, always winning
+## over the theme and the built-in defaults.
+##
+## Properties left untouched fall back to the Godot theme. If the theme does
+## not define them either, the built-in defaults apply.
+##
+## [b]Limitation:[/b] because "untouched" means "still equal to the built-in
+## default", setting a property to exactly its default value has no visible
+## effect. To force the default value to win over a theme, use an imperceptibly
+## different value (e.g. 2.001 instead of 2.0).
+class_name TauLineStyle extends Resource
+
+################################################################################################
+# WARNING: Any new member added to this class must be reflected in `is_equal_to()`,
+#          `apply_overrides_from()`, and, if applicable, in
+#          `has_layout_affecting_change()`.
+################################################################################################
+
+const DEFAULT_LINE_WIDTH_PX: float = 2.0
+@export var line_width_px: float = DEFAULT_LINE_WIDTH_PX
+
+
+####################################################################################################
+# Cascade: theme loading (layer 2)
+####################################################################################################
+
+## Loads properties from the Godot theme attached to [param p_control].
+##
+## For each property, the non-indexed theme key is fetched first (shared base
+## for all panes), then the indexed key for [param p_pane_index] overwrites it
+## if present.
+##
+## This method writes every property unconditionally because it is called on
+## the resolved instance, not on the user-provided resource.
+func load_from_theme(p_control: Control, p_pane_index: int) -> void:
+	if p_control == null:
+		push_error("TauLineStyle.load_from_theme(): control is null")
+		return
+
+	# line_width_px
+	if p_control.has_theme_constant(&"line_width_px"):
+		line_width_px = max(float(p_control.get_theme_constant(&"line_width_px")), 0.0)
+	var indexed_width_key := StringName("line_width_px_%d" % p_pane_index)
+	if p_control.has_theme_constant(indexed_width_key):
+		line_width_px = max(float(p_control.get_theme_constant(indexed_width_key)), 0.0)
+
+
+####################################################################################################
+# Cascade: user overrides (layer 3)
+####################################################################################################
+
+## Applies overridden properties from [param p_user_style] onto this resolved
+## instance. A property is considered overridden when its value on the user
+## resource differs from the matching DEFAULT_* constant.
+func apply_overrides_from(p_user_style: TauLineStyle) -> void:
+	if p_user_style == null:
+		return
+
+	if p_user_style.line_width_px != DEFAULT_LINE_WIDTH_PX:
+		line_width_px = p_user_style.line_width_px
+
+
+####################################################################################################
+# Full cascade resolution
+####################################################################################################
+
+## Produces a fully resolved TauLineStyle by applying all three cascade layers:
+##   1. Start from defaults (a fresh TauLineStyle instance).
+##   2. Load theme values (non-indexed, then indexed for this pane).
+##   3. Apply user overrides from [param p_user_style] (may be null).
+##
+## The returned instance is a new TauLineStyle owned by the caller. It is
+## separate from [param p_user_style] which is never mutated.
+static func resolve(
+	p_control: Control,
+	p_pane_index: int,
+	p_user_style: TauLineStyle
+) -> TauLineStyle:
+	# Layer 1: defaults.
+	var resolved := TauLineStyle.new()
+	# Layer 2: theme values.
+	resolved.load_from_theme(p_control, p_pane_index)
+	# Layer 3: user overrides.
+	resolved.apply_overrides_from(p_user_style)
+	return resolved
+
+
+####################################################################################################
+# Change detection
+####################################################################################################
+
+func is_equal_to(p_other: TauLineStyle) -> bool:
+	if p_other == null:
+		return false
+	if line_width_px != p_other.line_width_px:
+		return false
+	return true
+
+
+# All TauLineStyle properties are visual-only. They control how lines are
+# drawn within a fixed domain but do not affect domain, ticks, or pane rect.
+func has_layout_affecting_change(p_other: TauLineStyle) -> bool:
+	return false
diff --git a/addons/tau-plot/plot/xy/line/line_style.gd.uid b/addons/tau-plot/plot/xy/line/line_style.gd.uid
new file mode 100644
index 0000000..151e788
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_style.gd.uid
@@ -0,0 +1 @@
+uid://hqhsstnn7m2q
diff --git a/addons/tau-plot/plot/xy/line/line_validator.gd b/addons/tau-plot/plot/xy/line/line_validator.gd
new file mode 100644
index 0000000..fc919d6
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_validator.gd
@@ -0,0 +1,61 @@
+# Dependencies
+const Dataset := preload("res://addons/tau-plot/model/dataset.gd").Dataset
+const PaneOverlayType = preload("res://addons/tau-plot/plot/xy/pane_overlay_type.gd").PaneOverlayType
+const LineVisualAttributes = preload("res://addons/tau-plot/plot/xy/line/line_visual_attributes.gd").LineVisualAttributes
+const LineVisualCallbacks = preload("res://addons/tau-plot/plot/xy/line/line_visual_callbacks.gd").LineVisualCallbacks
+const ValidationResult = preload("res://addons/tau-plot/plot/validation_result.gd").ValidationResult
+
+
+## Validates that the line overlay configuration for a single pane is
+## internally consistent.
+##
+## This validator checks configuration only, not dataset values. The dataset
+## is mutable after plot_xy() is called, so runtime data issues are handled
+## elsewhere.
+##
+## All errors are accumulated into the provided [ValidationResult].
+class LineValidator extends RefCounted:
+
+	static func validate(p_dataset: Dataset, p_domain_cfg: TauXYConfig, p_pane_index: int, p_line_overlay_bindings: Array[TauXYSeriesBinding], p_result: ValidationResult) -> void:
+		if p_dataset == null:
+			p_result.add_error("LineValidator: p_dataset is null")
+			return
+		if p_domain_cfg == null:
+			p_result.add_error("LineValidator: p_domain_cfg is null")
+			return
+		if p_pane_index < 0 or p_pane_index >= p_domain_cfg.panes.size():
+			p_result.add_error("LineValidator: p_pane_index %d is out of range" % p_pane_index)
+			return
+		for binding in p_line_overlay_bindings:
+			if binding.pane_index != p_pane_index:
+				p_result.add_error("LineValidator: binding has pane_index %d, expected %d" % [binding.pane_index, p_pane_index])
+				return
+			if binding.overlay_type != PaneOverlayType.LINE:
+				p_result.add_error("LineValidator: binding has overlay_type %d, expected LINE" % int(binding.overlay_type))
+				return
+
+		var pane_cfg := p_domain_cfg.panes[p_pane_index]
+		if pane_cfg == null:
+			p_result.add_error("LineValidator: pane %d: pane config is null" % p_pane_index)
+			return
+
+		var line_config := pane_cfg.get_overlay_config(PaneOverlayType.LINE) as TauLineConfig
+		if line_config == null:
+			p_result.add_error("LineValidator: pane %d: no TauLineConfig found in pane overlays" % p_pane_index)
+			return
+
+		_validate_line_visuals(p_pane_index, line_config, p_line_overlay_bindings, p_result)
+
+
+	####################################################################################################
+	# Private
+	####################################################################################################
+
+	static func _validate_line_visuals(p_pane_index: int, p_line_config: TauPaneOverlayConfig, p_line_overlay_bindings: Array[TauXYSeriesBinding], p_result: ValidationResult) -> void:
+		if p_line_config.visual_callbacks != null and p_line_config.visual_callbacks is not LineVisualCallbacks:
+			p_result.add_error("LineValidator: pane %d: visual_callbacks is not a LineVisualCallbacks" % p_pane_index)
+
+		for i in range(0, p_line_overlay_bindings.size()):
+			var binding: TauXYSeriesBinding = p_line_overlay_bindings[i]
+			if binding.visual_attributes != null and binding.visual_attributes is not LineVisualAttributes:
+				p_result.add_error("LineValidator: pane %d: series_id %d has visual_attributes that is not a LineVisualAttributes" % [p_pane_index, binding.series_id])
diff --git a/addons/tau-plot/plot/xy/line/line_validator.gd.uid b/addons/tau-plot/plot/xy/line/line_validator.gd.uid
new file mode 100644
index 0000000..ee741ac
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_validator.gd.uid
@@ -0,0 +1 @@
+uid://de3ehu51x06k1
diff --git a/addons/tau-plot/plot/xy/line/line_visual_attributes.gd b/addons/tau-plot/plot/xy/line/line_visual_attributes.gd
new file mode 100644
index 0000000..83c9efa
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_visual_attributes.gd
@@ -0,0 +1,7 @@
+# Dependencies
+const VisualAttributes = preload("res://addons/tau-plot/plot/xy/visual_attributes.gd").VisualAttributes
+
+## Per-sample data-driven visual attribute buffers for LINE overlays.
+class LineVisualAttributes extends VisualAttributes:
+	# TODO: add width_buffer.
+	pass
diff --git a/addons/tau-plot/plot/xy/line/line_visual_attributes.gd.uid b/addons/tau-plot/plot/xy/line/line_visual_attributes.gd.uid
new file mode 100644
index 0000000..d8b1ecc
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_visual_attributes.gd.uid
@@ -0,0 +1 @@
+uid://dhgf2p6cr42ll
diff --git a/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd b/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd
new file mode 100644
index 0000000..992b214
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd
@@ -0,0 +1,7 @@
+# Dependencies
+const VisualCallbacks = preload("res://addons/tau-plot/plot/xy/visual_callbacks.gd").VisualCallbacks
+
+## LINE overlay specific callbacks.
+class LineVisualCallbacks extends VisualCallbacks:
+	# TODO: add width_callback.
+	pass
diff --git a/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd.uid b/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd.uid
new file mode 100644
index 0000000..e3929fa
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd.uid
@@ -0,0 +1 @@
+uid://d4aien3nhx311
diff --git a/addons/tau-plot/plot/xy/pane_overlay_type.gd b/addons/tau-plot/plot/xy/pane_overlay_type.gd
index 3503024..cd67fa3 100644
--- a/addons/tau-plot/plot/xy/pane_overlay_type.gd
+++ b/addons/tau-plot/plot/xy/pane_overlay_type.gd
@@ -2,5 +2,5 @@ enum PaneOverlayType
 {
 	BAR = 0,
 	SCATTER,
-	# Future: LINE, AREA, etc.
+	LINE,
 }
diff --git a/addons/tau-plot/plot/xy/xy_plot.gd b/addons/tau-plot/plot/xy/xy_plot.gd
index c0acb12..096d4d2 100644
--- a/addons/tau-plot/plot/xy/xy_plot.gd
+++ b/addons/tau-plot/plot/xy/xy_plot.gd
@@ -41,6 +41,9 @@ const ScatterRenderer := preload("res://addons/tau-plot/plot/xy/scatter/scatter_
 const ScatterVisualAttributes = preload("res://addons/tau-plot/plot/xy/scatter/scatter_visual_attributes.gd").ScatterVisualAttributes
 const ScatterHitTester = preload("res://addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd").ScatterHitTester
 
+const LineRenderer := preload("res://addons/tau-plot/plot/xy/line/line_renderer.gd").LineRenderer
+const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_visual_attributes.gd").LineVisualAttributes
+
 
 # External references (provided via setup)
 var _plot: PanelContainer = null
@@ -60,6 +63,7 @@ var _xy_domain_overrides: XYDomainOverrides = null
 var _xy_layout: XYLayout = null
 var _bar_config_per_pane: Array[TauBarConfig] = []			# Elements may be null, one per pane
 var _scatter_config_per_pane: Array[TauScatterConfig] = []	# Elements may be null, one per pane
+var _line_config_per_pane: Array[TauLineConfig] = []		# Elements may be null, one per pane
 var _series_bindings: Array[TauXYSeriesBinding] = []
 var _series_assignment: SeriesAxisAssignment = null
 
@@ -67,9 +71,9 @@ var _series_assignment: SeriesAxisAssignment = null
 var _pane_renderers: Array[PaneRenderer] = []		# Elements are never null, one per pane
 var _bar_renderers: Array[BarRenderer] = []			# Elements may be null, one per pane
 var _scatter_renderers: Array[ScatterRenderer] = []	# Elements may be null, one per pane
+var _line_renderers: Array[LineRenderer] = []		# Elements may be null, one per pane
 
-# The BoxContainer that holds all pane containers. Created as VBoxContainer
-# (x horizontal) or HBoxContainer (x vertical) by _create_pane_stack().
+# The BoxContainer that holds all pane containers.
 var _pane_stack: BoxContainer = null
 
 # Per-pane containers (nodes inside _pane_stack)
@@ -78,6 +82,7 @@ var _pane_containers: Array[Container] = []			# Elements are never null, one per
 # Per-pane series partitioning
 var _bar_series_ids_per_pane: Array[PackedInt64Array] = []
 var _scatter_series_ids_per_pane: Array[PackedInt64Array] = []
+var _line_series_ids_per_pane: Array[PackedInt64Array] = []
 
 # Per-pane resolved TauPaneStyle instances (produced by the three-layer cascade).
 # One entry per pane, always non-null after setup().
@@ -86,6 +91,7 @@ var _resolved_pane_styles: Array[TauPaneStyle] = []
 # Per-pane resolved overlay style instances (produced by the three-layer cascade).
 var _resolved_bar_styles: Array[TauBarStyle] = []
 var _resolved_scatter_styles: Array[TauScatterStyle] = []
+var _resolved_line_styles: Array[TauLineStyle] = []
 
 # Plot-wide resolved TauXYStyle instance (produced by the three-layer cascade).
 # Distributed to all renderers (PaneRenderer, BarRenderer, ScatterRenderer).
@@ -111,6 +117,7 @@ var _styles_dirty: bool = true
 var _xy_dirty_panes: Array[bool] = []
 var _bars_dirty_panes: Array[bool] = []
 var _scatter_dirty_panes: Array[bool] = []
+var _line_dirty_panes: Array[bool] = []
 
 # Hover controller (null when setup() has not been called or hover is not wired)
 var _hover_controller: HoverController = null
@@ -153,15 +160,21 @@ func setup(
 	_bar_config_per_pane.fill(null)
 	_scatter_config_per_pane.resize(pane_count)
 	_scatter_config_per_pane.fill(null)
+	_line_config_per_pane.resize(pane_count)
+	_line_config_per_pane.fill(null)
 	_bar_series_ids_per_pane.clear()
 	_scatter_series_ids_per_pane.clear()
+	_line_series_ids_per_pane.clear()
 	var bar_va_per_pane: Array = []     # Array of Array[BarVisualAttributes]. FIXME Godot 4.5 does not support nested typed collections.
 	var scatter_va_per_pane: Array = [] # Array of Array[ScatterVisualAttributes]. FIXME Godot 4.5 does not support nested typed collections.
+	var line_va_per_pane: Array = []    # Array of Array[LineVisualAttributes]. FIXME Godot 4.5 does not support nested typed collections.
 	for i in range(pane_count):
 		_bar_series_ids_per_pane.append(PackedInt64Array())
 		_scatter_series_ids_per_pane.append(PackedInt64Array())
+		_line_series_ids_per_pane.append(PackedInt64Array())
 		bar_va_per_pane.append([] as Array[BarVisualAttributes])
 		scatter_va_per_pane.append([] as Array[ScatterVisualAttributes])
+		line_va_per_pane.append([] as Array[LineVisualAttributes])
 
 	# Extract series bindings
 	_series_assignment = SeriesAxisAssignment.new(pane_count)
@@ -199,6 +212,20 @@ func setup(
 					# Type is guaranteed by validation (ScatterValidator._validate_scatter_visuals).
 					scatter_va_per_pane[pane_index].append(binding.visual_attributes as ScatterVisualAttributes)
 
+			TauXYSeriesBinding.PaneOverlayType.LINE:
+				if sid not in _line_series_ids_per_pane[pane_index]:
+					_line_series_ids_per_pane[pane_index].append(sid)
+
+				if _line_config_per_pane[pane_index] == null:
+					var pane_config: TauPaneConfig = p_xy_config.panes[pane_index]
+					var line_cfg := pane_config.get_overlay_config(TauXYSeriesBinding.PaneOverlayType.LINE) as TauLineConfig
+					if line_cfg != null:
+						_line_config_per_pane[pane_index] = line_cfg
+
+				if binding.visual_attributes != null:
+					# Type is guaranteed by validation (LineValidator._validate_line_visuals).
+					line_va_per_pane[pane_index].append(binding.visual_attributes as LineVisualAttributes)
+
 			_:
 				# Unknown overlay types are rejected by validation.
 				pass
@@ -217,6 +244,8 @@ func setup(
 			_bar_config_per_pane[pane_index].style.changed.connect(_on_style_changed)
 		if _scatter_config_per_pane[pane_index] != null and not _scatter_config_per_pane[pane_index].style.changed.is_connected(_on_style_changed):
 			_scatter_config_per_pane[pane_index].style.changed.connect(_on_style_changed)
+		if _line_config_per_pane[pane_index] != null and not _line_config_per_pane[pane_index].style.changed.is_connected(_on_style_changed):
+			_line_config_per_pane[pane_index].style.changed.connect(_on_style_changed)
 		var pane_config: TauPaneConfig = p_xy_config.panes[pane_index]
 		if pane_config.style != null and not pane_config.style.changed.is_connected(_on_style_changed):
 			pane_config.style.changed.connect(_on_style_changed)
@@ -230,16 +259,20 @@ func setup(
 	_pane_renderers.clear()
 	_bar_renderers.clear()
 	_scatter_renderers.clear()
+	_line_renderers.clear()
 	_resolved_pane_styles.clear()
 	_resolved_bar_styles.clear()
 	_resolved_scatter_styles.clear()
+	_resolved_line_styles.clear()
 
 	_pane_renderers.resize(pane_count)
 	_bar_renderers.resize(pane_count)
 	_scatter_renderers.resize(pane_count)
+	_line_renderers.resize(pane_count)
 	_resolved_pane_styles.resize(pane_count)
 	_resolved_bar_styles.resize(pane_count)
 	_resolved_scatter_styles.resize(pane_count)
+	_resolved_line_styles.resize(pane_count)
 	_pane_containers.resize(pane_count)
 
 	# Resolve TauXYStyle cascade once against the TauPlot root so that theme
@@ -310,6 +343,24 @@ func setup(
 			scatter_renderer.set_resolved_scatter_style(resolved_scatter_style)
 			scatter_renderer.set_resolved_xy_style(_resolved_xy_style)
 
+		# Create LineRenderer for this pane if it has line series
+		if not _line_series_ids_per_pane[pane_index].is_empty():
+			var line_renderer := LineRenderer.new(
+				_xy_layout, _dataset, _line_config_per_pane[pane_index], p_xy_config.style,
+				_series_assignment,
+				pane_index, line_va_per_pane[pane_index],
+				_line_series_ids_per_pane[pane_index])
+			pane_container.add_child(line_renderer)
+			line_renderer.set_anchors_and_offsets_preset(Control.PRESET_FULL_RECT)
+			_line_renderers[pane_index] = line_renderer
+
+			# Resolve TauLineStyle cascade and push it to the renderer.
+			var line_user_style: TauLineStyle = _line_config_per_pane[pane_index].style
+			var resolved_line_style := TauLineStyle.resolve(line_renderer, pane_index, line_user_style)
+			_resolved_line_styles[pane_index] = resolved_line_style
+			line_renderer.set_resolved_line_style(resolved_line_style)
+			line_renderer.set_resolved_xy_style(_resolved_xy_style)
+
 	# Axis titles
 	_axis_title_layout.build(p_xy_config, _series_assignment)
 
@@ -365,7 +416,7 @@ func setup(
 	_hover_controller.setup(
 		_plot, _xy_layout, _domain_config,
 		_pane_containers, _pane_renderers,
-		_bar_renderers, _scatter_renderers,
+		_bar_renderers, _scatter_renderers, _line_renderers,
 		_resolved_xy_style, formatter, hit_testers_per_pane,
 		p_hover_enabled, p_hover_config)
 
@@ -389,11 +440,14 @@ func clear() -> void:
 	_series_assignment = null
 	_bar_config_per_pane.clear()
 	_scatter_config_per_pane.clear()
+	_line_config_per_pane.clear()
 	_bar_series_ids_per_pane.clear()
 	_scatter_series_ids_per_pane.clear()
+	_line_series_ids_per_pane.clear()
 	_resolved_pane_styles.clear()
 	_resolved_bar_styles.clear()
 	_resolved_scatter_styles.clear()
+	_resolved_line_styles.clear()
 	_resolved_xy_style = null
 	_resolved_legend_style = null
 	_user_legend_style = null
@@ -490,6 +544,30 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 					_scatter_dirty_panes[pane_index] = true
 				_state.save_scatter_config_for_pane(pane_index, pane_scatter_config)
 
+	# Step 3-line: Check if line config changed per pane
+	var has_any_line := false
+	for renderer in _line_renderers:
+		if renderer != null:
+			has_any_line = true
+			break
+
+	if has_any_line:
+		for pane_index in range(pane_count):
+			var pane_line_config: TauLineConfig = _line_config_per_pane[pane_index] if pane_index < _line_config_per_pane.size() else null
+			if pane_line_config == null:
+				continue
+			var prev_line_config: TauLineConfig = _state.line_config_per_pane[pane_index] if pane_index < _state.line_config_per_pane.size() else null
+			if not pane_line_config.is_equal_to(prev_line_config):
+				if pane_line_config.has_layout_affecting_change(prev_line_config):
+					_domain_dirty = true
+					_ticks_dirty = true
+					_pane_rect_dirty = true
+					_set_all_pane_flags(_xy_dirty_panes, true)
+					_set_all_pane_flags(_line_dirty_panes, true)
+				else:
+					_line_dirty_panes[pane_index] = true
+				_state.save_line_config_for_pane(pane_index, pane_line_config)
+
 	# Step 3b: Check if styles changed (programmatic mutations via config.style.*)
 	# XY style: three-layer change detection (theme dirty, ref change, content mutation).
 	#  - layout-affecting properties trigger ticks + pane rect recompute,
@@ -524,6 +602,9 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 			for renderer in _scatter_renderers:
 				if renderer != null:
 					renderer.set_resolved_xy_style(_resolved_xy_style)
+			for renderer in _line_renderers:
+				if renderer != null:
+					renderer.set_resolved_xy_style(_resolved_xy_style)
 
 			# Legend keys read visual properties from renderer instances.
 			# When the resolved TauXYStyle changes (colors, alpha), keys become stale.
@@ -595,6 +676,34 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 				_scatter_dirty_panes[pane_index] = true
 				_legend_rebuild_needed = true
 
+	# Line style: three-layer change detection (theme dirty, ref change, content mutation).
+	# All TauLineStyle properties are visual-only, so only dirty the owning line pane.
+	if has_any_line:
+		for pane_index in range(pane_count):
+			var line_config: TauLineConfig = _line_config_per_pane[pane_index] if pane_index < _line_config_per_pane.size() else null
+			if line_config == null:
+				continue
+			var needs_line_re_resolve := _styles_dirty
+
+			# Reference change: user assigned a different TauLineStyle resource.
+			if _state.has_line_style_ref_changed_for_pane(pane_index, line_config.style):
+				needs_line_re_resolve = true
+				_state.save_line_style_ref_for_pane(pane_index, line_config.style)
+
+			# Content mutation: user changed a property on the existing TauLineStyle.
+			if not needs_line_re_resolve:
+				var prev_line_style: TauLineStyle = _state.line_style_per_pane[pane_index] if pane_index < _state.line_style_per_pane.size() else null
+				if not line_config.style.is_equal_to(prev_line_style):
+					needs_line_re_resolve = true
+
+			if needs_line_re_resolve and _line_renderers[pane_index] != null:
+				var resolved_line := TauLineStyle.resolve(_line_renderers[pane_index], pane_index, line_config.style)
+				_resolved_line_styles[pane_index] = resolved_line
+				_line_renderers[pane_index].set_resolved_line_style(resolved_line)
+				_state.save_line_style_for_pane(pane_index, line_config.style)
+				_line_dirty_panes[pane_index] = true
+				_legend_rebuild_needed = true
+
 	# Step 3c: Check grid_line config changes, style reference changes,
 	# and pane style mutations. All visual-only.
 	for pane_index in range(pane_count):
@@ -724,6 +833,9 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 		if _scatter_dirty_panes[i] and _scatter_renderers[i] != null:
 			_scatter_renderers[i].update_scatter()
 			_scatter_dirty_panes[i] = false
+		if _line_dirty_panes[i] and _line_renderers[i] != null:
+			_line_renderers[i].queue_redraw()
+			_line_dirty_panes[i] = false
 
 	_state.save_pane_view_rects(pane_view_rects)
 
@@ -790,6 +902,11 @@ func _get_legend_key_factory(p_overlay_type: int, p_pane_index: int) -> Callable
 				var r = _scatter_renderers[p_pane_index]
 				if r != null:
 					return r.create_legend_key_control
+		TauXYSeriesBinding.PaneOverlayType.LINE:
+			if p_pane_index >= 0 and p_pane_index < _line_renderers.size():
+				var r = _line_renderers[p_pane_index]
+				if r != null:
+					return r.create_legend_key_control
 	return Callable()
 
 
@@ -820,9 +937,11 @@ func _init_pane_dirty_flags(p_pane_count: int) -> void:
 	_xy_dirty_panes.resize(p_pane_count)
 	_bars_dirty_panes.resize(p_pane_count)
 	_scatter_dirty_panes.resize(p_pane_count)
+	_line_dirty_panes.resize(p_pane_count)
 	_xy_dirty_panes.fill(true)
 	_bars_dirty_panes.fill(true)
 	_scatter_dirty_panes.fill(true)
+	_line_dirty_panes.fill(true)
 
 
 func _set_all_pane_flags(p_flags: Array[bool], p_value: bool) -> void:
@@ -846,17 +965,20 @@ func _mark_domain_dependents_dirty() -> void:
 	_set_all_pane_flags(_xy_dirty_panes, true)
 	_set_all_pane_flags(_bars_dirty_panes, true)
 	_set_all_pane_flags(_scatter_dirty_panes, true)
+	_set_all_pane_flags(_line_dirty_panes, true)
 
 
 func _mark_renderers_dirty() -> void:
 	_set_all_pane_flags(_bars_dirty_panes, true)
 	_set_all_pane_flags(_scatter_dirty_panes, true)
+	_set_all_pane_flags(_line_dirty_panes, true)
 
 
 func _mark_visual_dirty() -> void:
 	_set_all_pane_flags(_xy_dirty_panes, true)
 	_set_all_pane_flags(_bars_dirty_panes, true)
 	_set_all_pane_flags(_scatter_dirty_panes, true)
+	_set_all_pane_flags(_line_dirty_panes, true)
 
 
 func _reset_dataset() -> void:
@@ -879,6 +1001,10 @@ func _disconnect_style_signals() -> void:
 		if scatter_cfg != null and scatter_cfg.style != null:
 			if scatter_cfg.style.changed.is_connected(_on_style_changed):
 				scatter_cfg.style.changed.disconnect(_on_style_changed)
+	for line_cfg in _line_config_per_pane:
+		if line_cfg != null and line_cfg.style != null:
+			if line_cfg.style.changed.is_connected(_on_style_changed):
+				line_cfg.style.changed.disconnect(_on_style_changed)
 	if _domain_config != null:
 		for pane_config in _domain_config.panes:
 			if pane_config != null and pane_config.style != null:
@@ -914,6 +1040,9 @@ func _has_any_data_renderer() -> bool:
 	for renderer in _scatter_renderers:
 		if renderer != null:
 			return true
+	for renderer in _line_renderers:
+		if renderer != null:
+			return true
 	return false
 
 
@@ -933,6 +1062,11 @@ func _clear_pane_containers() -> void:
 			renderer.queue_free()
 	_scatter_renderers.clear()
 
+	for renderer in _line_renderers:
+		if renderer != null and is_instance_valid(renderer):
+			renderer.queue_free()
+	_line_renderers.clear()
+
 	if _pane_stack != null:
 		for container in _pane_containers:
 			if container != null and is_instance_valid(container):
diff --git a/addons/tau-plot/plot/xy/xy_plot_validator.gd b/addons/tau-plot/plot/xy/xy_plot_validator.gd
index ced18c0..4b6ab72 100644
--- a/addons/tau-plot/plot/xy/xy_plot_validator.gd
+++ b/addons/tau-plot/plot/xy/xy_plot_validator.gd
@@ -2,6 +2,7 @@
 const Dataset := preload("res://addons/tau-plot/model/dataset.gd").Dataset
 const BarValidator := preload("res://addons/tau-plot/plot/xy/bar/bar_validator.gd").BarValidator
 const ScatterValidator := preload("res://addons/tau-plot/plot/xy/scatter/scatter_validator.gd").ScatterValidator
+const LineValidator := preload("res://addons/tau-plot/plot/xy/line/line_validator.gd").LineValidator
 const Axis = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").Axis
 const AxisId = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").AxisId
 const ValidationResult = preload("res://addons/tau-plot/plot/validation_result.gd").ValidationResult
@@ -263,6 +264,7 @@ class XYPlotValidator extends RefCounted:
 		# Group series by overlay type and pane
 		var bar_bindings_by_pane: Dictionary[int, Array] = {}   # Array[TauXYSeriesBinding]. FIXME Godot 4.5 does not support nested typed collections.
 		var scatter_bindings_by_pane: Dictionary[int, Array] = {} # Array[TauXYSeriesBinding]. FIXME Godot 4.5 does not support nested typed collections.
+		var line_bindings_by_pane: Dictionary[int, Array] = {} # Array[TauXYSeriesBinding]. FIXME Godot 4.5 does not support nested typed collections.
 
 		for binding in p_series_bindings:
 			match binding.overlay_type:
@@ -274,6 +276,10 @@ class XYPlotValidator extends RefCounted:
 					if not scatter_bindings_by_pane.has(binding.pane_index):
 						scatter_bindings_by_pane[binding.pane_index] = []
 					scatter_bindings_by_pane[binding.pane_index].append(binding)
+				TauXYSeriesBinding.PaneOverlayType.LINE:
+					if not line_bindings_by_pane.has(binding.pane_index):
+						line_bindings_by_pane[binding.pane_index] = []
+					line_bindings_by_pane[binding.pane_index].append(binding)
 				_:
 					p_result.add_error("XYPlotValidator: unsupported overlay_type %d" % int(binding.overlay_type))
 
@@ -287,6 +293,11 @@ class XYPlotValidator extends RefCounted:
 			scatter_overlay_bindings.assign(scatter_bindings_by_pane[pane_index])
 			ScatterValidator.validate(p_dataset, p_xy_config, pane_index, scatter_overlay_bindings, p_result)
 
+		for pane_index in line_bindings_by_pane:
+			var line_overlay_bindings: Array[TauXYSeriesBinding] = []
+			line_overlay_bindings.assign(line_bindings_by_pane[pane_index])
+			LineValidator.validate(p_dataset, p_xy_config, pane_index, line_overlay_bindings, p_result)
+
 
 	####################################################################################################
 	# Warnings
diff --git a/addons/tau-plot/plot/xy/xy_state.gd b/addons/tau-plot/plot/xy/xy_state.gd
index b21efa1..b0f8790 100644
--- a/addons/tau-plot/plot/xy/xy_state.gd
+++ b/addons/tau-plot/plot/xy/xy_state.gd
@@ -78,6 +78,7 @@ class XYState extends RefCounted:
 	# Per-pane config snapshots from last refresh
 	var bar_config_per_pane: Array[TauBarConfig] = []
 	var scatter_config_per_pane: Array[TauScatterConfig] = []
+	var line_config_per_pane: Array[TauLineConfig] = []
 
 	# Per-pane grid_line config snapshots
 	var grid_line_config_per_pane: Array[TauGridLineConfig] = []
@@ -94,11 +95,13 @@ class XYState extends RefCounted:
 	var xy_style_ref: TauXYStyle = null
 	var bar_style_per_pane: Array[TauBarStyle] = []
 	var scatter_style_per_pane: Array[TauScatterStyle] = []
+	var line_style_per_pane: Array[TauLineStyle] = []
 
 	# Per-pane overlay style resource references (for detecting when the user
 	# assigns a different style resource to the config).
 	var bar_style_ref_per_pane: Array = []
 	var scatter_style_ref_per_pane: Array = []
+	var line_style_ref_per_pane: Array = []
 
 	# TauLegendStyle ref + content tracking
 	var legend_style_ref: TauLegendStyle = null
@@ -126,6 +129,11 @@ class XYState extends RefCounted:
 		while scatter_config_per_pane.size() < p_pane_count:
 			scatter_config_per_pane.append(null)
 
+		while line_config_per_pane.size() > p_pane_count:
+			line_config_per_pane.pop_back()
+		while line_config_per_pane.size() < p_pane_count:
+			line_config_per_pane.append(null)
+
 		while grid_line_config_per_pane.size() > p_pane_count:
 			grid_line_config_per_pane.pop_back()
 		while grid_line_config_per_pane.size() < p_pane_count:
@@ -151,6 +159,11 @@ class XYState extends RefCounted:
 		while scatter_style_per_pane.size() < p_pane_count:
 			scatter_style_per_pane.append(null)
 
+		while line_style_per_pane.size() > p_pane_count:
+			line_style_per_pane.pop_back()
+		while line_style_per_pane.size() < p_pane_count:
+			line_style_per_pane.append(null)
+
 		while bar_style_ref_per_pane.size() > p_pane_count:
 			bar_style_ref_per_pane.pop_back()
 		while bar_style_ref_per_pane.size() < p_pane_count:
@@ -161,6 +174,11 @@ class XYState extends RefCounted:
 		while scatter_style_ref_per_pane.size() < p_pane_count:
 			scatter_style_ref_per_pane.append(null)
 
+		while line_style_ref_per_pane.size() > p_pane_count:
+			line_style_ref_per_pane.pop_back()
+		while line_style_ref_per_pane.size() < p_pane_count:
+			line_style_ref_per_pane.append(null)
+
 
 	func reset() -> void:
 		domain_x_min = INF
@@ -176,6 +194,7 @@ class XYState extends RefCounted:
 
 		bar_config_per_pane.clear()
 		scatter_config_per_pane.clear()
+		line_config_per_pane.clear()
 
 		grid_line_config_per_pane.clear()
 		pane_style_ref_per_pane.clear()
@@ -185,9 +204,11 @@ class XYState extends RefCounted:
 		xy_style_ref = null
 		bar_style_per_pane.clear()
 		scatter_style_per_pane.clear()
+		line_style_per_pane.clear()
 
 		bar_style_ref_per_pane.clear()
 		scatter_style_ref_per_pane.clear()
+		line_style_ref_per_pane.clear()
 
 		legend_style_ref = null
 		legend_style_snapshot = null
@@ -321,6 +342,12 @@ class XYState extends RefCounted:
 		scatter_config_per_pane[p_pane_index] = p_scatter_config.duplicate() if p_scatter_config != null else null
 
 
+	func save_line_config_for_pane(p_pane_index: int, p_line_config: TauLineConfig) -> void:
+		if p_pane_index < 0 or p_pane_index >= line_config_per_pane.size():
+			return
+		line_config_per_pane[p_pane_index] = p_line_config.duplicate() if p_line_config != null else null
+
+
 	func save_grid_line_config_for_pane(p_pane_index: int, p_grid_line_config: TauGridLineConfig) -> void:
 		if p_pane_index < 0 or p_pane_index >= grid_line_config_per_pane.size():
 			return
@@ -406,6 +433,24 @@ class XYState extends RefCounted:
 		return scatter_style_ref_per_pane[p_pane_index] != p_style_ref
 
 
+	func save_line_style_for_pane(p_pane_index: int, p_style: TauLineStyle) -> void:
+		if p_pane_index < 0 or p_pane_index >= line_style_per_pane.size():
+			return
+		line_style_per_pane[p_pane_index] = p_style.duplicate() if p_style != null else null
+
+
+	func save_line_style_ref_for_pane(p_pane_index: int, p_style_ref: TauLineStyle) -> void:
+		if p_pane_index < 0 or p_pane_index >= line_style_ref_per_pane.size():
+			return
+		line_style_ref_per_pane[p_pane_index] = p_style_ref
+
+
+	func has_line_style_ref_changed_for_pane(p_pane_index: int, p_style_ref: TauLineStyle) -> bool:
+		if p_pane_index < 0 or p_pane_index >= line_style_ref_per_pane.size():
+			return true
+		return line_style_ref_per_pane[p_pane_index] != p_style_ref
+
+
 	func save_pane_style_for_pane(p_pane_index: int, p_style: TauPaneStyle) -> void:
 		if p_pane_index < 0 or p_pane_index >= pane_style_per_pane.size():
 			return

From e884e4cf7ba510562097fb170eb7c54e88e12967 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Fri, 24 Apr 2026 12:33:12 +0200
Subject: [PATCH 03/23] Add tests

---
 .../line/linear_scale/test_line_linear.gd     | 172 +++++++
 .../line/linear_scale/test_line_linear.gd.uid |   1 +
 .../line/linear_scale/test_line_linear.tscn   |  55 +++
 .../tests/line/log_scale/test_line_log.gd     | 421 ++++++++++++++++++
 .../tests/line/log_scale/test_line_log.gd.uid |   1 +
 .../tests/line/log_scale/test_line_log.tscn   |  92 ++++
 .../line/nan_or_inf/test_line_nan_inf_skip.gd | 206 +++++++++
 .../nan_or_inf/test_line_nan_inf_skip.gd.uid  |   1 +
 .../nan_or_inf/test_line_nan_inf_skip.tscn    |  65 +++
 9 files changed, 1014 insertions(+)
 create mode 100644 addons/tau-plot/tests/line/linear_scale/test_line_linear.gd
 create mode 100644 addons/tau-plot/tests/line/linear_scale/test_line_linear.gd.uid
 create mode 100644 addons/tau-plot/tests/line/linear_scale/test_line_linear.tscn
 create mode 100644 addons/tau-plot/tests/line/log_scale/test_line_log.gd
 create mode 100644 addons/tau-plot/tests/line/log_scale/test_line_log.gd.uid
 create mode 100644 addons/tau-plot/tests/line/log_scale/test_line_log.tscn
 create mode 100644 addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd
 create mode 100644 addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd.uid
 create mode 100644 addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn

diff --git a/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd b/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd
new file mode 100644
index 0000000..3acfa70
--- /dev/null
+++ b/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd
@@ -0,0 +1,172 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
+	var y_a := PackedFloat64Array([5.0, 10.0, 8.0, 12.0])
+	var y_b := PackedFloat64Array([25.0, 28.0, 23.0, 7.0])
+	var y_c := PackedFloat64Array([30.0, 28.0, 39.0, 67.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot1.title = "SHARED_X + CONTINUOUS"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x_a := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
+	var x_b := PackedFloat64Array([9.0, 10.3, 12.7, 14.1])
+	var x_c := PackedFloat64Array([9.2, 10.1, 10.5, 10.9])
+
+	var y_a := PackedFloat64Array([5.0, 10.0, 8.0, 12.0])
+	var y_b := PackedFloat64Array([25.0, 28.0, 23.0, 7.0])
+	var y_c := PackedFloat64Array([30.0, 28.0, 39.0, 67.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b, x_c], [y_a, y_b, y_c])
+
+	%TestPlot2.title = "PER_SERIES_X + CONTINUOUS"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four"])
+	var y_a := PackedFloat64Array([5.0, 10.0, 8.0, 12.0])
+	var y_b := PackedFloat64Array([25.0, 28.0, 23.0, 7.0])
+	var y_c := PackedFloat64Array([30.0, 28.0, 39.0, 67.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot3.title = "SHARED_X + CATEGORICAL"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot3.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd.uid b/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd.uid
new file mode 100644
index 0000000..046a12b
--- /dev/null
+++ b/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd.uid
@@ -0,0 +1 @@
+uid://d0b7xei1hadvi
diff --git a/addons/tau-plot/tests/line/linear_scale/test_line_linear.tscn b/addons/tau-plot/tests/line/linear_scale/test_line_linear.tscn
new file mode 100644
index 0000000..02a14f9
--- /dev/null
+++ b/addons/tau-plot/tests/line/linear_scale/test_line_linear.tscn
@@ -0,0 +1,55 @@
+[gd_scene load_steps=3 format=3 uid="uid://bymhr4sv6e8pv"]
+
+[ext_resource type="Script" uid="uid://d0b7xei1hadvi" path="res://addons/tau-plot/tests/line/linear_scale/test_line_linear.gd" id="1_7re6l"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_67aov"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_7re6l")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Linear scale feature"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_67aov")
+title = "SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_67aov")
+title = "PER_SERIES_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_67aov")
+title = "SHARED_X + CATEGORICAL"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/log_scale/test_line_log.gd b/addons/tau-plot/tests/line/log_scale/test_line_log.gd
new file mode 100644
index 0000000..975b50b
--- /dev/null
+++ b/addons/tau-plot/tests/line/log_scale/test_line_log.gd
@@ -0,0 +1,421 @@
+@tool
+extends Control
+
+var _timer: Timer = null
+var _t: float = 0.0
+
+var _datasets: Array[TauPlot.Dataset] = []
+var _state: Array[Dictionary] = []
+
+func _ready() -> void:
+	_create_timer()
+	_setup_all_tests()
+	_timer.start()
+
+
+func _create_timer() -> void:
+	_timer = Timer.new()
+	_timer.one_shot = false
+	_timer.wait_time = 0.016
+	_timer.timeout.connect(_on_tick)
+	add_child(_timer)
+
+
+func _setup_all_tests() -> void:
+	_datasets.clear()
+	_state.clear()
+
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+
+
+func _on_tick() -> void:
+	_t += _timer.wait_time
+
+	_step_test_1()
+	_step_test_2()
+	_step_test_3()
+	_step_test_4()
+	_step_test_5()
+	_step_test_6()
+	_step_test_7()
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x_a := PackedFloat64Array([0.1, 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 500.0, 1000.0])
+	var x_b := PackedFloat64Array([0.1, 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 500.0, 1000.0].map(func (x) -> float: return 1.1*x))
+	var x_c := PackedFloat64Array([0.1, 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 500.0, 1000.0].map(func (x) -> float: return 1.2*x))
+
+	var y_a := PackedFloat64Array()
+	var y_b := PackedFloat64Array()
+	var y_c := PackedFloat64Array()
+	y_a.resize(x_a.size())
+	y_b.resize(x_b.size())
+	y_c.resize(x_c.size())
+
+	for i in range(x_a.size()):
+		y_a[i] = 5.0 +  2.5 * sin(float(i) * 0.3)
+	for i in range(x_b.size()):
+		y_b[i] = 4.0 +  2.0 * cos(float(i) * 0.5)
+	for i in range(x_c.size()):
+		y_c[i] = 3.0 +  2.5 * sin(float(i) * 0.7)
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b, x_c], [y_a, y_b, y_c])
+	_datasets.append(dataset)
+	_state.append({})
+
+	%TestPlot1.title = "[LOG X, LINEAR Y] Independent - Animated Y values in [2.5, 7.5]"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.title = "X (log scale)"
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.title = "Y (linear)"
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.range_override_enabled = true
+	y_axis.min_override = 0.01
+	y_axis.max_override = 8.00
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+
+func _step_test_1() -> void:
+	var dataset := _datasets[0]
+
+	dataset.begin_batch()
+	var ids := dataset.get_series_ids()
+	for s_i in range(ids.size()):
+		var series_id := ids[s_i]
+		var n := dataset.get_series_sample_count(series_id)
+
+		var values := PackedFloat64Array()
+		values.resize(n)
+		var phase := float(s_i) * 0.7
+		for i in range(values.size()):
+			values[i] = 5.0 + 2.5 * sin(_t + phase + float(i) * 0.5)
+
+		dataset.set_series_y_slice(series_id, 0, values)
+	dataset.end_batch()
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x_a := PackedFloat64Array([1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0])
+	var x_b := PackedFloat64Array([1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0].map(func (x) -> float: return 1.1*x))
+
+	var y_a := PackedFloat64Array()
+	var y_b := PackedFloat64Array()
+	y_a.resize(x_a.size())
+	y_b.resize(x_b.size())
+
+	for i in range(x_a.size()):
+		y_a[i] = 0.1 * pow(10.0, float(i) * 0.4)
+	for i in range(x_b.size()):
+		y_b[i] = 0.05 * pow(10.0, float(i) * 0.4)
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+	_datasets.append(dataset)
+	_state.append({})
+
+	%TestPlot2.title = "[LINEAR X, LOG Y] Independent - Animated Y values (exponential growth)"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.title = "X (linear)"
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.title = "Y (log scale)"
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	y_axis.include_zero_in_domain = false
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+
+func _step_test_2() -> void:
+	var dataset := _datasets[1]
+
+	dataset.begin_batch()
+	var ids := dataset.get_series_ids()
+	for s_i in range(ids.size()):
+		var series_id := ids[s_i]
+		var n := dataset.get_series_sample_count(series_id)
+
+		var values := PackedFloat64Array()
+		values.resize(n)
+		var base_multiplier := 0.1 if s_i == 0 else 0.05
+		var phase := float(s_i) * 1.2
+
+		for i in range(n):
+			var osc := 1.0 + 0.5 * sin(_t + phase)
+			values[i] = base_multiplier * pow(10.0, float(i) * 0.4) * osc
+
+		dataset.set_series_y_slice(series_id, 0, values)
+	dataset.end_batch()
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x_a := PackedFloat64Array([0.05, 0.1, 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 500.0, 1000.0])
+	var x_b := PackedFloat64Array([0.05, 0.1, 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 500.0, 1000.0].map(func (x) -> float: return 1.1*x))
+
+	var y_a := PackedFloat64Array()
+	var y_b := PackedFloat64Array()
+	y_a.resize(x_a.size())
+	y_b.resize(x_b.size())
+
+	for i in range(x_a.size()):
+		y_a[i] = pow(x_a[i], 0.5)
+	for i in range(x_b.size()):
+		y_b[i] = pow(x_b[i], 0.25)
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+	_datasets.append(dataset)
+	_state.append({})
+
+	%TestPlot3.title = "[LOG X, LOG Y] Independent - Animated Y values (power laws => linear in log-log)"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.title = "X (log scale)"
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.title = "Y (log scale)"
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	y_axis.include_zero_in_domain = false
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot3.plot_xy(dataset, config, bindings)
+
+
+func _step_test_3() -> void:
+	var dataset := _datasets[2]
+
+	# Animate by varying the power law exponent slightly
+	dataset.begin_batch()
+	var ids := dataset.get_series_ids()
+	for s_i in range(ids.size()):
+		var series_id := ids[s_i]
+
+		var n := dataset.get_series_sample_count(series_id)
+		var values := PackedFloat64Array()
+		values.resize(n)
+		var base_exponent := 2.0 if s_i == 0 else 1.5
+		var exponent := base_exponent + 0.3 * sin(_t + float(s_i))
+
+		for i in range(n):
+			var x_val := float(dataset.get_series_x(series_id, i))
+			values[i] = pow(x_val, exponent)
+
+		dataset.set_series_y_slice(series_id, 0, values)
+	dataset.end_batch()
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	_datasets.append(null)
+	_state.append({})
+
+
+func _step_test_4() -> void:
+	pass
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	_datasets.append(null)
+	_state.append({})
+
+
+func _step_test_5() -> void:
+	pass
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	_datasets.append(null)
+	_state.append({})
+
+
+func _step_test_6() -> void:
+	pass
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	var series_names := PackedStringArray(["Stream A", "Stream B"])
+	# Start with a few initial points
+	var x := PackedFloat64Array([1.0, 2.0, 5.0])
+
+	var y_a := PackedFloat64Array([3.0, 5.0, 4.0])
+	var y_b := PackedFloat64Array([2.0, 4.0, 3.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b], 64)
+	_datasets.append(dataset)
+	_state.append({
+		"next_x": 10.0,
+		"time_since_append_s": 0.0,
+		"append_period_s": 0.5,
+	})
+
+	%TestPlot7.title = "[LOG X] Streaming - New samples every 0.5s"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.title = "X (log scale, growing)"
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.title = "Y (linear)"
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot7.plot_xy(dataset, config, bindings)
+
+
+func _step_test_7() -> void:
+	var dataset := _datasets[6]
+	var st := _state[6]
+
+	st["time_since_append_s"] = float(st["time_since_append_s"]) + _timer.wait_time
+	if float(st["time_since_append_s"]) < float(st["append_period_s"]):
+		return
+	st["time_since_append_s"] = 0.0
+
+	var next_x := float(st["next_x"])
+
+	# Append new sample at increasing X (logarithmic progression)
+	var ys := PackedFloat64Array([
+		4.0 + 2.0 * sin(_t),
+		3.0 + 2.0 * cos(_t * 1.5)
+	])
+
+	dataset.append_shared_sample(next_x, ys)
+
+	# Next X grows exponentially (log-uniform spacing)
+	st["next_x"] = next_x * 1.5
diff --git a/addons/tau-plot/tests/line/log_scale/test_line_log.gd.uid b/addons/tau-plot/tests/line/log_scale/test_line_log.gd.uid
new file mode 100644
index 0000000..6bb7d0e
--- /dev/null
+++ b/addons/tau-plot/tests/line/log_scale/test_line_log.gd.uid
@@ -0,0 +1 @@
+uid://b5nqjwb6flndn
diff --git a/addons/tau-plot/tests/line/log_scale/test_line_log.tscn b/addons/tau-plot/tests/line/log_scale/test_line_log.tscn
new file mode 100644
index 0000000..30b6738
--- /dev/null
+++ b/addons/tau-plot/tests/line/log_scale/test_line_log.tscn
@@ -0,0 +1,92 @@
+[gd_scene load_steps=3 format=3 uid="uid://rct3vbvdtmly"]
+
+[ext_resource type="Script" uid="uid://b5nqjwb6flndn" path="res://addons/tau-plot/tests/line/log_scale/test_line_log.gd" id="1_k4moc"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_erpj8"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_k4moc")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Logarithmic scale feature"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_erpj8")
+title = "[LOG X, LINEAR Y] Independent - Animated Y values in [2.5, 7.5]"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_erpj8")
+title = "[LINEAR X, LOG Y] Independent - Animated Y values (exponential growth)"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_erpj8")
+title = "[LOG X, LOG Y] Independent - Animated Y values (power laws => linear in log-log)"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_erpj8")
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_erpj8")
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_erpj8")
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_erpj8")
+title = "[LOG X] Streaming - New samples every 0.5s"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd
new file mode 100644
index 0000000..4258a41
--- /dev/null
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd
@@ -0,0 +1,206 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x := PackedFloat64Array([0.0, NAN, 1.0, INF, 2.0, 2.5])
+	var y_a := PackedFloat64Array([1.0, 2.0, 1.4, 2.2, 1.1, 1.8])
+	var y_b := PackedFloat64Array([1.5, 1.0, 1.6, 2.4, 0.5, 1.2])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	%TestPlot1.title = "[SHARED_X] 2nd and 4th x values are invalid"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+
+	var pane_config := TauPaneConfig.new()
+	pane_config.y_left_axis = y_axis
+	pane_config.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane_config]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x_a := PackedFloat64Array([0.0, NAN, 1.0, INF, 2.0, 2.5])
+	var x_b := PackedFloat64Array([0.25, 0.75, 1.25, 1.75, 2.25])
+	var y_a := PackedFloat64Array([1.0, 2.0, 1.4, 2.2, 1.1, 1.8])
+	var y_b := PackedFloat64Array([1.5, 1.0, 1.6, 2.4, 0.5])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	%TestPlot2.title = "[PER_SERIES_X] 2nd and 4th x values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_3() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5])
+	var y_a := PackedFloat64Array([1.0, NAN, 1.4, INF, 1.1, 1.8])
+	var y_b := PackedFloat64Array([1.5, 1.0, 1.6, 2.4, 0.5, 1.2])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	%TestPlot3.title = "[SHARED_X] 2nd and 4th y values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+
+	var pane_config := TauPaneConfig.new()
+	pane_config.y_left_axis = y_axis
+	pane_config.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane_config]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot3.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x_a := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5])
+	var x_b := PackedFloat64Array([0.25, 0.75, 1.25, 1.75, 2.25])
+	var y_a := PackedFloat64Array([1.0, NAN, 1.4, INF, 1.1, 1.8])
+	var y_b := PackedFloat64Array([1.5, 1.0, 1.6, 2.4, 0.5])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	%TestPlot4.title = "[PER_SERIES_X] 2nd and 4th y values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot4.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd.uid b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd.uid
new file mode 100644
index 0000000..92658b8
--- /dev/null
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd.uid
@@ -0,0 +1 @@
+uid://bokuk27l1c8du
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn
new file mode 100644
index 0000000..5759e00
--- /dev/null
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn
@@ -0,0 +1,65 @@
+[gd_scene load_steps=3 format=3 uid="uid://cx0yem6x7nexc"]
+
+[ext_resource type="Script" uid="uid://bokuk27l1c8du" path="res://addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd" id="1_e73yd"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_5c7d4"]
+
+[node name="Scatters" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_e73yd")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test nan and inf values with GapPolicy.SKIP"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 2
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_5c7d4")
+title = "[SHARED_X] 2nd and 4th x values are invalid"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_5c7d4")
+title = "[PER_SERIES_X] 2nd and 4th x values are invalid for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_5c7d4")
+title = "[SHARED_X] 2nd and 4th y values are invalid for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_5c7d4")
+title = "[PER_SERIES_X] 2nd and 4th y values are invalid for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"

From 1025c0cbaaf64b994a1cf0a7c02e0581d5d53da4 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Sat, 25 Apr 2026 11:42:37 +0200
Subject: [PATCH 04/23] Implement GapPolicy

---
 addons/tau-plot/plot/xy/line/line_config.gd   |  21 +
 addons/tau-plot/plot/xy/line/line_renderer.gd |  28 +-
 ...t_line_log.gd => test_line_logarithmic.gd} |   0
 ...og.gd.uid => test_line_logarithmic.gd.uid} |   0
 ...ne_log.tscn => test_line_logarithmic.tscn} |   2 +-
 .../nan_or_inf/test_line_nan_inf_bridge.gd    | 416 ++++++++++++++++++
 .../test_line_nan_inf_bridge.gd.uid           |   1 +
 .../nan_or_inf/test_line_nan_inf_bridge.tscn  | 105 +++++
 .../line/nan_or_inf/test_line_nan_inf_skip.gd | 248 ++++++++++-
 .../nan_or_inf/test_line_nan_inf_skip.tscn    |  50 ++-
 10 files changed, 837 insertions(+), 34 deletions(-)
 rename addons/tau-plot/tests/line/log_scale/{test_line_log.gd => test_line_logarithmic.gd} (100%)
 rename addons/tau-plot/tests/line/log_scale/{test_line_log.gd.uid => test_line_logarithmic.gd.uid} (100%)
 rename addons/tau-plot/tests/line/log_scale/{test_line_log.tscn => test_line_logarithmic.tscn} (97%)
 create mode 100644 addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd
 create mode 100644 addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd.uid
 create mode 100644 addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.tscn

diff --git a/addons/tau-plot/plot/xy/line/line_config.gd b/addons/tau-plot/plot/xy/line/line_config.gd
index 6cfb4c8..e09bcae 100644
--- a/addons/tau-plot/plot/xy/line/line_config.gd
+++ b/addons/tau-plot/plot/xy/line/line_config.gd
@@ -23,6 +23,25 @@ enum LineMode
 const StackedNormalization = preload("res://addons/tau-plot/plot/xy/stacked_normalization.gd").StackedNormalization
 @export var stacked_normalization: StackedNormalization = StackedNormalization.NONE
 
+## Strategy applied when the curve encounters a sample with a NaN or infinite
+## X or Y value (or a value forbidden by the active axis scale, such as a
+## non-positive value on a logarithmic axis).
+##
+## SKIP breaks the polyline at the invalid sample. The runs on each side of
+## the gap are drawn as independent contiguous polylines.
+##
+## BRIDGE drops the invalid sample from the sequence and connects the valid
+## sample before it directly to the valid sample after it, so the polyline
+## stays continuous across the gap.
+##
+## This property is visual-only and does not affect layout or domain.
+enum GapPolicy
+{
+	SKIP,    ## Break the polyline at invalid samples.
+	BRIDGE   ## Drop invalid samples and connect the surrounding valid samples.
+}
+@export var gap_policy: GapPolicy = GapPolicy.SKIP
+
 ## Maximum pixel distance from the cursor to a sample position for the sample
 ## to be considered a hover hit.
 ##
@@ -69,6 +88,8 @@ func is_equal_to(p_other: TauPaneOverlayConfig) -> bool:
 		return false
 	if stacked_normalization != other.stacked_normalization:
 		return false
+	if gap_policy != other.gap_policy:
+		return false
 	if hover_max_distance_px != other.hover_max_distance_px:
 		return false
 
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index 482a347..31f1a4d 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -15,9 +15,12 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 # draw_polyline() call per series.
 #
 # Runtime behavior:
-# - NaN and Inf X or Y values break the polyline (SKIP gap policy).
-# - Logarithmic Y scales: y <= 0 breaks the polyline.
-# - Logarithmic X scales: x <= 0 breaks the polyline.
+# - NaN and Inf X or Y values are treated according to TauLineConfig.gap_policy.
+# - Logarithmic Y scales: y <= 0 is treated as invalid.
+# - Logarithmic X scales: x <= 0 is treated as invalid.
+# - GapPolicy.SKIP breaks the polyline at every invalid sample.
+# - GapPolicy.BRIDGE drops invalid samples and keeps the polyline contiguous,
+#   so the surrounding valid samples are connected directly.
 #
 # LineValidator is expected to enforce binding-level typing constraints.
 class LineRenderer extends Control:
@@ -118,11 +121,13 @@ class LineRenderer extends Control:
 			_draw_series_independent(series_index, width_px)
 
 
-	# Draws a single series as one or more polyline runs, respecting SKIP
-	# gap policy. Run emission follows these rules:
+	# Draws a single series as one or more polyline runs, respecting the
+	# active gap policy. Run emission follows these rules:
 	#   - A valid sample is appended to the current run.
 	#   - An invalid sample (NaN/Inf X or Y, or a value forbidden by the
-	#     active axis scale) flushes the current run and starts a new one.
+	#     active axis scale) is handled according to gap_policy:
+	#     - SKIP   flushes the current run and starts a new one.
+	#     - BRIDGE drops the sample and keeps appending into the same run.
 	#   - A run of fewer than two points is discarded (no polyline).
 	func _draw_series_independent(p_series_index: int, p_width_px: float) -> void:
 		var x_cfg := _get_x_axis_config()
@@ -137,6 +142,7 @@ class LineRenderer extends Control:
 		var global_series_index := _get_global_series_index(p_series_index)
 		var color := _resolve_series_color(global_series_index)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
+		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 
 		var run := PackedVector2Array()
 
@@ -146,12 +152,14 @@ class LineRenderer extends Control:
 		for i in range(sample_count):
 			var x_value: float = float(_dataset.get_shared_x(i)) if is_shared_x else float(_dataset.get_series_x(series_id, i))
 			if is_nan(x_value) or is_inf(x_value) or not _is_x_value_valid_for_scale(x_value):
-				run = _flush_run(run, color, p_width_px)
+				if not bridge:
+					run = _flush_run(run, color, p_width_px)
 				continue
 
 			var y_value := _dataset.get_series_y(series_id, i)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
-				run = _flush_run(run, color, p_width_px)
+				if not bridge:
+					run = _flush_run(run, color, p_width_px)
 				continue
 
 			var x_px := _layout.map_x_to_px(_pane_index, x_value)
@@ -167,6 +175,7 @@ class LineRenderer extends Control:
 		var global_series_index := _get_global_series_index(p_series_index)
 		var color := _resolve_series_color(global_series_index)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
+		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 
 		var run := PackedVector2Array()
 		var sample_count := _dataset.get_series_sample_count(series_id)
@@ -174,7 +183,8 @@ class LineRenderer extends Control:
 		for cat_idx in range(sample_count):
 			var y_value := _dataset.get_series_y(series_id, cat_idx)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
-				run = _flush_run(run, color, p_width_px)
+				if not bridge:
+					run = _flush_run(run, color, p_width_px)
 				continue
 
 			var x_px := _layout.map_x_category_center_to_px(_pane_index, cat_idx)
diff --git a/addons/tau-plot/tests/line/log_scale/test_line_log.gd b/addons/tau-plot/tests/line/log_scale/test_line_logarithmic.gd
similarity index 100%
rename from addons/tau-plot/tests/line/log_scale/test_line_log.gd
rename to addons/tau-plot/tests/line/log_scale/test_line_logarithmic.gd
diff --git a/addons/tau-plot/tests/line/log_scale/test_line_log.gd.uid b/addons/tau-plot/tests/line/log_scale/test_line_logarithmic.gd.uid
similarity index 100%
rename from addons/tau-plot/tests/line/log_scale/test_line_log.gd.uid
rename to addons/tau-plot/tests/line/log_scale/test_line_logarithmic.gd.uid
diff --git a/addons/tau-plot/tests/line/log_scale/test_line_log.tscn b/addons/tau-plot/tests/line/log_scale/test_line_logarithmic.tscn
similarity index 97%
rename from addons/tau-plot/tests/line/log_scale/test_line_log.tscn
rename to addons/tau-plot/tests/line/log_scale/test_line_logarithmic.tscn
index 30b6738..280d768 100644
--- a/addons/tau-plot/tests/line/log_scale/test_line_log.tscn
+++ b/addons/tau-plot/tests/line/log_scale/test_line_logarithmic.tscn
@@ -1,6 +1,6 @@
 [gd_scene load_steps=3 format=3 uid="uid://rct3vbvdtmly"]
 
-[ext_resource type="Script" uid="uid://b5nqjwb6flndn" path="res://addons/tau-plot/tests/line/log_scale/test_line_log.gd" id="1_k4moc"]
+[ext_resource type="Script" uid="uid://b5nqjwb6flndn" path="res://addons/tau-plot/tests/line/log_scale/test_line_logarithmic.gd" id="1_k4moc"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_erpj8"]
 
 [node name="Bars" type="VBoxContainer"]
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd
new file mode 100644
index 0000000..ca687e2
--- /dev/null
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd
@@ -0,0 +1,416 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x := PackedFloat64Array([0.0, 0.5, NAN, INF, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([1.0, 2.0, 4.0, 4.5, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	%TestPlot1.title = "[SHARED_X] 3rd and 4th x values are invalid"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+
+	var pane_config := TauPaneConfig.new()
+	pane_config.y_left_axis = y_axis
+	pane_config.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane_config]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x_a := PackedFloat64Array([0.0, 0.5, NAN, INF, 2.0, 2.5, 3.0])
+	var x_b := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([1.0, 2.0, 4.0, 4.5, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	%TestPlot2.title = "[PER_SERIES_X] 3rd and 4th x values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([1.0, 2.0, INF, NAN, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	%TestPlot3.title = "[SHARED_X] 3rd and 4th y values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+
+	var pane_config := TauPaneConfig.new()
+	pane_config.y_left_axis = y_axis
+	pane_config.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane_config]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot3.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x_a := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var x_b := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([1.0, 2.0, INF, NAN, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	%TestPlot4.title = "[PER_SERIES_X] 3rd and 4th y values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot4.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x := PackedFloat64Array([pow(10, -3), pow(10, -2), -pow(10, -1), NAN, pow(10, 1), pow(10, 2), pow(10, 3)])
+	var y_a := PackedFloat64Array([1.0, 2.0, 4.0, 4.5, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	%TestPlot5.title = "[LOG][SHARED_X] 3rd and 4th x values are invalid"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+
+	var pane_config := TauPaneConfig.new()
+	pane_config.y_left_axis = y_axis
+	pane_config.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane_config]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot5.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x_a := PackedFloat64Array([pow(10, -3), pow(10, -2), -pow(10, -1), INF, pow(10, 1), pow(10, 2), pow(10, 3)])
+	var x_b := PackedFloat64Array([pow(10, -3), pow(10, -2), pow(10, -1), pow(10, 0), pow(10, 1), pow(10, 2), pow(10, 3)])
+	var y_a := PackedFloat64Array([1.0, 2.0, 4.0, 4.5, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	%TestPlot6.title = "[LOG][PER_SERIES_X] 3rd and 4th x values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot6.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([pow(10, 1), pow(10, 2), -pow(10, 4), INF,        pow(10, 4), pow(10, 2), pow(10, 1)])
+	var y_b := PackedFloat64Array([pow(10, 2), pow(10, 3),  pow(10, 5), pow(10, 6), pow(10, 5), pow(10, 3), pow(10, 2)])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	%TestPlot7.title = "[LOG][SHARED_X] 3rd and 4th y values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	y_axis.include_zero_in_domain = false
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+
+	var pane_config := TauPaneConfig.new()
+	pane_config.y_left_axis = y_axis
+	pane_config.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane_config]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot7.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x_a := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var x_b := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([pow(10, 1), pow(10, 2), -pow(10, 4), INF,        pow(10, 4), pow(10, 2), pow(10, 1)])
+	var y_b := PackedFloat64Array([pow(10, 2), pow(10, 3),  pow(10, 5), pow(10, 6), pow(10, 5), pow(10, 3), pow(10, 2)])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	%TestPlot8.title = "[LOG][PER_SERIES_X] 3rd and 4th y values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	y_axis.include_zero_in_domain = false
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot8.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd.uid b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd.uid
new file mode 100644
index 0000000..e9e4af0
--- /dev/null
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd.uid
@@ -0,0 +1 @@
+uid://cym0c8dl4swxu
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.tscn b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.tscn
new file mode 100644
index 0000000..bc0c825
--- /dev/null
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.tscn
@@ -0,0 +1,105 @@
+[gd_scene load_steps=3 format=3 uid="uid://d0icnobe65vpy"]
+
+[ext_resource type="Script" uid="uid://cym0c8dl4swxu" path="res://addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd" id="1_156gm"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_v7edd"]
+
+[node name="Scatters" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_156gm")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test invalid values with GapPolicy.BRIDGE"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 2
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_v7edd")
+title = "[SHARED_X] 2nd and 4th x values are invalid"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_v7edd")
+title = "[PER_SERIES_X] 2nd and 4th x values are invalid for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_v7edd")
+title = "[SHARED_X] 2nd and 4th y values are invalid for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_v7edd")
+title = "[PER_SERIES_X] 2nd and 4th y values are invalid for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_v7edd")
+title = "[LOG][SHARED_X] 2nd and 4th x values are negative"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_v7edd")
+title = "[LOG][PER_SERIES_X] 2nd and 4th x values are negative for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_v7edd")
+title = "[LOG][SHARED_X] 2nd and 4th y values are negative for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_v7edd")
+title = "[LOG][PER_SERIES_X] 2nd and 4th y values are negative for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd
index 4258a41..1537c8a 100644
--- a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd
@@ -6,6 +6,10 @@ func _ready() -> void:
 	_setup_test_2()
 	_setup_test_3()
 	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
 
 ####################################################################################################
 # Test 1
@@ -13,13 +17,13 @@ func _ready() -> void:
 
 func _setup_test_1() -> void:
 	var series_names := PackedStringArray(["A", "B"])
-	var x := PackedFloat64Array([0.0, NAN, 1.0, INF, 2.0, 2.5])
-	var y_a := PackedFloat64Array([1.0, 2.0, 1.4, 2.2, 1.1, 1.8])
-	var y_b := PackedFloat64Array([1.5, 1.0, 1.6, 2.4, 0.5, 1.2])
+	var x := PackedFloat64Array([0.0, 0.5, NAN, INF, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([1.0, 2.0, 4.0, 4.5, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
 
 	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
 
-	%TestPlot1.title = "[SHARED_X] 2nd and 4th x values are invalid"
+	%TestPlot1.title = "[SHARED_X] 3rd and 4th x values are invalid"
 
 	var x_axis := TauAxisConfig.new()
 	x_axis.type = TauAxisConfig.Type.CONTINUOUS
@@ -32,6 +36,7 @@ func _setup_test_1() -> void:
 	y_axis.include_zero_in_domain = true
 
 	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -62,14 +67,14 @@ func _setup_test_1() -> void:
 
 func _setup_test_2() -> void:
 	var series_names := PackedStringArray(["A", "B"])
-	var x_a := PackedFloat64Array([0.0, NAN, 1.0, INF, 2.0, 2.5])
-	var x_b := PackedFloat64Array([0.25, 0.75, 1.25, 1.75, 2.25])
-	var y_a := PackedFloat64Array([1.0, 2.0, 1.4, 2.2, 1.1, 1.8])
-	var y_b := PackedFloat64Array([1.5, 1.0, 1.6, 2.4, 0.5])
+	var x_a := PackedFloat64Array([0.0, 0.5, NAN, INF, 2.0, 2.5, 3.0])
+	var x_b := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([1.0, 2.0, 4.0, 4.5, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
 
 	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
 
-	%TestPlot2.title = "[PER_SERIES_X] 2nd and 4th x values are invalid for series A"
+	%TestPlot2.title = "[PER_SERIES_X] 3rd and 4th x values are invalid for series A"
 
 	var x_axis := TauAxisConfig.new()
 	x_axis.type = TauAxisConfig.Type.CONTINUOUS
@@ -82,6 +87,7 @@ func _setup_test_2() -> void:
 	y_axis.include_zero_in_domain = true
 
 	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -107,18 +113,18 @@ func _setup_test_2() -> void:
 	%TestPlot2.plot_xy(dataset, config, bindings)
 
 ####################################################################################################
-# Test 5
+# Test 3
 ####################################################################################################
 
 func _setup_test_3() -> void:
 	var series_names := PackedStringArray(["A", "B"])
-	var x := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5])
-	var y_a := PackedFloat64Array([1.0, NAN, 1.4, INF, 1.1, 1.8])
-	var y_b := PackedFloat64Array([1.5, 1.0, 1.6, 2.4, 0.5, 1.2])
+	var x := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([1.0, 2.0, INF, NAN, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
 
 	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
 
-	%TestPlot3.title = "[SHARED_X] 2nd and 4th y values are invalid for series A"
+	%TestPlot3.title = "[SHARED_X] 3rd and 4th y values are invalid for series A"
 
 	var x_axis := TauAxisConfig.new()
 	x_axis.type = TauAxisConfig.Type.CONTINUOUS
@@ -131,6 +137,7 @@ func _setup_test_3() -> void:
 	y_axis.include_zero_in_domain = true
 
 	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -161,14 +168,14 @@ func _setup_test_3() -> void:
 
 func _setup_test_4() -> void:
 	var series_names := PackedStringArray(["A", "B"])
-	var x_a := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5])
-	var x_b := PackedFloat64Array([0.25, 0.75, 1.25, 1.75, 2.25])
-	var y_a := PackedFloat64Array([1.0, NAN, 1.4, INF, 1.1, 1.8])
-	var y_b := PackedFloat64Array([1.5, 1.0, 1.6, 2.4, 0.5])
+	var x_a := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var x_b := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([1.0, 2.0, INF, NAN, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
 
 	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
 
-	%TestPlot4.title = "[PER_SERIES_X] 2nd and 4th y values are invalid for series A"
+	%TestPlot4.title = "[PER_SERIES_X] 3rd and 4th y values are invalid for series A"
 
 	var x_axis := TauAxisConfig.new()
 	x_axis.type = TauAxisConfig.Type.CONTINUOUS
@@ -181,6 +188,7 @@ func _setup_test_4() -> void:
 	y_axis.include_zero_in_domain = true
 
 	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -204,3 +212,205 @@ func _setup_test_4() -> void:
 	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
 
 	%TestPlot4.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x := PackedFloat64Array([pow(10, -3), pow(10, -2), -pow(10, -1), NAN, pow(10, 1), pow(10, 2), pow(10, 3)])
+	var y_a := PackedFloat64Array([1.0, 2.0, 4.0, 4.5, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	%TestPlot5.title = "[LOG][SHARED_X] 3rd and 4th x values are invalid"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+
+	var pane_config := TauPaneConfig.new()
+	pane_config.y_left_axis = y_axis
+	pane_config.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane_config]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot5.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x_a := PackedFloat64Array([pow(10, -3), pow(10, -2), -pow(10, -1), INF, pow(10, 1), pow(10, 2), pow(10, 3)])
+	var x_b := PackedFloat64Array([pow(10, -3), pow(10, -2), pow(10, -1), pow(10, 0), pow(10, 1), pow(10, 2), pow(10, 3)])
+	var y_a := PackedFloat64Array([1.0, 2.0, 4.0, 4.5, 4.0, 2.0, 1.0])
+	var y_b := PackedFloat64Array([2.0, 3.0, 5.0, 5.5, 5.0, 3.0, 2.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	%TestPlot6.title = "[LOG][PER_SERIES_X] 3rd and 4th x values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.include_zero_in_domain = true
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot6.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([pow(10, 1), pow(10, 2), -pow(10, 4), INF,        pow(10, 4), pow(10, 2), pow(10, 1)])
+	var y_b := PackedFloat64Array([pow(10, 2), pow(10, 3),  pow(10, 5), pow(10, 6), pow(10, 5), pow(10, 3), pow(10, 2)])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	%TestPlot7.title = "[LOG][SHARED_X] 3rd and 4th y values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	y_axis.include_zero_in_domain = false
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+
+	var pane_config := TauPaneConfig.new()
+	pane_config.y_left_axis = y_axis
+	pane_config.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane_config]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot7.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	var series_names := PackedStringArray(["A", "B"])
+	var x_a := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var x_b := PackedFloat64Array([0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0])
+	var y_a := PackedFloat64Array([pow(10, 1), pow(10, 2), -pow(10, 4), INF,        pow(10, 4), pow(10, 2), pow(10, 1)])
+	var y_b := PackedFloat64Array([pow(10, 2), pow(10, 3),  pow(10, 5), pow(10, 6), pow(10, 5), pow(10, 3), pow(10, 2)])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	%TestPlot8.title = "[LOG][PER_SERIES_X] 3rd and 4th y values are invalid for series A"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 8
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	y_axis.include_zero_in_domain = false
+
+	var line_config := TauLineConfig.new()
+	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+	config.style.series_alpha = 0.8
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	%TestPlot8.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn
index 5759e00..9e7f315 100644
--- a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn
@@ -14,7 +14,7 @@ script = ExtResource("1_e73yd")
 [node name="Title" type="Label" parent="."]
 layout_mode = 2
 theme_override_font_sizes/font_size = 32
-text = "Test nan and inf values with GapPolicy.SKIP"
+text = "Test invalid values with GapPolicy.SKIP"
 horizontal_alignment = 1
 
 [node name="GridContainer" type="GridContainer" parent="."]
@@ -31,7 +31,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_5c7d4")
-title = "[SHARED_X] 2nd and 4th x values are invalid"
+title = "[SHARED_X] 3rd and 4th x values are invalid"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
@@ -41,7 +41,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_5c7d4")
-title = "[PER_SERIES_X] 2nd and 4th x values are invalid for series A"
+title = "[PER_SERIES_X] 3rd and 4th x values are invalid for series A"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
@@ -51,7 +51,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_5c7d4")
-title = "[SHARED_X] 2nd and 4th y values are invalid for series A"
+title = "[SHARED_X] 3rd and 4th y values are invalid for series A"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
@@ -61,5 +61,45 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_5c7d4")
-title = "[PER_SERIES_X] 2nd and 4th y values are invalid for series A"
+title = "[PER_SERIES_X] 3rd and 4th y values are invalid for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_5c7d4")
+title = "[LOG][SHARED_X] 3rd and 4th x values are invalid"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_5c7d4")
+title = "[LOG][PER_SERIES_X] 3rd and 4th x values are invalid for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_5c7d4")
+title = "[LOG][SHARED_X] 3rd and 4th y values are invalid for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_5c7d4")
+title = "[LOG][PER_SERIES_X] 3rd and 4th y values are invalid for series A"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"

From 6a0481e443083f022cfeb614f0278633714c101a Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Sun, 26 Apr 2026 13:56:56 +0200
Subject: [PATCH 05/23] Implement STEP_BEFORE, STEP_AFTER and STEP_MIDDLE

---
 addons/tau-plot/plot/xy/line/line_config.gd   |  23 ++
 addons/tau-plot/plot/xy/line/line_renderer.gd |  28 ++-
 .../test_line_interpolation_linear.gd         | 228 ++++++++++++++++++
 .../test_line_interpolation_linear.gd.uid     |   1 +
 .../test_line_interpolation_linear.tscn       | 157 ++++++++++++
 .../test_line_interpolation_logarithmic.gd    | 157 ++++++++++++
 ...test_line_interpolation_logarithmic.gd.uid |   1 +
 .../test_line_interpolation_logarithmic.tscn  | 113 +++++++++
 .../line/linear_scale/test_line_linear.gd     | 172 -------------
 .../line/linear_scale/test_line_linear.gd.uid |   1 -
 .../line/linear_scale/test_line_linear.tscn   |  55 -----
 11 files changed, 706 insertions(+), 230 deletions(-)
 create mode 100644 addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd
 create mode 100644 addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd.uid
 create mode 100644 addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn
 create mode 100644 addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd
 create mode 100644 addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd.uid
 create mode 100644 addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
 delete mode 100644 addons/tau-plot/tests/line/linear_scale/test_line_linear.gd
 delete mode 100644 addons/tau-plot/tests/line/linear_scale/test_line_linear.gd.uid
 delete mode 100644 addons/tau-plot/tests/line/linear_scale/test_line_linear.tscn

diff --git a/addons/tau-plot/plot/xy/line/line_config.gd b/addons/tau-plot/plot/xy/line/line_config.gd
index e09bcae..fc492d1 100644
--- a/addons/tau-plot/plot/xy/line/line_config.gd
+++ b/addons/tau-plot/plot/xy/line/line_config.gd
@@ -42,6 +42,27 @@ enum GapPolicy
 }
 @export var gap_policy: GapPolicy = GapPolicy.SKIP
 
+## How consecutive samples are interpolated.
+##
+## LINEAR draws a straight segment between consecutive samples.
+##
+## The three step modes interpolate as a staircase between consecutive
+## samples: only horizontal or vertical motion, with the modes differing by
+## when the vertical jump happens. STEP_BEFORE jumps as early as possible (at
+## the previous sample's X position), STEP_AFTER as late as possible (at the
+## next sample's X position), and STEP_MIDDLE jumps at the pixel midpoint
+## between the two X positions.
+##
+## This property is visual-only and does not affect layout or domain.
+enum InterpolationMode
+{
+	LINEAR,         ## Straight segment between consecutive samples.
+	STEP_BEFORE,    ## Vertical jump first at the previous sample's X, then horizontal.
+	STEP_AFTER,     ## Horizontal first, then vertical jump at the next sample's X.
+	STEP_MIDDLE     ## Horizontal, vertical jump at the pixel midpoint, horizontal.
+}
+@export var interpolation_mode: InterpolationMode = InterpolationMode.LINEAR
+
 ## Maximum pixel distance from the cursor to a sample position for the sample
 ## to be considered a hover hit.
 ##
@@ -90,6 +111,8 @@ func is_equal_to(p_other: TauPaneOverlayConfig) -> bool:
 		return false
 	if gap_policy != other.gap_policy:
 		return false
+	if interpolation_mode != other.interpolation_mode:
+		return false
 	if hover_max_distance_px != other.hover_max_distance_px:
 		return false
 
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index 31f1a4d..5cc2f13 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -21,6 +21,10 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 # - GapPolicy.SKIP breaks the polyline at every invalid sample.
 # - GapPolicy.BRIDGE drops invalid samples and keeps the polyline contiguous,
 #   so the surrounding valid samples are connected directly.
+# - TauLineConfig.interpolation_mode controls the curve drawn between two
+#   consecutive valid samples. The step modes (STEP_BEFORE, STEP_AFTER,
+#   STEP_MIDDLE) are realized by inserting synthetic intermediate points in
+#   screen space into the polyline. LINEAR draws straight segments.
 #
 # LineValidator is expected to enforce binding-level typing constraints.
 class LineRenderer extends Control:
@@ -143,6 +147,7 @@ class LineRenderer extends Control:
 		var color := _resolve_series_color(global_series_index)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
+		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
 
 		var run := PackedVector2Array()
 
@@ -164,7 +169,7 @@ class LineRenderer extends Control:
 
 			var x_px := _layout.map_x_to_px(_pane_index, x_value)
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
-			run.append(_layout.map_point_to_screen(x_px, y_px))
+			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
 
 		if run.size() >= 2:
 			draw_polyline(run, color, p_width_px)
@@ -176,6 +181,7 @@ class LineRenderer extends Control:
 		var color := _resolve_series_color(global_series_index)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
+		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
 
 		var run := PackedVector2Array()
 		var sample_count := _dataset.get_series_sample_count(series_id)
@@ -189,7 +195,7 @@ class LineRenderer extends Control:
 
 			var x_px := _layout.map_x_category_center_to_px(_pane_index, cat_idx)
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
-			run.append(_layout.map_point_to_screen(x_px, y_px))
+			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
 
 		if run.size() >= 2:
 			draw_polyline(run, color, p_width_px)
@@ -201,6 +207,24 @@ class LineRenderer extends Control:
 		return PackedVector2Array()
 
 
+	func _append_with_interpolation(p_run: PackedVector2Array, p_point: Vector2, p_mode: TauLineConfig.InterpolationMode) -> void:
+		if p_run.size() == 0 or p_mode == TauLineConfig.InterpolationMode.LINEAR:
+			p_run.append(p_point)
+			return
+
+		var last_pt: Vector2 = p_run[p_run.size() - 1]
+		match p_mode:
+			TauLineConfig.InterpolationMode.STEP_BEFORE:
+				p_run.append(Vector2(last_pt.x, p_point.y))
+			TauLineConfig.InterpolationMode.STEP_AFTER:
+				p_run.append(Vector2(p_point.x, last_pt.y))
+			TauLineConfig.InterpolationMode.STEP_MIDDLE:
+				var mid_x: float = (last_pt.x + p_point.x) * 0.5
+				p_run.append(Vector2(mid_x, last_pt.y))
+				p_run.append(Vector2(mid_x, p_point.y))
+		p_run.append(p_point)
+
+
 	####################################################################################################
 	# Series helpers
 	####################################################################################################
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd
new file mode 100644
index 0000000..80466dc
--- /dev/null
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd
@@ -0,0 +1,228 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+	_setup_test_9()
+	_setup_test_10()
+	_setup_test_11()
+	_setup_test_12()
+
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x_a := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a], [y_a])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+func make_shared_x_categorical_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_per_series_x_continuous_plot(%TestPlot2, "[LINEAR] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_categorical_plot(%TestPlot3, "[LINEAR] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_BEFORE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_per_series_x_continuous_plot(%TestPlot5, "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_shared_x_categorical_plot(%TestPlot6, "[STEP_BEFORE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "[STEP_MIDDLE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_per_series_x_continuous_plot(%TestPlot8, "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_categorical_plot(%TestPlot9, "[STEP_MIDDLE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 10
+####################################################################################################
+
+func _setup_test_10() -> void:
+	make_shared_x_continuous_plot(%TestPlot10, "[STEP_AFTER] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 11
+####################################################################################################
+
+func _setup_test_11() -> void:
+	make_per_series_x_continuous_plot(%TestPlot11, "[STEP_AFTER] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 12
+####################################################################################################
+
+func _setup_test_12() -> void:
+	make_shared_x_categorical_plot(%TestPlot12, "[STEP_AFTER] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_AFTER)
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd.uid b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd.uid
new file mode 100644
index 0000000..af94b4e
--- /dev/null
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd.uid
@@ -0,0 +1 @@
+uid://dagnw8rnu7ils
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn
new file mode 100644
index 0000000..57f6107
--- /dev/null
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn
@@ -0,0 +1,157 @@
+[gd_scene load_steps=3 format=3 uid="uid://dhokcl8lmbwud"]
+
+[ext_resource type="Script" uid="uid://dagnw8rnu7ils" path="res://addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd" id="1_ahkji"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_nry5o"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_ahkji")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Interpolation modes with linear scale"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[LINEAR] SHARED_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[LINEAR] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[LINEAR] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[STEP_BEFORE] SHARED_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[STEP_BEFORE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[STEP_MIDDLE] SHARED_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[STEP_MIDDLE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot10" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[STEP_AFTER] SHARED_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot11" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot12" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[STEP_AFTER] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd
new file mode 100644
index 0000000..564bc96
--- /dev/null
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd
@@ -0,0 +1,157 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([pow(10, -2), pow(10, -1), pow(10, 0), pow(10, 1), pow(10, 2)])
+	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	x_axis.include_zero_in_domain = false
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x_a := PackedFloat64Array([pow(10, -2), pow(10, -1), pow(10, 0), pow(10, 1), pow(10, 2)])
+	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a], [y_a])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	x_axis.include_zero_in_domain = false
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_per_series_x_continuous_plot(%TestPlot2, "[LINEAR] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "[STEP_BEFORE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_per_series_x_continuous_plot(%TestPlot4, "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "[STEP_MIDDLE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_per_series_x_continuous_plot(%TestPlot6, "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "[STEP_AFTER] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_per_series_x_continuous_plot(%TestPlot8, "[STEP_AFTER] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd.uid b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd.uid
new file mode 100644
index 0000000..609addc
--- /dev/null
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd.uid
@@ -0,0 +1 @@
+uid://bsivl5p06vdek
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
new file mode 100644
index 0000000..cb19e48
--- /dev/null
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
@@ -0,0 +1,113 @@
+[gd_scene load_steps=3 format=3 uid="uid://b7wpf2xypsmj2"]
+
+[ext_resource type="Script" uid="uid://bsivl5p06vdek" path="res://addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd" id="1_g1sf8"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_u5as0"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_g1sf8")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Interpolation modes with logarithmic scale"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 2
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[LINEAR] SHARED_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[LINEAR] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[STEP_BEFORE] SHARED_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[STEP_MIDDLE] SHARED_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[STEP_AFTER] SHARED_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd b/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd
deleted file mode 100644
index 3acfa70..0000000
--- a/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd
+++ /dev/null
@@ -1,172 +0,0 @@
-@tool
-extends Control
-
-func _ready() -> void:
-	_setup_test_1()
-	_setup_test_2()
-	_setup_test_3()
-
-
-####################################################################################################
-# Test 1
-####################################################################################################
-
-func _setup_test_1() -> void:
-	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
-	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
-	var y_a := PackedFloat64Array([5.0, 10.0, 8.0, 12.0])
-	var y_b := PackedFloat64Array([25.0, 28.0, 23.0, 7.0])
-	var y_c := PackedFloat64Array([30.0, 28.0, 39.0, 67.0])
-
-	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
-
-	%TestPlot1.title = "SHARED_X + CONTINUOUS"
-
-	var x_axis := TauAxisConfig.new()
-	x_axis.type = TauAxisConfig.Type.CONTINUOUS
-	x_axis.scale = TauAxisConfig.Scale.LINEAR
-
-	var y_axis := TauAxisConfig.new()
-	y_axis.type = TauAxisConfig.Type.CONTINUOUS
-	y_axis.scale = TauAxisConfig.Scale.LINEAR
-
-	var line_config := TauLineConfig.new()
-	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
-
-	var pane := TauPaneConfig.new()
-	pane.y_left_axis = y_axis
-	pane.overlays = [line_config]
-
-	var config := TauXYConfig.new()
-	config.x_axis = x_axis
-	config.panes = [pane]
-
-	var sb_a := TauXYSeriesBinding.new()
-	sb_a.series_id = dataset.get_series_id_by_index(0)
-	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
-	sb_a.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_b := TauXYSeriesBinding.new()
-	sb_b.series_id = dataset.get_series_id_by_index(1)
-	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
-	sb_b.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_c := TauXYSeriesBinding.new()
-	sb_c.series_id = dataset.get_series_id_by_index(2)
-	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
-	sb_c.y_axis_id = TauPlot.AxisId.LEFT
-
-	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
-
-	%TestPlot1.plot_xy(dataset, config, bindings)
-
-
-####################################################################################################
-# Test 2
-####################################################################################################
-
-func _setup_test_2() -> void:
-	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
-	var x_a := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
-	var x_b := PackedFloat64Array([9.0, 10.3, 12.7, 14.1])
-	var x_c := PackedFloat64Array([9.2, 10.1, 10.5, 10.9])
-
-	var y_a := PackedFloat64Array([5.0, 10.0, 8.0, 12.0])
-	var y_b := PackedFloat64Array([25.0, 28.0, 23.0, 7.0])
-	var y_c := PackedFloat64Array([30.0, 28.0, 39.0, 67.0])
-
-	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b, x_c], [y_a, y_b, y_c])
-
-	%TestPlot2.title = "PER_SERIES_X + CONTINUOUS"
-
-	var x_axis := TauAxisConfig.new()
-	x_axis.type = TauAxisConfig.Type.CONTINUOUS
-	x_axis.scale = TauAxisConfig.Scale.LINEAR
-
-	var y_axis := TauAxisConfig.new()
-	y_axis.type = TauAxisConfig.Type.CONTINUOUS
-	y_axis.scale = TauAxisConfig.Scale.LINEAR
-
-	var line_config := TauLineConfig.new()
-	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
-
-	var pane := TauPaneConfig.new()
-	pane.y_left_axis = y_axis
-	pane.overlays = [line_config]
-
-	var config := TauXYConfig.new()
-	config.x_axis = x_axis
-	config.panes = [pane]
-
-	var sb_a := TauXYSeriesBinding.new()
-	sb_a.series_id = dataset.get_series_id_by_index(0)
-	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
-	sb_a.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_b := TauXYSeriesBinding.new()
-	sb_b.series_id = dataset.get_series_id_by_index(1)
-	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
-	sb_b.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_c := TauXYSeriesBinding.new()
-	sb_c.series_id = dataset.get_series_id_by_index(2)
-	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
-	sb_c.y_axis_id = TauPlot.AxisId.LEFT
-
-	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
-
-	%TestPlot2.plot_xy(dataset, config, bindings)
-
-
-####################################################################################################
-# Test 3
-####################################################################################################
-
-func _setup_test_3() -> void:
-	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
-	var x := PackedStringArray(["One", "Two", "Three", "Four"])
-	var y_a := PackedFloat64Array([5.0, 10.0, 8.0, 12.0])
-	var y_b := PackedFloat64Array([25.0, 28.0, 23.0, 7.0])
-	var y_c := PackedFloat64Array([30.0, 28.0, 39.0, 67.0])
-
-	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
-
-	%TestPlot3.title = "SHARED_X + CATEGORICAL"
-
-	var x_axis := TauAxisConfig.new()
-	x_axis.type = TauAxisConfig.Type.CATEGORICAL
-	x_axis.scale = TauAxisConfig.Scale.LINEAR
-
-	var y_axis := TauAxisConfig.new()
-	y_axis.type = TauAxisConfig.Type.CONTINUOUS
-	y_axis.scale = TauAxisConfig.Scale.LINEAR
-
-	var line_config := TauLineConfig.new()
-	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
-
-	var pane := TauPaneConfig.new()
-	pane.y_left_axis = y_axis
-	pane.overlays = [line_config]
-
-	var config := TauXYConfig.new()
-	config.x_axis = x_axis
-	config.panes = [pane]
-
-	var sb_a := TauXYSeriesBinding.new()
-	sb_a.series_id = dataset.get_series_id_by_index(0)
-	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
-	sb_a.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_b := TauXYSeriesBinding.new()
-	sb_b.series_id = dataset.get_series_id_by_index(1)
-	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
-	sb_b.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_c := TauXYSeriesBinding.new()
-	sb_c.series_id = dataset.get_series_id_by_index(2)
-	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
-	sb_c.y_axis_id = TauPlot.AxisId.LEFT
-
-	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
-
-	%TestPlot3.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd.uid b/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd.uid
deleted file mode 100644
index 046a12b..0000000
--- a/addons/tau-plot/tests/line/linear_scale/test_line_linear.gd.uid
+++ /dev/null
@@ -1 +0,0 @@
-uid://d0b7xei1hadvi
diff --git a/addons/tau-plot/tests/line/linear_scale/test_line_linear.tscn b/addons/tau-plot/tests/line/linear_scale/test_line_linear.tscn
deleted file mode 100644
index 02a14f9..0000000
--- a/addons/tau-plot/tests/line/linear_scale/test_line_linear.tscn
+++ /dev/null
@@ -1,55 +0,0 @@
-[gd_scene load_steps=3 format=3 uid="uid://bymhr4sv6e8pv"]
-
-[ext_resource type="Script" uid="uid://d0b7xei1hadvi" path="res://addons/tau-plot/tests/line/linear_scale/test_line_linear.gd" id="1_7re6l"]
-[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_67aov"]
-
-[node name="Bars" type="VBoxContainer"]
-anchors_preset = 15
-anchor_right = 1.0
-anchor_bottom = 1.0
-grow_horizontal = 2
-grow_vertical = 2
-script = ExtResource("1_7re6l")
-
-[node name="Title" type="Label" parent="."]
-layout_mode = 2
-theme_override_font_sizes/font_size = 32
-text = "Linear scale feature"
-horizontal_alignment = 1
-
-[node name="GridContainer" type="GridContainer" parent="."]
-layout_mode = 2
-size_flags_vertical = 3
-theme_override_constants/h_separation = 0
-theme_override_constants/v_separation = 0
-columns = 3
-
-[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
-unique_name_in_owner = true
-layout_mode = 2
-size_flags_horizontal = 3
-size_flags_vertical = 3
-theme_type_variation = &"TauPlot"
-script = ExtResource("2_67aov")
-title = "SHARED_X + CONTINUOUS"
-metadata/_custom_type_script = "uid://dnhvsf2wip771"
-
-[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
-unique_name_in_owner = true
-layout_mode = 2
-size_flags_horizontal = 3
-size_flags_vertical = 3
-theme_type_variation = &"TauPlot"
-script = ExtResource("2_67aov")
-title = "PER_SERIES_X + CONTINUOUS"
-metadata/_custom_type_script = "uid://dnhvsf2wip771"
-
-[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
-unique_name_in_owner = true
-layout_mode = 2
-size_flags_horizontal = 3
-size_flags_vertical = 3
-theme_type_variation = &"TauPlot"
-script = ExtResource("2_67aov")
-title = "SHARED_X + CATEGORICAL"
-metadata/_custom_type_script = "uid://dnhvsf2wip771"

From c2f923293c92a78cd157fc76c164584cbaecaaf5 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Sun, 26 Apr 2026 15:32:47 +0200
Subject: [PATCH 06/23] Implement SMOOTH_MONOTONE

---
 addons/tau-plot/plot/xy/line/line_config.gd   |  14 +-
 addons/tau-plot/plot/xy/line/line_renderer.gd | 244 ++++++++++++++++--
 .../test_line_interpolation_linear.gd         |  34 ++-
 .../test_line_interpolation_linear.tscn       |  33 +++
 .../test_line_interpolation_logarithmic.gd    |  23 +-
 .../test_line_interpolation_logarithmic.tscn  |  22 ++
 6 files changed, 342 insertions(+), 28 deletions(-)

diff --git a/addons/tau-plot/plot/xy/line/line_config.gd b/addons/tau-plot/plot/xy/line/line_config.gd
index fc492d1..73aced2 100644
--- a/addons/tau-plot/plot/xy/line/line_config.gd
+++ b/addons/tau-plot/plot/xy/line/line_config.gd
@@ -53,13 +53,19 @@ enum GapPolicy
 ## next sample's X position), and STEP_MIDDLE jumps at the pixel midpoint
 ## between the two X positions.
 ##
+## SMOOTH_MONOTONE draws a piecewise cubic Hermite curve through the samples,
+## using Fritsch-Carlson tangent selection. The curve is C1 continuous,
+## interpolates every sample exactly, and preserves local monotonicity, so
+## no overshoot or local extrema are introduced between samples.
+##
 ## This property is visual-only and does not affect layout or domain.
 enum InterpolationMode
 {
-	LINEAR,         ## Straight segment between consecutive samples.
-	STEP_BEFORE,    ## Vertical jump first at the previous sample's X, then horizontal.
-	STEP_AFTER,     ## Horizontal first, then vertical jump at the next sample's X.
-	STEP_MIDDLE     ## Horizontal, vertical jump at the pixel midpoint, horizontal.
+	LINEAR,            ## Straight segment between consecutive samples.
+	STEP_BEFORE,       ## Vertical jump first at the previous sample's X, then horizontal.
+	STEP_AFTER,        ## Horizontal first, then vertical jump at the next sample's X.
+	STEP_MIDDLE,       ## Horizontal, vertical jump at the pixel midpoint, horizontal.
+	SMOOTH_MONOTONE    ## Fritsch-Carlson monotone piecewise cubic Hermite curve.
 }
 @export var interpolation_mode: InterpolationMode = InterpolationMode.LINEAR
 
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index 5cc2f13..361d74e 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -22,9 +22,13 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 # - GapPolicy.BRIDGE drops invalid samples and keeps the polyline contiguous,
 #   so the surrounding valid samples are connected directly.
 # - TauLineConfig.interpolation_mode controls the curve drawn between two
-#   consecutive valid samples. The step modes (STEP_BEFORE, STEP_AFTER,
-#   STEP_MIDDLE) are realized by inserting synthetic intermediate points in
-#   screen space into the polyline. LINEAR draws straight segments.
+#   consecutive valid samples. LINEAR draws straight segments. The step
+#   modes (STEP_BEFORE, STEP_AFTER, STEP_MIDDLE) insert synthetic
+#   intermediate points in screen space into the polyline. SMOOTH_MONOTONE
+#   replaces each segment with a fixed number of sub-samples from a
+#   Fritsch-Carlson piecewise cubic Hermite curve evaluated in screen space.
+#   Whichever interpolation is active, a contiguous run is still drawn with a
+#   single draw_polyline() call.
 #
 # LineValidator is expected to enforce binding-level typing constraints.
 class LineRenderer extends Control:
@@ -46,6 +50,12 @@ class LineRenderer extends Control:
 	var _line_style: TauLineStyle = null
 	var _xy_style: TauXYStyle = null
 
+	# One-shot guard for the non-monotonic SMOOTH_MONOTONE fallback warning.
+	# Reset is intentionally absent: a single warning per renderer instance
+	# is enough to surface the misconfiguration without flooding the output
+	# on every redraw.
+	var _smooth_non_monotonic_warned: bool = false
+
 
 	func _init(p_layout: XYLayout,
 				p_dataset: Dataset,
@@ -158,21 +168,22 @@ class LineRenderer extends Control:
 			var x_value: float = float(_dataset.get_shared_x(i)) if is_shared_x else float(_dataset.get_series_x(series_id, i))
 			if is_nan(x_value) or is_inf(x_value) or not _is_x_value_valid_for_scale(x_value):
 				if not bridge:
-					run = _flush_run(run, color, p_width_px)
+					_finalize_run(run, color, p_width_px, interpolation)
+					run = PackedVector2Array()
 				continue
 
 			var y_value := _dataset.get_series_y(series_id, i)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					run = _flush_run(run, color, p_width_px)
+					_finalize_run(run, color, p_width_px, interpolation)
+					run = PackedVector2Array()
 				continue
 
 			var x_px := _layout.map_x_to_px(_pane_index, x_value)
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
 			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
 
-		if run.size() >= 2:
-			draw_polyline(run, color, p_width_px)
+		_finalize_run(run, color, p_width_px, interpolation)
 
 
 	func _draw_series_categorical(p_series_index: int, p_width_px: float) -> void:
@@ -190,25 +201,22 @@ class LineRenderer extends Control:
 			var y_value := _dataset.get_series_y(series_id, cat_idx)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					run = _flush_run(run, color, p_width_px)
+					_finalize_run(run, color, p_width_px, interpolation)
+					run = PackedVector2Array()
 				continue
 
 			var x_px := _layout.map_x_category_center_to_px(_pane_index, cat_idx)
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
 			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
 
-		if run.size() >= 2:
-			draw_polyline(run, color, p_width_px)
-
-
-	func _flush_run(p_run: PackedVector2Array, p_color: Color, p_width_px: float) -> PackedVector2Array:
-		if p_run.size() >= 2:
-			draw_polyline(p_run, p_color, p_width_px)
-		return PackedVector2Array()
+		_finalize_run(run, color, p_width_px, interpolation)
 
 
 	func _append_with_interpolation(p_run: PackedVector2Array, p_point: Vector2, p_mode: TauLineConfig.InterpolationMode) -> void:
-		if p_run.size() == 0 or p_mode == TauLineConfig.InterpolationMode.LINEAR:
+		# SMOOTH_MONOTONE buffers raw sample points untouched: cubic resampling
+		# requires the full neighborhood of every sample to compute tangents and
+		# is therefore deferred to _finalize_run().
+		if p_run.size() == 0 or p_mode == TauLineConfig.InterpolationMode.LINEAR or p_mode == TauLineConfig.InterpolationMode.SMOOTH_MONOTONE:
 			p_run.append(p_point)
 			return
 
@@ -225,6 +233,208 @@ class LineRenderer extends Control:
 		p_run.append(p_point)
 
 
+	####################################################################################################
+	# Smooth-monotone (Fritsch-Carlson) resampling
+	####################################################################################################
+
+	# Number of sub-segments inserted between two consecutive samples by
+	# SMOOTH_MONOTONE. The value balances visual smoothness on a typical
+	# screen against the per-segment cost paid by draw_polyline().
+	const _SMOOTH_SUBDIVISIONS: int = 16
+
+
+	# Draw the polyline for one buffered run.
+	# For LINEAR and the step modes the buffered run is already the final polyline.
+	# For SMOOTH_MONOTONE the run is first replaced by its Fritsch-Carlson piecewise cubic resampling.
+	# Runs of fewer than two points are silently dropped.
+	func _finalize_run(p_run: PackedVector2Array, p_color: Color, p_width_px: float, p_mode: TauLineConfig.InterpolationMode) -> void:
+		var polyline: PackedVector2Array = p_run
+		if p_mode == TauLineConfig.InterpolationMode.SMOOTH_MONOTONE and p_run.size() > 2:
+			polyline = _resample_smooth_monotone(p_run)
+		if polyline.size() >= 2:
+			draw_polyline(polyline, p_color, p_width_px)
+
+
+	# Builds the Fritsch-Carlson piecewise cubic Hermite curve through p_points
+	# and returns it sampled at _SMOOTH_SUBDIVISIONS sub-segments per input
+	# segment. Operates in screen space (the input is already in pixels), which
+	# keeps the curve visually smooth regardless of axis scale.
+	#
+	# The algorithm requires strictly monotonic X. The expected case is
+	# monotonically increasing screen X, but a user-inverted X axis produces
+	# monotonically decreasing screen X. Both directions are accepted: the
+	# input is processed internally on a strictly increasing X copy and the
+	# output is reversed back when needed. Consecutive points sharing the same
+	# screen X are dropped since the secant slope is undefined at h = 0.
+	# Inputs that are not monotonic in either direction fall back to the raw
+	# polyline for that run and emit a one-shot warning.
+	func _resample_smooth_monotone(p_points: PackedVector2Array) -> PackedVector2Array:
+		var direction := _detect_monotonic_x_direction(p_points)
+		if direction == 0:
+			if not _smooth_non_monotonic_warned:
+				push_warning("LineRenderer: SMOOTH_MONOTONE received samples whose screen X is not monotonic. Falling back to a straight polyline for the affected run. Use LINEAR interpolation if your data does not have a monotonic X parameter.")
+				_smooth_non_monotonic_warned = true
+			return p_points
+
+		var ascending: bool = direction > 0
+
+		# Build strictly increasing X arrays, dropping flat-X duplicates.
+		var xs := PackedFloat32Array()
+		var ys := PackedFloat32Array()
+		var input_count := p_points.size()
+		if ascending:
+			xs.append(p_points[0].x)
+			ys.append(p_points[0].y)
+			for i in range(1, input_count):
+				if p_points[i].x > xs[xs.size() - 1]:
+					xs.append(p_points[i].x)
+					ys.append(p_points[i].y)
+		else:
+			xs.append(p_points[input_count - 1].x)
+			ys.append(p_points[input_count - 1].y)
+			for i in range(input_count - 2, -1, -1):
+				if p_points[i].x > xs[xs.size() - 1]:
+					xs.append(p_points[i].x)
+					ys.append(p_points[i].y)
+
+		var n := xs.size()
+		if n < 2:
+			# All inputs collapsed to a single screen X. Nothing to draw.
+			return PackedVector2Array()
+		if n == 2:
+			# Two distinct X values produce a straight line through Hermite
+			# with both tangents equal to the secant slope. Short-circuit.
+			var trivial := PackedVector2Array()
+			trivial.append(Vector2(xs[0], ys[0]))
+			trivial.append(Vector2(xs[1], ys[1]))
+			if not ascending:
+				trivial.reverse()
+			return trivial
+
+		var tangents := _fritsch_carlson_tangents(xs, ys)
+
+		var out := PackedVector2Array()
+		# Pre-size the output for speed: n-1 segments times subdivisions plus
+		# the very first sample.
+		out.resize(1 + (n - 1) * _SMOOTH_SUBDIVISIONS)
+		out[0] = Vector2(xs[0], ys[0])
+
+		var write_index: int = 1
+		var inv_subs: float = 1.0 / float(_SMOOTH_SUBDIVISIONS)
+		for k in range(n - 1):
+			var x0: float = xs[k]
+			var x1: float = xs[k + 1]
+			var y0: float = ys[k]
+			var y1: float = ys[k + 1]
+			var h: float = x1 - x0
+			var m0: float = tangents[k]
+			var m1: float = tangents[k + 1]
+
+			# Sub-points at t = 1/N, 2/N, ..., 1. The endpoint t=1 is the next
+			# sample, included here so the next segment begins at t=1/N.
+			for s in range(1, _SMOOTH_SUBDIVISIONS + 1):
+				var t: float = float(s) * inv_subs
+				var t2: float = t * t
+				var t3: float = t2 * t
+				var h00: float = 2.0 * t3 - 3.0 * t2 + 1.0
+				var h10: float = t3 - 2.0 * t2 + t
+				var h01: float = -2.0 * t3 + 3.0 * t2
+				var h11: float = t3 - t2
+				var x: float = x0 + t * h
+				var y: float = h00 * y0 + h10 * h * m0 + h01 * y1 + h11 * h * m1
+				out[write_index] = Vector2(x, y)
+				write_index += 1
+
+		if not ascending:
+			out.reverse()
+		return out
+
+
+	# Returns +1 if screen X is strictly monotonically increasing across the
+	# whole run, -1 if strictly decreasing, 0 if neither (some pair has equal
+	# X) or the run has fewer than 2 points. Equal consecutive X is allowed
+	# only as a single-point run (n < 2 case).
+	func _detect_monotonic_x_direction(p_points: PackedVector2Array) -> int:
+		var n := p_points.size()
+		if n < 2:
+			return 0
+		var first_diff: float = p_points[1].x - p_points[0].x
+		# Find the first non-zero diff to set the direction. Equal-X pairs in
+		# the middle of an otherwise increasing run are tolerated and dropped
+		# by the caller, so they do not invalidate monotonicity here.
+		var direction: int = 0
+		if first_diff > 0.0:
+			direction = 1
+		elif first_diff < 0.0:
+			direction = -1
+		for i in range(2, n):
+			var diff: float = p_points[i].x - p_points[i - 1].x
+			if diff > 0.0:
+				if direction == -1:
+					return 0
+				direction = 1
+			elif diff < 0.0:
+				if direction == 1:
+					return 0
+				direction = -1
+		return direction
+
+
+	# Fritsch-Carlson tangent computation. Returns one tangent per input point
+	# such that the resulting piecewise cubic Hermite curve is monotone where
+	# the data is monotone and never overshoots its data values.
+	#
+	# Reference: Fritsch, F. N. and Carlson, R. E. (1980), "Monotone Piecewise
+	# Cubic Interpolation", SIAM Journal on Numerical Analysis, 17 (2): 238-246.
+	#
+	# Precondition: xs is strictly increasing and xs.size() == ys.size() >= 2.
+	func _fritsch_carlson_tangents(p_xs: PackedFloat32Array, p_ys: PackedFloat32Array) -> PackedFloat32Array:
+		var n := p_xs.size()
+		var m := PackedFloat32Array()
+		m.resize(n)
+
+		# Secant slopes between consecutive samples.
+		var d := PackedFloat32Array()
+		d.resize(n - 1)
+		for k in range(n - 1):
+			d[k] = (p_ys[k + 1] - p_ys[k]) / (p_xs[k + 1] - p_xs[k])
+
+		# Initial tangents: endpoint tangents copy the adjacent secant slope.
+		# Interior tangents are zero at extrema and the average of the two
+		# adjacent secants otherwise.
+		m[0] = d[0]
+		m[n - 1] = d[n - 2]
+		for k in range(1, n - 1):
+			if d[k - 1] * d[k] <= 0.0:
+				m[k] = 0.0
+			else:
+				m[k] = 0.5 * (d[k - 1] + d[k])
+
+		# Fritsch-Carlson monotonicity correction. For each segment, project
+		# the (m[k], m[k+1]) pair onto the disk of radius 3 in the (alpha,
+		# beta) plane to guarantee no overshoot.
+		for k in range(n - 1):
+			if d[k] == 0.0:
+				m[k] = 0.0
+				m[k + 1] = 0.0
+				continue
+			var alpha: float = m[k] / d[k]
+			var beta: float = m[k + 1] / d[k]
+			if alpha < 0.0:
+				m[k] = 0.0
+				alpha = 0.0
+			if beta < 0.0:
+				m[k + 1] = 0.0
+				beta = 0.0
+			var sq: float = alpha * alpha + beta * beta
+			if sq > 9.0:
+				var tau: float = 3.0 / sqrt(sq)
+				m[k] = tau * alpha * d[k]
+				m[k + 1] = tau * beta * d[k]
+
+		return m
+
+
 	####################################################################################################
 	# Series helpers
 	####################################################################################################
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd
index 80466dc..463c87a 100644
--- a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd
@@ -14,7 +14,9 @@ func _ready() -> void:
 	_setup_test_10()
 	_setup_test_11()
 	_setup_test_12()
-
+	_setup_test_13()
+	_setup_test_14()
+	_setup_test_15()
 
 ####################################################################################################
 # Helpers
@@ -23,7 +25,7 @@ func _ready() -> void:
 func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
 	var series_names := PackedStringArray(["Series A"])
 	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
-	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0])
 
 	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
 
@@ -38,6 +40,7 @@ func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpola
 	y_axis.type = TauAxisConfig.Type.CONTINUOUS
 	y_axis.scale = TauAxisConfig.Scale.LINEAR
 	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
 
 	var line_config := TauLineConfig.new()
 	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
@@ -64,7 +67,7 @@ func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpola
 func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
 	var series_names := PackedStringArray(["Series A"])
 	var x_a := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
-	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0])
 
 	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a], [y_a])
 
@@ -79,6 +82,7 @@ func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_inter
 	y_axis.type = TauAxisConfig.Type.CONTINUOUS
 	y_axis.scale = TauAxisConfig.Scale.LINEAR
 	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
 
 	var line_config := TauLineConfig.new()
 	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
@@ -105,7 +109,7 @@ func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_inter
 func make_shared_x_categorical_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
 	var series_names := PackedStringArray(["Series A"])
 	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
-	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0])
 
 	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a])
 
@@ -120,6 +124,7 @@ func make_shared_x_categorical_plot(p_plot: TauPlot, p_title: String, p_interpol
 	y_axis.type = TauAxisConfig.Type.CONTINUOUS
 	y_axis.scale = TauAxisConfig.Scale.LINEAR
 	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
 
 	var line_config := TauLineConfig.new()
 	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
@@ -226,3 +231,24 @@ func _setup_test_11() -> void:
 
 func _setup_test_12() -> void:
 	make_shared_x_categorical_plot(%TestPlot12, "[STEP_AFTER] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 13
+####################################################################################################
+
+func _setup_test_13() -> void:
+	make_shared_x_continuous_plot(%TestPlot13, "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+####################################################################################################
+# Test 14
+####################################################################################################
+
+func _setup_test_14() -> void:
+	make_per_series_x_continuous_plot(%TestPlot14, "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+####################################################################################################
+# Test 15
+####################################################################################################
+
+func _setup_test_15() -> void:
+	make_shared_x_categorical_plot(%TestPlot15, "[SMOOTH_MONOTONE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn
index 57f6107..8db02d7 100644
--- a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn
@@ -155,3 +155,36 @@ script = ExtResource("2_nry5o")
 title = "[STEP_AFTER] SHARED_X + CATEGORICAL"
 legend_enabled = false
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot13" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot14" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot15" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_nry5o")
+title = "[SMOOTH_MONOTONE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd
index 564bc96..1a24559 100644
--- a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd
@@ -10,7 +10,8 @@ func _ready() -> void:
 	_setup_test_6()
 	_setup_test_7()
 	_setup_test_8()
-
+	_setup_test_9()
+	_setup_test_10()
 
 ####################################################################################################
 # Helpers
@@ -19,7 +20,7 @@ func _ready() -> void:
 func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
 	var series_names := PackedStringArray(["Series A"])
 	var x := PackedFloat64Array([pow(10, -2), pow(10, -1), pow(10, 0), pow(10, 1), pow(10, 2)])
-	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0])
 
 	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
 
@@ -35,6 +36,7 @@ func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpola
 	y_axis.type = TauAxisConfig.Type.CONTINUOUS
 	y_axis.scale = TauAxisConfig.Scale.LINEAR
 	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
 
 	var line_config := TauLineConfig.new()
 	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
@@ -61,7 +63,7 @@ func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpola
 func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
 	var series_names := PackedStringArray(["Series A"])
 	var x_a := PackedFloat64Array([pow(10, -2), pow(10, -1), pow(10, 0), pow(10, 1), pow(10, 2)])
-	var y_a := PackedFloat64Array([10.0, 20.0, 30.0, 40.0, 50.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0])
 
 	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a], [y_a])
 
@@ -77,6 +79,7 @@ func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_inter
 	y_axis.type = TauAxisConfig.Type.CONTINUOUS
 	y_axis.scale = TauAxisConfig.Scale.LINEAR
 	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
 
 	var line_config := TauLineConfig.new()
 	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
@@ -155,3 +158,17 @@ func _setup_test_7() -> void:
 
 func _setup_test_8() -> void:
 	make_per_series_x_continuous_plot(%TestPlot8, "[STEP_AFTER] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_continuous_plot(%TestPlot9, "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+####################################################################################################
+# Test 10
+####################################################################################################
+
+func _setup_test_10() -> void:
+	make_per_series_x_continuous_plot(%TestPlot10, "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
index cb19e48..5842c19 100644
--- a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
@@ -111,3 +111,25 @@ script = ExtResource("2_u5as0")
 title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
 legend_enabled = false
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot10" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_u5as0")
+title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"

From dde3dde1939a1165715be00d8df6b3cc80cc2421 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Mon, 27 Apr 2026 12:51:53 +0200
Subject: [PATCH 07/23] Implement dash lines

---
 addons/tau-plot/plot/xy/line/line_renderer.gd |  97 ++++++++++++--
 addons/tau-plot/plot/xy/line/line_style.gd    |  18 ++-
 .../tests/line/dash/test_line_dash.gd         | 122 ++++++++++++++++++
 .../tests/line/dash/test_line_dash.gd.uid     |   1 +
 .../tests/line/dash/test_line_dash.tscn       | 115 +++++++++++++++++
 5 files changed, 338 insertions(+), 15 deletions(-)
 create mode 100644 addons/tau-plot/tests/line/dash/test_line_dash.gd
 create mode 100644 addons/tau-plot/tests/line/dash/test_line_dash.gd.uid
 create mode 100644 addons/tau-plot/tests/line/dash/test_line_dash.tscn

diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index 361d74e..a6912f7 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -11,8 +11,8 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 # Draws line overlays from an XYLayout + Dataset.
 #
 # This renderer reads all samples through the Dataset public API (no direct
-# buffer/series access). One contiguous run of valid samples produces one
-# draw_polyline() call per series.
+# buffer/series access). Each contiguous run of valid samples is drawn with
+# one Godot draw call.
 #
 # Runtime behavior:
 # - NaN and Inf X or Y values are treated according to TauLineConfig.gap_policy.
@@ -27,11 +27,22 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 #   intermediate points in screen space into the polyline. SMOOTH_MONOTONE
 #   replaces each segment with a fixed number of sub-samples from a
 #   Fritsch-Carlson piecewise cubic Hermite curve evaluated in screen space.
-#   Whichever interpolation is active, a contiguous run is still drawn with a
+#
+# Rendering path selection:
+# - Path 1, fast path: TauLineStyle.dash_px == 0. The run is drawn with a
 #   single draw_polyline() call.
+# - Path 2, dashed batched path: TauLineStyle.dash_px > 0. Dash phase is
+#   precomputed across the full run, the "on" intervals are collected into a
+#   flat segment array, and the run is drawn with a single draw_multiline()
+#   call. The dash phase is continuous across all segments of the polyline.
 #
 # LineValidator is expected to enforce binding-level typing constraints.
 class LineRenderer extends Control:
+	# Number of sub-segments inserted between two consecutive samples by
+	# SMOOTH_MONOTONE. The value balances visual smoothness on a typical
+	# screen against the per-segment cost paid by draw_polyline().
+	const _SMOOTH_SUBDIVISIONS: int = 16
+
 	var _layout: XYLayout = null
 	var _dataset: Dataset = null
 	var _line_config: TauLineConfig = null
@@ -233,27 +244,85 @@ class LineRenderer extends Control:
 		p_run.append(p_point)
 
 
-	####################################################################################################
-	# Smooth-monotone (Fritsch-Carlson) resampling
-	####################################################################################################
-
-	# Number of sub-segments inserted between two consecutive samples by
-	# SMOOTH_MONOTONE. The value balances visual smoothness on a typical
-	# screen against the per-segment cost paid by draw_polyline().
-	const _SMOOTH_SUBDIVISIONS: int = 16
-
-
 	# Draw the polyline for one buffered run.
 	# For LINEAR and the step modes the buffered run is already the final polyline.
 	# For SMOOTH_MONOTONE the run is first replaced by its Fritsch-Carlson piecewise cubic resampling.
 	# Runs of fewer than two points are silently dropped.
+	#
+	# When TauLineStyle.dash_px is 0, the polyline is emitted via path 1
+	# (draw_polyline). Otherwise it is emitted via path 2: dash phase is
+	# precomputed across the whole polyline and the resulting "on" intervals
+	# are flushed in a single draw_multiline() call.
 	func _finalize_run(p_run: PackedVector2Array, p_color: Color, p_width_px: float, p_mode: TauLineConfig.InterpolationMode) -> void:
 		var polyline: PackedVector2Array = p_run
 		if p_mode == TauLineConfig.InterpolationMode.SMOOTH_MONOTONE and p_run.size() > 2:
 			polyline = _resample_smooth_monotone(p_run)
-		if polyline.size() >= 2:
+		if polyline.size() < 2:
+			return
+
+		var dash_px: int = max(_line_style.dash_px, 0)
+		if dash_px <= 0:
 			draw_polyline(polyline, p_color, p_width_px)
+		else:
+			_draw_dashed_polyline(polyline, p_color, p_width_px, float(dash_px))
+
 
+	# Builds the flat segment array of "on" dash intervals along p_polyline and
+	# emits it with a single draw_multiline() call. The dash period is
+	# 2 * p_dash_px (one "on" length followed by one "off" length of equal
+	# size). Dash phase is tracked as a single scalar that advances along the
+	# polyline arc length, so the pattern is continuous across consecutive
+	# segments and does not reset at sample positions.
+	#
+	# Degenerate segments (zero length) are skipped: they cannot carry any
+	# dash and do not advance the phase.
+	func _draw_dashed_polyline(p_polyline: PackedVector2Array, p_color: Color, p_width_px: float, p_dash_px: float) -> void:
+		var period: float = p_dash_px * 2.0
+		var n := p_polyline.size()
+		var phase: float = 0.0
+		var segments := PackedVector2Array()
+
+		for i in range(n - 1):
+			var seg_start: Vector2 = p_polyline[i]
+			var seg_end: Vector2 = p_polyline[i + 1]
+			var seg_vec: Vector2 = seg_end - seg_start
+			var seg_len: float = seg_vec.length()
+			if seg_len <= 0.0:
+				continue
+
+			var seg_dir: Vector2 = seg_vec / seg_len
+
+			# Position along the current segment, in pixels from seg_start.
+			# Phase 0..p_dash_px is "on", p_dash_px..period is "off".
+			var pos: float = 0.0
+			while pos < seg_len:
+				var phase_in_period: float = phase
+				if phase_in_period < p_dash_px:
+					# Currently inside an "on" interval.
+					var remaining_on: float = p_dash_px - phase_in_period
+					var on_end: float = min(pos + remaining_on, seg_len)
+					segments.append(seg_start + seg_dir * pos)
+					segments.append(seg_start + seg_dir * on_end)
+					var consumed: float = on_end - pos
+					phase += consumed
+					pos = on_end
+				else:
+					# Currently inside an "off" interval.
+					var remaining_off: float = period - phase_in_period
+					var off_end: float = min(pos + remaining_off, seg_len)
+					var consumed_off: float = off_end - pos
+					phase += consumed_off
+					pos = off_end
+
+				if phase >= period:
+					phase -= period
+
+		if segments.size() >= 2:
+			draw_multiline(segments, p_color, p_width_px)
+
+	####################################################################################################
+	# Smooth-monotone (Fritsch-Carlson) resampling
+	####################################################################################################
 
 	# Builds the Fritsch-Carlson piecewise cubic Hermite curve through p_points
 	# and returns it sampled at _SMOOTH_SUBDIVISIONS sub-segments per input
diff --git a/addons/tau-plot/plot/xy/line/line_style.gd b/addons/tau-plot/plot/xy/line/line_style.gd
index 9d90fe3..0b293bc 100644
--- a/addons/tau-plot/plot/xy/line/line_style.gd
+++ b/addons/tau-plot/plot/xy/line/line_style.gd
@@ -21,6 +21,12 @@ class_name TauLineStyle extends Resource
 const DEFAULT_LINE_WIDTH_PX: float = 2.0
 @export var line_width_px: float = DEFAULT_LINE_WIDTH_PX
 
+## Dash length in pixels. A value of 0 produces a solid line. Any positive
+## value switches the line to dashed rendering with alternating on-off
+## segments of that pixel length.
+const DEFAULT_LINE_DASH_PX: int = 0
+@export var dash_px: int = DEFAULT_LINE_DASH_PX
+
 
 ####################################################################################################
 # Cascade: theme loading (layer 2)
@@ -39,13 +45,18 @@ func load_from_theme(p_control: Control, p_pane_index: int) -> void:
 		push_error("TauLineStyle.load_from_theme(): control is null")
 		return
 
-	# line_width_px
 	if p_control.has_theme_constant(&"line_width_px"):
 		line_width_px = max(float(p_control.get_theme_constant(&"line_width_px")), 0.0)
 	var indexed_width_key := StringName("line_width_px_%d" % p_pane_index)
 	if p_control.has_theme_constant(indexed_width_key):
 		line_width_px = max(float(p_control.get_theme_constant(indexed_width_key)), 0.0)
 
+	if p_control.has_theme_constant(&"line_dash_px"):
+		dash_px = max(int(p_control.get_theme_constant(&"line_dash_px")), 0)
+	var indexed_dash_key := StringName("line_dash_px_%d" % p_pane_index)
+	if p_control.has_theme_constant(indexed_dash_key):
+		dash_px = max(int(p_control.get_theme_constant(indexed_dash_key)), 0)
+
 
 ####################################################################################################
 # Cascade: user overrides (layer 3)
@@ -61,6 +72,9 @@ func apply_overrides_from(p_user_style: TauLineStyle) -> void:
 	if p_user_style.line_width_px != DEFAULT_LINE_WIDTH_PX:
 		line_width_px = p_user_style.line_width_px
 
+	if p_user_style.dash_px != DEFAULT_LINE_DASH_PX:
+		dash_px = p_user_style.dash_px
+
 
 ####################################################################################################
 # Full cascade resolution
@@ -96,6 +110,8 @@ func is_equal_to(p_other: TauLineStyle) -> bool:
 		return false
 	if line_width_px != p_other.line_width_px:
 		return false
+	if dash_px != p_other.dash_px:
+		return false
 	return true
 
 
diff --git a/addons/tau-plot/tests/line/dash/test_line_dash.gd b/addons/tau-plot/tests/line/dash/test_line_dash.gd
new file mode 100644
index 0000000..d45021e
--- /dev/null
+++ b/addons/tau-plot/tests/line/dash/test_line_dash.gd
@@ -0,0 +1,122 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+	_setup_test_9()
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode, p_dash_px: int) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+
+	p_plot.title = p_title
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.style.dash_px = p_dash_px
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "LINEAR + dash = 2", TauLineConfig.InterpolationMode.LINEAR, 2)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_shared_x_continuous_plot(%TestPlot2, "LINEAR + dash = 4", TauLineConfig.InterpolationMode.LINEAR, 4)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "LINEAR + dash = 8", TauLineConfig.InterpolationMode.LINEAR, 8)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "STEP_MIDDLE + dash = 2", TauLineConfig.InterpolationMode.STEP_MIDDLE, 2)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "STEP_MIDDLE + dash = 4", TauLineConfig.InterpolationMode.STEP_MIDDLE, 4)
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_shared_x_continuous_plot(%TestPlot6, "STEP_MIDDLE + dash = 8", TauLineConfig.InterpolationMode.STEP_MIDDLE, 8)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "SMOOTH_MONOTONE + dash = 2", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 2)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_shared_x_continuous_plot(%TestPlot8, "SMOOTH_MONOTONE + dash = 4", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 4)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_continuous_plot(%TestPlot9, "SMOOTH_MONOTONE + dash = 8", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 8)
diff --git a/addons/tau-plot/tests/line/dash/test_line_dash.gd.uid b/addons/tau-plot/tests/line/dash/test_line_dash.gd.uid
new file mode 100644
index 0000000..8828a78
--- /dev/null
+++ b/addons/tau-plot/tests/line/dash/test_line_dash.gd.uid
@@ -0,0 +1 @@
+uid://ccebd3cs615t7
diff --git a/addons/tau-plot/tests/line/dash/test_line_dash.tscn b/addons/tau-plot/tests/line/dash/test_line_dash.tscn
new file mode 100644
index 0000000..d7b61ae
--- /dev/null
+++ b/addons/tau-plot/tests/line/dash/test_line_dash.tscn
@@ -0,0 +1,115 @@
+[gd_scene load_steps=3 format=3 uid="uid://f5gbq1v64in0"]
+
+[ext_resource type="Script" uid="uid://ccebd3cs615t7" path="res://addons/tau-plot/tests/line/dash/test_line_dash.gd" id="1_4q4uh"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_mp1bp"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_4q4uh")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Different dash lines"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_mp1bp")
+title = "LINEAR + dash = 2 for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_mp1bp")
+title = "LINEAR + dash = 4 for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_mp1bp")
+title = "LINEAR + dash = 8 for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_mp1bp")
+title = "STEP_MIDDLE + dash = 2 for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_mp1bp")
+title = "STEP_MIDDLE + dash = 4 for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_mp1bp")
+title = "STEP_MIDDLE + dash = 8 for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_mp1bp")
+title = "SMOOTH_MONOTONE + dash = 2 for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_mp1bp")
+title = "SMOOTH_MONOTONE + dash = 4 for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_mp1bp")
+title = "SMOOTH_MONOTONE + dash = 8 for series A"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"

From 7f6e160ae2c0d92a9759ac3c2ea4facffcfba748 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Mon, 27 Apr 2026 18:17:32 +0200
Subject: [PATCH 08/23] Per-series dash length refactoring

---
 addons/tau-plot/plot/xy/line/line_renderer.gd | 45 +++++----
 addons/tau-plot/plot/xy/line/line_style.gd    | 95 +++++++++++++++----
 .../tests/line/dash/test_line_dash.gd         | 34 ++++---
 .../test_line_interpolation_logarithmic.tscn  |  4 +-
 4 files changed, 128 insertions(+), 50 deletions(-)

diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index a6912f7..6903bfb 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -28,13 +28,19 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 #   replaces each segment with a fixed number of sub-samples from a
 #   Fritsch-Carlson piecewise cubic Hermite curve evaluated in screen space.
 #
-# Rendering path selection:
-# - Path 1, fast path: TauLineStyle.dash_px == 0. The run is drawn with a
-#   single draw_polyline() call.
-# - Path 2, dashed batched path: TauLineStyle.dash_px > 0. Dash phase is
-#   precomputed across the full run, the "on" intervals are collected into a
-#   flat segment array, and the run is drawn with a single draw_multiline()
-#   call. The dash phase is continuous across all segments of the polyline.
+# Rendering path selection (per series):
+# - The active dash length for a series is resolved from
+#   TauLineStyle.dash_lengths_px through the helper
+#   TauLineStyle.get_series_dash_px(global_series_index). Path selection is
+#   therefore per series: two series in the same overlay can run on
+#   different paths in the same frame.
+# - Path 1, fast path: resolved per-series dash length is 0. The run is
+#   drawn with a single draw_polyline() call.
+# - Path 2, dashed batched path: resolved per-series dash length is positive.
+#   Dash phase is precomputed across the full run, the "on" intervals are
+#   collected into a flat segment array, and the run is drawn with a single
+#   draw_multiline() call. The dash phase is continuous across all segments
+#   of the polyline.
 #
 # LineValidator is expected to enforce binding-level typing constraints.
 class LineRenderer extends Control:
@@ -166,6 +172,7 @@ class LineRenderer extends Control:
 		var series_id := _get_line_series_id(p_series_index)
 		var global_series_index := _get_global_series_index(p_series_index)
 		var color := _resolve_series_color(global_series_index)
+		var dash_px: int = _line_style.get_series_dash_px(global_series_index)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
@@ -179,14 +186,14 @@ class LineRenderer extends Control:
 			var x_value: float = float(_dataset.get_shared_x(i)) if is_shared_x else float(_dataset.get_series_x(series_id, i))
 			if is_nan(x_value) or is_inf(x_value) or not _is_x_value_valid_for_scale(x_value):
 				if not bridge:
-					_finalize_run(run, color, p_width_px, interpolation)
+					_finalize_run(run, color, p_width_px, interpolation, dash_px)
 					run = PackedVector2Array()
 				continue
 
 			var y_value := _dataset.get_series_y(series_id, i)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					_finalize_run(run, color, p_width_px, interpolation)
+					_finalize_run(run, color, p_width_px, interpolation, dash_px)
 					run = PackedVector2Array()
 				continue
 
@@ -194,13 +201,14 @@ class LineRenderer extends Control:
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
 			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
 
-		_finalize_run(run, color, p_width_px, interpolation)
+		_finalize_run(run, color, p_width_px, interpolation, dash_px)
 
 
 	func _draw_series_categorical(p_series_index: int, p_width_px: float) -> void:
 		var series_id := _get_line_series_id(p_series_index)
 		var global_series_index := _get_global_series_index(p_series_index)
 		var color := _resolve_series_color(global_series_index)
+		var dash_px: int = _line_style.get_series_dash_px(global_series_index)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
@@ -212,7 +220,7 @@ class LineRenderer extends Control:
 			var y_value := _dataset.get_series_y(series_id, cat_idx)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					_finalize_run(run, color, p_width_px, interpolation)
+					_finalize_run(run, color, p_width_px, interpolation, dash_px)
 					run = PackedVector2Array()
 				continue
 
@@ -220,7 +228,7 @@ class LineRenderer extends Control:
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
 			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
 
-		_finalize_run(run, color, p_width_px, interpolation)
+		_finalize_run(run, color, p_width_px, interpolation, dash_px)
 
 
 	func _append_with_interpolation(p_run: PackedVector2Array, p_point: Vector2, p_mode: TauLineConfig.InterpolationMode) -> void:
@@ -249,18 +257,19 @@ class LineRenderer extends Control:
 	# For SMOOTH_MONOTONE the run is first replaced by its Fritsch-Carlson piecewise cubic resampling.
 	# Runs of fewer than two points are silently dropped.
 	#
-	# When TauLineStyle.dash_px is 0, the polyline is emitted via path 1
-	# (draw_polyline). Otherwise it is emitted via path 2: dash phase is
-	# precomputed across the whole polyline and the resulting "on" intervals
-	# are flushed in a single draw_multiline() call.
-	func _finalize_run(p_run: PackedVector2Array, p_color: Color, p_width_px: float, p_mode: TauLineConfig.InterpolationMode) -> void:
+	# When p_dash_px is 0, the polyline is emitted via path 1 (draw_polyline).
+	# Otherwise it is emitted via path 2: dash phase is precomputed across the
+	# whole polyline and the resulting "on" intervals are flushed in a single
+	# draw_multiline() call. p_dash_px is the resolved per-series dash length
+	# obtained from TauLineStyle.get_series_dash_px().
+	func _finalize_run(p_run: PackedVector2Array, p_color: Color, p_width_px: float, p_mode: TauLineConfig.InterpolationMode, p_dash_px: int) -> void:
 		var polyline: PackedVector2Array = p_run
 		if p_mode == TauLineConfig.InterpolationMode.SMOOTH_MONOTONE and p_run.size() > 2:
 			polyline = _resample_smooth_monotone(p_run)
 		if polyline.size() < 2:
 			return
 
-		var dash_px: int = max(_line_style.dash_px, 0)
+		var dash_px: int = max(p_dash_px, 0)
 		if dash_px <= 0:
 			draw_polyline(polyline, p_color, p_width_px)
 		else:
diff --git a/addons/tau-plot/plot/xy/line/line_style.gd b/addons/tau-plot/plot/xy/line/line_style.gd
index 0b293bc..4bf68f7 100644
--- a/addons/tau-plot/plot/xy/line/line_style.gd
+++ b/addons/tau-plot/plot/xy/line/line_style.gd
@@ -21,11 +21,27 @@ class_name TauLineStyle extends Resource
 const DEFAULT_LINE_WIDTH_PX: float = 2.0
 @export var line_width_px: float = DEFAULT_LINE_WIDTH_PX
 
-## Dash length in pixels. A value of 0 produces a solid line. Any positive
-## value switches the line to dashed rendering with alternating on-off
-## segments of that pixel length.
-const DEFAULT_LINE_DASH_PX: int = 0
-@export var dash_px: int = DEFAULT_LINE_DASH_PX
+## Per-series dash length cycle, in pixels. Each entry sets the dash length
+## for one series, with the array indexed cyclically by series index using
+## modulo: series [code]i[/code] reads entry
+## [code]i % dash_lengths_px.size()[/code]. An entry of [code]0[/code]
+## produces a solid line for that series. Any positive entry switches that
+## series to dashed rendering with alternating on-off segments of that pixel
+## length. An empty array is treated as all series solid.
+const DEFAULT_DASH_LENGTHS_PX: Array[int] = [0]
+@export var dash_lengths_px: Array[int] = [0]
+
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+## Returns the resolved dash length in pixels for the given series index.
+func get_series_dash_px(p_series_index: int) -> int:
+	if dash_lengths_px.is_empty():
+		return 0
+	var entry: int = dash_lengths_px[p_series_index % dash_lengths_px.size()]
+	return max(entry, 0)
 
 
 ####################################################################################################
@@ -34,9 +50,15 @@ const DEFAULT_LINE_DASH_PX: int = 0
 
 ## Loads properties from the Godot theme attached to [param p_control].
 ##
-## For each property, the non-indexed theme key is fetched first (shared base
-## for all panes), then the indexed key for [param p_pane_index] overwrites it
-## if present.
+## For scalar properties, the non-indexed theme key is fetched first (shared
+## base for all panes), then the indexed key for [param p_pane_index]
+## overwrites it if present.
+##
+## For [code]dash_lengths_px[/code], the same convention applies at series
+## granularity:
+##   1. [code]line_dash_px_N[/code] sets the dash length for series N across
+##      all panes.
+##   2. [code]line_dash_px_N_P[/code] overrides series N in pane P only.
 ##
 ## This method writes every property unconditionally because it is called on
 ## the resolved instance, not on the user-provided resource.
@@ -45,17 +67,39 @@ func load_from_theme(p_control: Control, p_pane_index: int) -> void:
 		push_error("TauLineStyle.load_from_theme(): control is null")
 		return
 
+	# line_width_px
 	if p_control.has_theme_constant(&"line_width_px"):
 		line_width_px = max(float(p_control.get_theme_constant(&"line_width_px")), 0.0)
 	var indexed_width_key := StringName("line_width_px_%d" % p_pane_index)
 	if p_control.has_theme_constant(indexed_width_key):
 		line_width_px = max(float(p_control.get_theme_constant(indexed_width_key)), 0.0)
 
-	if p_control.has_theme_constant(&"line_dash_px"):
-		dash_px = max(int(p_control.get_theme_constant(&"line_dash_px")), 0)
-	var indexed_dash_key := StringName("line_dash_px_%d" % p_pane_index)
-	if p_control.has_theme_constant(indexed_dash_key):
-		dash_px = max(int(p_control.get_theme_constant(indexed_dash_key)), 0)
+	# dash_lengths_px: two-level indexed lookup.
+	# Level 1 (global): line_dash_px_N
+	var global_dashes: Array[int] = []
+	var dash_index := 0
+	while true:
+		var key := "line_dash_px_%d" % dash_index
+		if not p_control.has_theme_constant(key):
+			break
+		global_dashes.append(max(int(p_control.get_theme_constant(key)), 0))
+		dash_index += 1
+
+	if not global_dashes.is_empty():
+		dash_lengths_px = global_dashes
+
+	# Level 2 (per-pane): line_dash_px_N_P overrides series N in pane P.
+	var pane_dash_index := 0
+	while true:
+		var key := "line_dash_px_%d_%d" % [pane_dash_index, p_pane_index]
+		if not p_control.has_theme_constant(key):
+			break
+		# Grow the array if the per-pane theme defines more dash entries than
+		# the global theme (or the default).
+		if pane_dash_index >= dash_lengths_px.size():
+			dash_lengths_px.resize(pane_dash_index + 1)
+		dash_lengths_px[pane_dash_index] = max(int(p_control.get_theme_constant(key)), 0)
+		pane_dash_index += 1
 
 
 ####################################################################################################
@@ -72,8 +116,9 @@ func apply_overrides_from(p_user_style: TauLineStyle) -> void:
 	if p_user_style.line_width_px != DEFAULT_LINE_WIDTH_PX:
 		line_width_px = p_user_style.line_width_px
 
-	if p_user_style.dash_px != DEFAULT_LINE_DASH_PX:
-		dash_px = p_user_style.dash_px
+	# dash_lengths_px: element-wise comparison against the default array.
+	if _is_dash_lengths_overridden(p_user_style.dash_lengths_px):
+		dash_lengths_px = p_user_style.dash_lengths_px.duplicate()
 
 
 ####################################################################################################
@@ -110,8 +155,11 @@ func is_equal_to(p_other: TauLineStyle) -> bool:
 		return false
 	if line_width_px != p_other.line_width_px:
 		return false
-	if dash_px != p_other.dash_px:
+	if dash_lengths_px.size() != p_other.dash_lengths_px.size():
 		return false
+	for i in range(dash_lengths_px.size()):
+		if dash_lengths_px[i] != p_other.dash_lengths_px[i]:
+			return false
 	return true
 
 
@@ -119,3 +167,18 @@ func is_equal_to(p_other: TauLineStyle) -> bool:
 # drawn within a fixed domain but do not affect domain, ticks, or pane rect.
 func has_layout_affecting_change(p_other: TauLineStyle) -> bool:
 	return false
+
+
+####################################################################################################
+# Private
+####################################################################################################
+
+## Returns true if [param p_dashes] differs from DEFAULT_DASH_LENGTHS_PX using
+## a size + element loop (safest approach for typed arrays in GDScript).
+static func _is_dash_lengths_overridden(p_dashes: Array[int]) -> bool:
+	if p_dashes.size() != DEFAULT_DASH_LENGTHS_PX.size():
+		return true
+	for i in range(p_dashes.size()):
+		if p_dashes[i] != DEFAULT_DASH_LENGTHS_PX[i]:
+			return true
+	return false
diff --git a/addons/tau-plot/tests/line/dash/test_line_dash.gd b/addons/tau-plot/tests/line/dash/test_line_dash.gd
index d45021e..d986ae2 100644
--- a/addons/tau-plot/tests/line/dash/test_line_dash.gd
+++ b/addons/tau-plot/tests/line/dash/test_line_dash.gd
@@ -16,12 +16,13 @@ func _ready() -> void:
 # Helpers
 ####################################################################################################
 
-func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode, p_dash_px: int) -> void:
-	var series_names := PackedStringArray(["Series A"])
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode, p_series_a_dash_px: int) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
 	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
 	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0])
+	var y_b := PackedFloat64Array([20.0, 12.0, 23.0, 7.0, 29.0])
 
-	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
 
 	p_plot.title = p_title
 
@@ -38,7 +39,7 @@ func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpola
 	var line_config := TauLineConfig.new()
 	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
 	line_config.interpolation_mode = p_interpolation
-	line_config.style.dash_px = p_dash_px
+	line_config.style.dash_lengths_px = [p_series_a_dash_px, 0]
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -53,7 +54,12 @@ func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpola
 	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
 	sb_a.y_axis_id = TauPlot.AxisId.LEFT
 
-	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
 
 	p_plot.plot_xy(dataset, config, bindings)
 
@@ -63,60 +69,60 @@ func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpola
 ####################################################################################################
 
 func _setup_test_1() -> void:
-	make_shared_x_continuous_plot(%TestPlot1, "LINEAR + dash = 2", TauLineConfig.InterpolationMode.LINEAR, 2)
+	make_shared_x_continuous_plot(%TestPlot1, "LINEAR + dash = 2 for series A", TauLineConfig.InterpolationMode.LINEAR, 2)
 
 ####################################################################################################
 # Test 2
 ####################################################################################################
 
 func _setup_test_2() -> void:
-	make_shared_x_continuous_plot(%TestPlot2, "LINEAR + dash = 4", TauLineConfig.InterpolationMode.LINEAR, 4)
+	make_shared_x_continuous_plot(%TestPlot2, "LINEAR + dash = 4 for series A", TauLineConfig.InterpolationMode.LINEAR, 4)
 
 ####################################################################################################
 # Test 3
 ####################################################################################################
 
 func _setup_test_3() -> void:
-	make_shared_x_continuous_plot(%TestPlot3, "LINEAR + dash = 8", TauLineConfig.InterpolationMode.LINEAR, 8)
+	make_shared_x_continuous_plot(%TestPlot3, "LINEAR + dash = 8 for series A", TauLineConfig.InterpolationMode.LINEAR, 8)
 
 ####################################################################################################
 # Test 4
 ####################################################################################################
 
 func _setup_test_4() -> void:
-	make_shared_x_continuous_plot(%TestPlot4, "STEP_MIDDLE + dash = 2", TauLineConfig.InterpolationMode.STEP_MIDDLE, 2)
+	make_shared_x_continuous_plot(%TestPlot4, "STEP_MIDDLE + dash = 2 for series A", TauLineConfig.InterpolationMode.STEP_MIDDLE, 2)
 
 ####################################################################################################
 # Test 5
 ####################################################################################################
 
 func _setup_test_5() -> void:
-	make_shared_x_continuous_plot(%TestPlot5, "STEP_MIDDLE + dash = 4", TauLineConfig.InterpolationMode.STEP_MIDDLE, 4)
+	make_shared_x_continuous_plot(%TestPlot5, "STEP_MIDDLE + dash = 4 for series A", TauLineConfig.InterpolationMode.STEP_MIDDLE, 4)
 
 ####################################################################################################
 # Test 6
 ####################################################################################################
 
 func _setup_test_6() -> void:
-	make_shared_x_continuous_plot(%TestPlot6, "STEP_MIDDLE + dash = 8", TauLineConfig.InterpolationMode.STEP_MIDDLE, 8)
+	make_shared_x_continuous_plot(%TestPlot6, "STEP_MIDDLE + dash = 8 for series A", TauLineConfig.InterpolationMode.STEP_MIDDLE, 8)
 
 ####################################################################################################
 # Test 7
 ####################################################################################################
 
 func _setup_test_7() -> void:
-	make_shared_x_continuous_plot(%TestPlot7, "SMOOTH_MONOTONE + dash = 2", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 2)
+	make_shared_x_continuous_plot(%TestPlot7, "SMOOTH_MONOTONE + dash = 2 for series A", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 2)
 
 ####################################################################################################
 # Test 8
 ####################################################################################################
 
 func _setup_test_8() -> void:
-	make_shared_x_continuous_plot(%TestPlot8, "SMOOTH_MONOTONE + dash = 4", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 4)
+	make_shared_x_continuous_plot(%TestPlot8, "SMOOTH_MONOTONE + dash = 4 for series A", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 4)
 
 ####################################################################################################
 # Test 9
 ####################################################################################################
 
 func _setup_test_9() -> void:
-	make_shared_x_continuous_plot(%TestPlot9, "SMOOTH_MONOTONE + dash = 8", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 8)
+	make_shared_x_continuous_plot(%TestPlot9, "SMOOTH_MONOTONE + dash = 8 for series A", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 8)
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
index 5842c19..7557394 100644
--- a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
@@ -119,7 +119,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_u5as0")
-title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
+title = "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS"
 legend_enabled = false
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
@@ -130,6 +130,6 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_u5as0")
-title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
+title = "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS"
 legend_enabled = false
 metadata/_custom_type_script = "uid://dnhvsf2wip771"

From 8cb7999b05f76a20e9f95fb6c6adaa58b3b3c919 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Mon, 27 Apr 2026 18:19:15 +0200
Subject: [PATCH 09/23] Per-series line width refactoring

---
 addons/tau-plot/plot/xy/line/line_config.gd   |  2 +-
 addons/tau-plot/plot/xy/line/line_renderer.gd | 35 +++++---
 addons/tau-plot/plot/xy/line/line_style.gd    | 89 +++++++++++++++----
 .../plot/xy/line/line_visual_attributes.gd    |  1 -
 .../plot/xy/line/line_visual_callbacks.gd     |  1 -
 5 files changed, 92 insertions(+), 36 deletions(-)

diff --git a/addons/tau-plot/plot/xy/line/line_config.gd b/addons/tau-plot/plot/xy/line/line_config.gd
index 73aced2..2424ad4 100644
--- a/addons/tau-plot/plot/xy/line/line_config.gd
+++ b/addons/tau-plot/plot/xy/line/line_config.gd
@@ -9,7 +9,7 @@ const LineVisualCallbacks := preload("res://addons/tau-plot/plot/xy/line/line_vi
 ################################################################################################
 
 ## Theme-driven visual parameters for lines.
-## Never null. Modify properties directly: line_config.style.line_width_px = 3.0.
+## Never null. Modify properties directly: line_config.style.line_widths_px = [3.0].
 ## Properties set this way are automatically guarded from theme overwriting.
 @export var style: TauLineStyle = TauLineStyle.new()
 
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index 6903bfb..b2cc876 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -29,6 +29,10 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 #   Fritsch-Carlson piecewise cubic Hermite curve evaluated in screen space.
 #
 # Rendering path selection (per series):
+# - The active line width for a series is resolved from
+#   TauLineStyle.line_widths_px through the helper
+#   TauLineStyle.get_series_width_px(global_series_index). A series whose
+#   resolved width is 0 is skipped entirely.
 # - The active dash length for a series is resolved from
 #   TauLineStyle.dash_lengths_px through the helper
 #   TauLineStyle.get_series_dash_px(global_series_index). Path selection is
@@ -143,13 +147,10 @@ class LineRenderer extends Control:
 			return
 
 		var draw_order := _get_series_draw_order(series_count)
-		var width_px: float = max(_line_style.line_width_px, 0.0)
-		if width_px <= 0.0:
-			return
 
 		for draw_rank in range(draw_order.size()):
 			var series_index: int = draw_order[draw_rank]
-			_draw_series_independent(series_index, width_px)
+			_draw_series_independent(series_index)
 
 
 	# Draws a single series as one or more polyline runs, respecting the
@@ -160,18 +161,21 @@ class LineRenderer extends Control:
 	#     - SKIP   flushes the current run and starts a new one.
 	#     - BRIDGE drops the sample and keeps appending into the same run.
 	#   - A run of fewer than two points is discarded (no polyline).
-	func _draw_series_independent(p_series_index: int, p_width_px: float) -> void:
+	func _draw_series_independent(p_series_index: int) -> void:
 		var x_cfg := _get_x_axis_config()
 		if x_cfg != null and x_cfg.type == TauAxisConfig.Type.CATEGORICAL:
-			_draw_series_categorical(p_series_index, p_width_px)
+			_draw_series_categorical(p_series_index)
 		else:
-			_draw_series_continuous(p_series_index, p_width_px)
+			_draw_series_continuous(p_series_index)
 
 
-	func _draw_series_continuous(p_series_index: int, p_width_px: float) -> void:
+	func _draw_series_continuous(p_series_index: int) -> void:
 		var series_id := _get_line_series_id(p_series_index)
 		var global_series_index := _get_global_series_index(p_series_index)
 		var color := _resolve_series_color(global_series_index)
+		var width_px: float = _line_style.get_series_width_px(global_series_index)
+		if width_px <= 0.0:
+			return
 		var dash_px: int = _line_style.get_series_dash_px(global_series_index)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
@@ -186,14 +190,14 @@ class LineRenderer extends Control:
 			var x_value: float = float(_dataset.get_shared_x(i)) if is_shared_x else float(_dataset.get_series_x(series_id, i))
 			if is_nan(x_value) or is_inf(x_value) or not _is_x_value_valid_for_scale(x_value):
 				if not bridge:
-					_finalize_run(run, color, p_width_px, interpolation, dash_px)
+					_finalize_run(run, color, width_px, interpolation, dash_px)
 					run = PackedVector2Array()
 				continue
 
 			var y_value := _dataset.get_series_y(series_id, i)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					_finalize_run(run, color, p_width_px, interpolation, dash_px)
+					_finalize_run(run, color, width_px, interpolation, dash_px)
 					run = PackedVector2Array()
 				continue
 
@@ -201,13 +205,16 @@ class LineRenderer extends Control:
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
 			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
 
-		_finalize_run(run, color, p_width_px, interpolation, dash_px)
+		_finalize_run(run, color, width_px, interpolation, dash_px)
 
 
-	func _draw_series_categorical(p_series_index: int, p_width_px: float) -> void:
+	func _draw_series_categorical(p_series_index: int) -> void:
 		var series_id := _get_line_series_id(p_series_index)
 		var global_series_index := _get_global_series_index(p_series_index)
 		var color := _resolve_series_color(global_series_index)
+		var width_px: float = _line_style.get_series_width_px(global_series_index)
+		if width_px <= 0.0:
+			return
 		var dash_px: int = _line_style.get_series_dash_px(global_series_index)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
@@ -220,7 +227,7 @@ class LineRenderer extends Control:
 			var y_value := _dataset.get_series_y(series_id, cat_idx)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					_finalize_run(run, color, p_width_px, interpolation, dash_px)
+					_finalize_run(run, color, width_px, interpolation, dash_px)
 					run = PackedVector2Array()
 				continue
 
@@ -228,7 +235,7 @@ class LineRenderer extends Control:
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
 			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
 
-		_finalize_run(run, color, p_width_px, interpolation, dash_px)
+		_finalize_run(run, color, width_px, interpolation, dash_px)
 
 
 	func _append_with_interpolation(p_run: PackedVector2Array, p_point: Vector2, p_mode: TauLineConfig.InterpolationMode) -> void:
diff --git a/addons/tau-plot/plot/xy/line/line_style.gd b/addons/tau-plot/plot/xy/line/line_style.gd
index 4bf68f7..2666f6a 100644
--- a/addons/tau-plot/plot/xy/line/line_style.gd
+++ b/addons/tau-plot/plot/xy/line/line_style.gd
@@ -18,8 +18,13 @@ class_name TauLineStyle extends Resource
 #          `has_layout_affecting_change()`.
 ################################################################################################
 
-const DEFAULT_LINE_WIDTH_PX: float = 2.0
-@export var line_width_px: float = DEFAULT_LINE_WIDTH_PX
+## Per-series cycle of line widths in pixels in the normal state. Each entry
+## sets the line width for one series, with the array indexed cyclically by
+## series index using modulo: series [code]i[/code] reads entry
+## [code]i % line_widths_px.size()[/code]. An empty array is treated as all
+## series rendered at [code]2.0[/code] pixels.
+const DEFAULT_LINE_WIDTHS_PX: Array[float] = [2.0]
+@export var line_widths_px: Array[float] = [2.0]
 
 ## Per-series dash length cycle, in pixels. Each entry sets the dash length
 ## for one series, with the array indexed cyclically by series index using
@@ -36,6 +41,18 @@ const DEFAULT_DASH_LENGTHS_PX: Array[int] = [0]
 # Helpers
 ####################################################################################################
 
+## Returns the resolved line width in pixels for the given series index.
+##
+## An empty [member line_widths_px] returns the default
+## [constant DEFAULT_LINE_WIDTHS_PX] entry. The result is clamped to be
+## non-negative.
+func get_series_width_px(p_series_index: int) -> float:
+	if line_widths_px.is_empty():
+		return DEFAULT_LINE_WIDTHS_PX[0]
+	var entry: float = line_widths_px[p_series_index % line_widths_px.size()]
+	return max(entry, 0.0)
+
+
 ## Returns the resolved dash length in pixels for the given series index.
 func get_series_dash_px(p_series_index: int) -> int:
 	if dash_lengths_px.is_empty():
@@ -50,15 +67,14 @@ func get_series_dash_px(p_series_index: int) -> int:
 
 ## Loads properties from the Godot theme attached to [param p_control].
 ##
-## For scalar properties, the non-indexed theme key is fetched first (shared
-## base for all panes), then the indexed key for [param p_pane_index]
-## overwrites it if present.
+## All properties on this resource are per-series arrays. For each, a
+## two-level indexed lookup applies at series granularity:
+##   1. [code]<key>_N[/code] sets the value for series N across all panes.
+##   2. [code]<key>_N_P[/code] overrides series N in pane P only.
 ##
-## For [code]dash_lengths_px[/code], the same convention applies at series
-## granularity:
-##   1. [code]line_dash_px_N[/code] sets the dash length for series N across
-##      all panes.
-##   2. [code]line_dash_px_N_P[/code] overrides series N in pane P only.
+## For [code]line_widths_px[/code] the keys are [code]line_width_px_N[/code]
+## and [code]line_width_px_N_P[/code]. For [code]dash_lengths_px[/code] they
+## are [code]line_dash_px_N[/code] and [code]line_dash_px_N_P[/code].
 ##
 ## This method writes every property unconditionally because it is called on
 ## the resolved instance, not on the user-provided resource.
@@ -67,12 +83,32 @@ func load_from_theme(p_control: Control, p_pane_index: int) -> void:
 		push_error("TauLineStyle.load_from_theme(): control is null")
 		return
 
-	# line_width_px
-	if p_control.has_theme_constant(&"line_width_px"):
-		line_width_px = max(float(p_control.get_theme_constant(&"line_width_px")), 0.0)
-	var indexed_width_key := StringName("line_width_px_%d" % p_pane_index)
-	if p_control.has_theme_constant(indexed_width_key):
-		line_width_px = max(float(p_control.get_theme_constant(indexed_width_key)), 0.0)
+	# line_widths_px: two-level indexed lookup.
+	# Level 1 (global): line_width_px_N
+	var global_widths: Array[float] = []
+	var width_index := 0
+	while true:
+		var key := "line_width_px_%d" % width_index
+		if not p_control.has_theme_constant(key):
+			break
+		global_widths.append(max(float(p_control.get_theme_constant(key)), 0.0))
+		width_index += 1
+
+	if not global_widths.is_empty():
+		line_widths_px = global_widths
+
+	# Level 2 (per-pane): line_width_px_N_P overrides series N in pane P.
+	var pane_width_index := 0
+	while true:
+		var key := "line_width_px_%d_%d" % [pane_width_index, p_pane_index]
+		if not p_control.has_theme_constant(key):
+			break
+		# Grow the array if the per-pane theme defines more width entries than
+		# the global theme (or the default).
+		if pane_width_index >= line_widths_px.size():
+			line_widths_px.resize(pane_width_index + 1)
+		line_widths_px[pane_width_index] = max(float(p_control.get_theme_constant(key)), 0.0)
+		pane_width_index += 1
 
 	# dash_lengths_px: two-level indexed lookup.
 	# Level 1 (global): line_dash_px_N
@@ -113,8 +149,9 @@ func apply_overrides_from(p_user_style: TauLineStyle) -> void:
 	if p_user_style == null:
 		return
 
-	if p_user_style.line_width_px != DEFAULT_LINE_WIDTH_PX:
-		line_width_px = p_user_style.line_width_px
+	# line_widths_px: element-wise comparison against the default array.
+	if _is_line_widths_overridden(p_user_style.line_widths_px):
+		line_widths_px = p_user_style.line_widths_px.duplicate()
 
 	# dash_lengths_px: element-wise comparison against the default array.
 	if _is_dash_lengths_overridden(p_user_style.dash_lengths_px):
@@ -153,8 +190,11 @@ static func resolve(
 func is_equal_to(p_other: TauLineStyle) -> bool:
 	if p_other == null:
 		return false
-	if line_width_px != p_other.line_width_px:
+	if line_widths_px.size() != p_other.line_widths_px.size():
 		return false
+	for i in range(line_widths_px.size()):
+		if line_widths_px[i] != p_other.line_widths_px[i]:
+			return false
 	if dash_lengths_px.size() != p_other.dash_lengths_px.size():
 		return false
 	for i in range(dash_lengths_px.size()):
@@ -173,6 +213,17 @@ func has_layout_affecting_change(p_other: TauLineStyle) -> bool:
 # Private
 ####################################################################################################
 
+## Returns true if [param p_widths] differs from DEFAULT_LINE_WIDTHS_PX using
+## a size + element loop (safest approach for typed arrays in GDScript).
+static func _is_line_widths_overridden(p_widths: Array[float]) -> bool:
+	if p_widths.size() != DEFAULT_LINE_WIDTHS_PX.size():
+		return true
+	for i in range(p_widths.size()):
+		if p_widths[i] != DEFAULT_LINE_WIDTHS_PX[i]:
+			return true
+	return false
+
+
 ## Returns true if [param p_dashes] differs from DEFAULT_DASH_LENGTHS_PX using
 ## a size + element loop (safest approach for typed arrays in GDScript).
 static func _is_dash_lengths_overridden(p_dashes: Array[int]) -> bool:
diff --git a/addons/tau-plot/plot/xy/line/line_visual_attributes.gd b/addons/tau-plot/plot/xy/line/line_visual_attributes.gd
index 83c9efa..edcc860 100644
--- a/addons/tau-plot/plot/xy/line/line_visual_attributes.gd
+++ b/addons/tau-plot/plot/xy/line/line_visual_attributes.gd
@@ -3,5 +3,4 @@ const VisualAttributes = preload("res://addons/tau-plot/plot/xy/visual_attribute
 
 ## Per-sample data-driven visual attribute buffers for LINE overlays.
 class LineVisualAttributes extends VisualAttributes:
-	# TODO: add width_buffer.
 	pass
diff --git a/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd b/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd
index 992b214..fe627af 100644
--- a/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd
+++ b/addons/tau-plot/plot/xy/line/line_visual_callbacks.gd
@@ -3,5 +3,4 @@ const VisualCallbacks = preload("res://addons/tau-plot/plot/xy/visual_callbacks.
 
 ## LINE overlay specific callbacks.
 class LineVisualCallbacks extends VisualCallbacks:
-	# TODO: add width_callback.
 	pass

From f31087a8c1433f79db1d042e6218548dd8675734 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Wed, 29 Apr 2026 12:08:56 +0200
Subject: [PATCH 10/23] Per sample visual styling of LINE

---
 addons/tau-plot/plot/plot.gd                  |   2 +
 addons/tau-plot/plot/xy/line/line_renderer.gd | 193 ++++++++++++---
 .../test_line_visual_attributes_dash_alpha.gd | 190 ++++++++++++++
 ...t_line_visual_attributes_dash_alpha.gd.uid |   1 +
 ...est_line_visual_attributes_dash_alpha.tscn | 190 ++++++++++++++
 .../test_line_visual_attributes_dash_color.gd | 190 ++++++++++++++
 ...t_line_visual_attributes_dash_color.gd.uid |   1 +
 ...est_line_visual_attributes_dash_color.tscn | 190 ++++++++++++++
 ...test_line_visual_attributes_solid_alpha.gd | 189 ++++++++++++++
 ..._line_visual_attributes_solid_alpha.gd.uid |   1 +
 ...st_line_visual_attributes_solid_alpha.tscn | 190 ++++++++++++++
 ...test_line_visual_attributes_solid_color.gd | 189 ++++++++++++++
 ..._line_visual_attributes_solid_color.gd.uid |   1 +
 ...st_line_visual_attributes_solid_color.tscn | 190 ++++++++++++++
 .../test_line_visual_callbacks_dash_alpha.gd  | 233 ++++++++++++++++++
 ...st_line_visual_callbacks_dash_alpha.gd.uid |   1 +
 ...test_line_visual_callbacks_dash_alpha.tscn |  79 ++++++
 .../test_line_visual_callbacks_dash_color.gd  | 231 +++++++++++++++++
 ...st_line_visual_callbacks_dash_color.gd.uid |   1 +
 ...test_line_visual_callbacks_dash_color.tscn |  79 ++++++
 .../test_line_visual_callbacks_solid_alpha.gd | 232 +++++++++++++++++
 ...t_line_visual_callbacks_solid_alpha.gd.uid |   1 +
 ...est_line_visual_callbacks_solid_alpha.tscn |  79 ++++++
 .../test_line_visual_callbacks_solid_color.gd | 230 +++++++++++++++++
 ...t_line_visual_callbacks_solid_color.gd.uid |   1 +
 ...est_line_visual_callbacks_solid_color.tscn |  79 ++++++
 26 files changed, 2923 insertions(+), 40 deletions(-)
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd.uid
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.tscn
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd.uid
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.tscn
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd.uid
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.tscn
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd.uid
 create mode 100644 addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.tscn
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd.uid
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.tscn
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd.uid
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.tscn
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd.uid
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.tscn
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd.uid
 create mode 100644 addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.tscn

diff --git a/addons/tau-plot/plot/plot.gd b/addons/tau-plot/plot/plot.gd
index eca5133..8e0fe5c 100644
--- a/addons/tau-plot/plot/plot.gd
+++ b/addons/tau-plot/plot/plot.gd
@@ -11,10 +11,12 @@ const PaneOverlayType = preload("res://addons/tau-plot/plot/xy/pane_overlay_type
 const VisualAttributes = preload("res://addons/tau-plot/plot/xy/visual_attributes.gd").VisualAttributes
 const BarVisualAttributes := preload("res://addons/tau-plot/plot/xy/bar/bar_visual_attributes.gd").BarVisualAttributes
 const ScatterVisualAttributes = preload("res://addons/tau-plot/plot/xy/scatter/scatter_visual_attributes.gd").ScatterVisualAttributes
+const LineVisualAttributes = preload("res://addons/tau-plot/plot/xy/line/line_visual_attributes.gd").LineVisualAttributes
 
 const VisualCallbacks = preload("res://addons/tau-plot/plot/xy/visual_callbacks.gd").VisualCallbacks
 const BarVisualCallbacks := preload("res://addons/tau-plot/plot/xy/bar/bar_visual_callbacks.gd").BarVisualCallbacks
 const ScatterVisualCallbacks = preload("res://addons/tau-plot/plot/xy/scatter/scatter_visual_callbacks.gd").ScatterVisualCallbacks
+const LineVisualCallbacks = preload("res://addons/tau-plot/plot/xy/line/line_visual_callbacks.gd").LineVisualCallbacks
 
 const SampleHit = preload("res://addons/tau-plot/plot/xy/hover/sample_hit.gd").SampleHit
 
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index b2cc876..f0a1ed8 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -39,18 +39,31 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 #   therefore per series: two series in the same overlay can run on
 #   different paths in the same frame.
 # - Path 1, fast path: resolved per-series dash length is 0. The run is
-#   drawn with a single draw_polyline() call.
+#   drawn with a single draw_polyline_colors() call.
 # - Path 2, dashed batched path: resolved per-series dash length is positive.
 #   Dash phase is precomputed across the full run, the "on" intervals are
 #   collected into a flat segment array, and the run is drawn with a single
-#   draw_multiline() call. The dash phase is continuous across all segments
-#   of the polyline.
+#   draw_multiline_colors() call. The dash phase is continuous across all
+#   segments of the polyline.
+#
+# Per-sample color and alpha resolution:
+# - Color resolution order: LineVisualAttributes.color_buffer, then
+#   LineVisualCallbacks.color_callback, then the per-series color from
+#   TauXYStyle.series_colors.
+# - Alpha resolution order: LineVisualAttributes.alpha_buffer, then
+#   LineVisualCallbacks.alpha_callback, then TauXYStyle.series_alpha.
+# - The resolved alpha overwrites the alpha channel of the resolved color.
+# - Each vertex of the polyline carries its own resolved color. Colors are
+#   linearly interpolated by Godot between consecutive vertices.
+# - Synthetic step-mode intermediate vertices and SMOOTH_MONOTONE sub-samples
+#   are colored consistently with the underlying segment endpoints so the
+#   resulting interpolation matches the chosen interpolation mode.
 #
 # LineValidator is expected to enforce binding-level typing constraints.
 class LineRenderer extends Control:
 	# Number of sub-segments inserted between two consecutive samples by
 	# SMOOTH_MONOTONE. The value balances visual smoothness on a typical
-	# screen against the per-segment cost paid by draw_polyline().
+	# screen against the per-segment cost paid by draw_polyline_colors().
 	const _SMOOTH_SUBDIVISIONS: int = 16
 
 	var _layout: XYLayout = null
@@ -172,7 +185,6 @@ class LineRenderer extends Control:
 	func _draw_series_continuous(p_series_index: int) -> void:
 		var series_id := _get_line_series_id(p_series_index)
 		var global_series_index := _get_global_series_index(p_series_index)
-		var color := _resolve_series_color(global_series_index)
 		var width_px: float = _line_style.get_series_width_px(global_series_index)
 		if width_px <= 0.0:
 			return
@@ -182,6 +194,7 @@ class LineRenderer extends Control:
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
 
 		var run := PackedVector2Array()
+		var run_colors := PackedColorArray()
 
 		var is_shared_x := _dataset.get_mode() == Dataset.Mode.SHARED_X
 		var sample_count := _dataset.get_series_sample_count(series_id)
@@ -190,28 +203,30 @@ class LineRenderer extends Control:
 			var x_value: float = float(_dataset.get_shared_x(i)) if is_shared_x else float(_dataset.get_series_x(series_id, i))
 			if is_nan(x_value) or is_inf(x_value) or not _is_x_value_valid_for_scale(x_value):
 				if not bridge:
-					_finalize_run(run, color, width_px, interpolation, dash_px)
+					_finalize_run(run, run_colors, width_px, interpolation, dash_px)
 					run = PackedVector2Array()
+					run_colors = PackedColorArray()
 				continue
 
 			var y_value := _dataset.get_series_y(series_id, i)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					_finalize_run(run, color, width_px, interpolation, dash_px)
+					_finalize_run(run, run_colors, width_px, interpolation, dash_px)
 					run = PackedVector2Array()
+					run_colors = PackedColorArray()
 				continue
 
 			var x_px := _layout.map_x_to_px(_pane_index, x_value)
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
-			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
+			var sample_color := _resolve_sample_color(p_series_index, i, x_value, y_value)
+			_append_with_interpolation(run, run_colors, _layout.map_point_to_screen(x_px, y_px), sample_color, interpolation)
 
-		_finalize_run(run, color, width_px, interpolation, dash_px)
+		_finalize_run(run, run_colors, width_px, interpolation, dash_px)
 
 
 	func _draw_series_categorical(p_series_index: int) -> void:
 		var series_id := _get_line_series_id(p_series_index)
 		var global_series_index := _get_global_series_index(p_series_index)
-		var color := _resolve_series_color(global_series_index)
 		var width_px: float = _line_style.get_series_width_px(global_series_index)
 		if width_px <= 0.0:
 			return
@@ -220,43 +235,58 @@ class LineRenderer extends Control:
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
 
+		var categories := _layout.domain.x_categories
 		var run := PackedVector2Array()
+		var run_colors := PackedColorArray()
 		var sample_count := _dataset.get_series_sample_count(series_id)
 
 		for cat_idx in range(sample_count):
 			var y_value := _dataset.get_series_y(series_id, cat_idx)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					_finalize_run(run, color, width_px, interpolation, dash_px)
+					_finalize_run(run, run_colors, width_px, interpolation, dash_px)
 					run = PackedVector2Array()
+					run_colors = PackedColorArray()
 				continue
 
 			var x_px := _layout.map_x_category_center_to_px(_pane_index, cat_idx)
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
-			_append_with_interpolation(run, _layout.map_point_to_screen(x_px, y_px), interpolation)
+			var x_value: Variant = categories[cat_idx]
+			var sample_color := _resolve_sample_color(p_series_index, cat_idx, x_value, y_value)
+			_append_with_interpolation(run, run_colors, _layout.map_point_to_screen(x_px, y_px), sample_color, interpolation)
 
-		_finalize_run(run, color, width_px, interpolation, dash_px)
+		_finalize_run(run, run_colors, width_px, interpolation, dash_px)
 
 
-	func _append_with_interpolation(p_run: PackedVector2Array, p_point: Vector2, p_mode: TauLineConfig.InterpolationMode) -> void:
+	# Each appended sample (real or synthetic) gets the new sample's color.
+	# Combined with linear interpolation by draw_polyline_colors() between
+	# consecutive vertices, this places the color transition at the segment
+	# leading INTO the new sample, leaving the staircase tail solid.
+	func _append_with_interpolation(p_run: PackedVector2Array, p_run_colors: PackedColorArray, p_point: Vector2, p_color: Color, p_mode: TauLineConfig.InterpolationMode) -> void:
 		# SMOOTH_MONOTONE buffers raw sample points untouched: cubic resampling
 		# requires the full neighborhood of every sample to compute tangents and
 		# is therefore deferred to _finalize_run().
 		if p_run.size() == 0 or p_mode == TauLineConfig.InterpolationMode.LINEAR or p_mode == TauLineConfig.InterpolationMode.SMOOTH_MONOTONE:
 			p_run.append(p_point)
+			p_run_colors.append(p_color)
 			return
 
 		var last_pt: Vector2 = p_run[p_run.size() - 1]
 		match p_mode:
 			TauLineConfig.InterpolationMode.STEP_BEFORE:
 				p_run.append(Vector2(last_pt.x, p_point.y))
+				p_run_colors.append(p_color)
 			TauLineConfig.InterpolationMode.STEP_AFTER:
 				p_run.append(Vector2(p_point.x, last_pt.y))
+				p_run_colors.append(p_color)
 			TauLineConfig.InterpolationMode.STEP_MIDDLE:
 				var mid_x: float = (last_pt.x + p_point.x) * 0.5
 				p_run.append(Vector2(mid_x, last_pt.y))
+				p_run_colors.append(p_color)
 				p_run.append(Vector2(mid_x, p_point.y))
+				p_run_colors.append(p_color)
 		p_run.append(p_point)
+		p_run_colors.append(p_color)
 
 
 	# Draw the polyline for one buffered run.
@@ -264,39 +294,50 @@ class LineRenderer extends Control:
 	# For SMOOTH_MONOTONE the run is first replaced by its Fritsch-Carlson piecewise cubic resampling.
 	# Runs of fewer than two points are silently dropped.
 	#
-	# When p_dash_px is 0, the polyline is emitted via path 1 (draw_polyline).
+	# When p_dash_px is 0, the polyline is emitted via path 1 (draw_polyline_colors).
 	# Otherwise it is emitted via path 2: dash phase is precomputed across the
 	# whole polyline and the resulting "on" intervals are flushed in a single
-	# draw_multiline() call. p_dash_px is the resolved per-series dash length
-	# obtained from TauLineStyle.get_series_dash_px().
-	func _finalize_run(p_run: PackedVector2Array, p_color: Color, p_width_px: float, p_mode: TauLineConfig.InterpolationMode, p_dash_px: int) -> void:
+	# draw_multiline_colors() call. p_dash_px is the resolved per-series dash
+	# length obtained from TauLineStyle.get_series_dash_px().
+	func _finalize_run(p_run: PackedVector2Array, p_run_colors: PackedColorArray, p_width_px: float, p_mode: TauLineConfig.InterpolationMode, p_dash_px: int) -> void:
 		var polyline: PackedVector2Array = p_run
+		var polyline_colors: PackedColorArray = p_run_colors
 		if p_mode == TauLineConfig.InterpolationMode.SMOOTH_MONOTONE and p_run.size() > 2:
-			polyline = _resample_smooth_monotone(p_run)
+			var resampled := _resample_smooth_monotone(p_run, p_run_colors)
+			polyline = resampled[0]
+			polyline_colors = resampled[1]
 		if polyline.size() < 2:
 			return
 
 		var dash_px: int = max(p_dash_px, 0)
 		if dash_px <= 0:
-			draw_polyline(polyline, p_color, p_width_px)
+			draw_polyline_colors(polyline, polyline_colors, p_width_px)
 		else:
-			_draw_dashed_polyline(polyline, p_color, p_width_px, float(dash_px))
+			_draw_dashed_polyline(polyline, polyline_colors, p_width_px, float(dash_px))
 
 
 	# Builds the flat segment array of "on" dash intervals along p_polyline and
-	# emits it with a single draw_multiline() call. The dash period is
+	# emits it with a single draw_multiline_colors() call. The dash period is
 	# 2 * p_dash_px (one "on" length followed by one "off" length of equal
 	# size). Dash phase is tracked as a single scalar that advances along the
 	# polyline arc length, so the pattern is continuous across consecutive
 	# segments and does not reset at sample positions.
 	#
+	# draw_multiline_colors takes one solid color per emitted segment (a pair
+	# of points). Each "on" interval gets the color of its midpoint along the
+	# enclosing polyline segment, computed by linear interpolation between the
+	# two flanking polyline-vertex colors. For typical dash sizes this is a
+	# good approximation of the per-vertex color gradient produced by the
+	# undashed path.
+	#
 	# Degenerate segments (zero length) are skipped: they cannot carry any
 	# dash and do not advance the phase.
-	func _draw_dashed_polyline(p_polyline: PackedVector2Array, p_color: Color, p_width_px: float, p_dash_px: float) -> void:
+	func _draw_dashed_polyline(p_polyline: PackedVector2Array, p_polyline_colors: PackedColorArray, p_width_px: float, p_dash_px: float) -> void:
 		var period: float = p_dash_px * 2.0
 		var n := p_polyline.size()
 		var phase: float = 0.0
 		var segments := PackedVector2Array()
+		var segment_colors := PackedColorArray()
 
 		for i in range(n - 1):
 			var seg_start: Vector2 = p_polyline[i]
@@ -307,6 +348,8 @@ class LineRenderer extends Control:
 				continue
 
 			var seg_dir: Vector2 = seg_vec / seg_len
+			var col_start: Color = p_polyline_colors[i]
+			var col_end: Color = p_polyline_colors[i + 1]
 
 			# Position along the current segment, in pixels from seg_start.
 			# Phase 0..p_dash_px is "on", p_dash_px..period is "off".
@@ -319,6 +362,8 @@ class LineRenderer extends Control:
 					var on_end: float = min(pos + remaining_on, seg_len)
 					segments.append(seg_start + seg_dir * pos)
 					segments.append(seg_start + seg_dir * on_end)
+					var midpoint_t: float = ((pos + on_end) * 0.5) / seg_len
+					segment_colors.append(col_start.lerp(col_end, midpoint_t))
 					var consumed: float = on_end - pos
 					phase += consumed
 					pos = on_end
@@ -334,7 +379,7 @@ class LineRenderer extends Control:
 					phase -= period
 
 		if segments.size() >= 2:
-			draw_multiline(segments, p_color, p_width_px)
+			draw_multiline_colors(segments, segment_colors, p_width_px)
 
 	####################################################################################################
 	# Smooth-monotone (Fritsch-Carlson) resampling
@@ -342,67 +387,90 @@ class LineRenderer extends Control:
 
 	# Builds the Fritsch-Carlson piecewise cubic Hermite curve through p_points
 	# and returns it sampled at _SMOOTH_SUBDIVISIONS sub-segments per input
-	# segment. Operates in screen space (the input is already in pixels), which
-	# keeps the curve visually smooth regardless of axis scale.
+	# segment, paired with a colors array sampled in lock-step. Operates in
+	# screen space (the input is already in pixels), which keeps the curve
+	# visually smooth regardless of axis scale.
 	#
 	# The algorithm requires strictly monotonic X. The expected case is
 	# monotonically increasing screen X, but a user-inverted X axis produces
 	# monotonically decreasing screen X. Both directions are accepted: the
 	# input is processed internally on a strictly increasing X copy and the
 	# output is reversed back when needed. Consecutive points sharing the same
-	# screen X are dropped since the secant slope is undefined at h = 0.
+	# screen X are dropped since the secant slope is undefined at h = 0. The
+	# matching color entries are dropped at the same indices.
 	# Inputs that are not monotonic in either direction fall back to the raw
 	# polyline for that run and emit a one-shot warning.
-	func _resample_smooth_monotone(p_points: PackedVector2Array) -> PackedVector2Array:
+	#
+	# Sub-sample colors are linearly interpolated between the two flanking
+	# kept-sample colors so that the visual color gradient matches what
+	# draw_polyline_colors would produce on a LINEAR polyline through the
+	# same kept samples.
+	#
+	# Returns [points: PackedVector2Array, colors: PackedColorArray].
+	func _resample_smooth_monotone(p_points: PackedVector2Array, p_colors: PackedColorArray) -> Array:
 		var direction := _detect_monotonic_x_direction(p_points)
 		if direction == 0:
 			if not _smooth_non_monotonic_warned:
 				push_warning("LineRenderer: SMOOTH_MONOTONE received samples whose screen X is not monotonic. Falling back to a straight polyline for the affected run. Use LINEAR interpolation if your data does not have a monotonic X parameter.")
 				_smooth_non_monotonic_warned = true
-			return p_points
+			return [p_points, p_colors]
 
 		var ascending: bool = direction > 0
 
 		# Build strictly increasing X arrays, dropping flat-X duplicates.
+		# Colors are kept in lock-step with the kept points.
 		var xs := PackedFloat32Array()
 		var ys := PackedFloat32Array()
+		var cs := PackedColorArray()
 		var input_count := p_points.size()
 		if ascending:
 			xs.append(p_points[0].x)
 			ys.append(p_points[0].y)
+			cs.append(p_colors[0])
 			for i in range(1, input_count):
 				if p_points[i].x > xs[xs.size() - 1]:
 					xs.append(p_points[i].x)
 					ys.append(p_points[i].y)
+					cs.append(p_colors[i])
 		else:
 			xs.append(p_points[input_count - 1].x)
 			ys.append(p_points[input_count - 1].y)
+			cs.append(p_colors[input_count - 1])
 			for i in range(input_count - 2, -1, -1):
 				if p_points[i].x > xs[xs.size() - 1]:
 					xs.append(p_points[i].x)
 					ys.append(p_points[i].y)
+					cs.append(p_colors[i])
 
 		var n := xs.size()
 		if n < 2:
 			# All inputs collapsed to a single screen X. Nothing to draw.
-			return PackedVector2Array()
+			return [PackedVector2Array(), PackedColorArray()]
 		if n == 2:
 			# Two distinct X values produce a straight line through Hermite
 			# with both tangents equal to the secant slope. Short-circuit.
 			var trivial := PackedVector2Array()
+			var trivial_colors := PackedColorArray()
 			trivial.append(Vector2(xs[0], ys[0]))
 			trivial.append(Vector2(xs[1], ys[1]))
+			trivial_colors.append(cs[0])
+			trivial_colors.append(cs[1])
 			if not ascending:
 				trivial.reverse()
-			return trivial
+				trivial_colors.reverse()
+			return [trivial, trivial_colors]
 
 		var tangents := _fritsch_carlson_tangents(xs, ys)
 
 		var out := PackedVector2Array()
-		# Pre-size the output for speed: n-1 segments times subdivisions plus
+		var out_colors := PackedColorArray()
+		# Pre-size the outputs for speed: n-1 segments times subdivisions plus
 		# the very first sample.
-		out.resize(1 + (n - 1) * _SMOOTH_SUBDIVISIONS)
+		var out_size: int = 1 + (n - 1) * _SMOOTH_SUBDIVISIONS
+		out.resize(out_size)
+		out_colors.resize(out_size)
 		out[0] = Vector2(xs[0], ys[0])
+		out_colors[0] = cs[0]
 
 		var write_index: int = 1
 		var inv_subs: float = 1.0 / float(_SMOOTH_SUBDIVISIONS)
@@ -414,6 +482,8 @@ class LineRenderer extends Control:
 			var h: float = x1 - x0
 			var m0: float = tangents[k]
 			var m1: float = tangents[k + 1]
+			var c0: Color = cs[k]
+			var c1: Color = cs[k + 1]
 
 			# Sub-points at t = 1/N, 2/N, ..., 1. The endpoint t=1 is the next
 			# sample, included here so the next segment begins at t=1/N.
@@ -428,11 +498,13 @@ class LineRenderer extends Control:
 				var x: float = x0 + t * h
 				var y: float = h00 * y0 + h10 * h * m0 + h01 * y1 + h11 * h * m1
 				out[write_index] = Vector2(x, y)
+				out_colors[write_index] = c0.lerp(c1, t)
 				write_index += 1
 
 		if not ascending:
 			out.reverse()
-		return out
+			out_colors.reverse()
+		return [out, out_colors]
 
 
 	# Returns +1 if screen X is strictly monotonically increasing across the
@@ -555,14 +627,55 @@ class LineRenderer extends Control:
 
 
 	####################################################################################################
-	# Color resolution
+	# Per-sample color and alpha resolution
 	####################################################################################################
 
-	# TODO: fully implement _resolve_series_color
-	func _resolve_series_color(p_global_series_index: int) -> Color:
-		var color := _xy_style.get_series_color(p_global_series_index)
-		color.a = clampf(_xy_style.series_alpha, 0.0, 1.0)
-		return color
+	# Combined per-sample color resolution. The alpha resolved by
+	# _resolve_sample_alpha overwrites the alpha channel of the color resolved
+	# by _resolve_sample_color_only.
+	func _resolve_sample_color(p_series_index: int, p_sample_index: int, p_x_value: Variant, p_y_value: float) -> Color:
+		var base := _resolve_sample_color_only(p_series_index, p_sample_index, p_x_value, p_y_value)
+		var alpha := _resolve_sample_alpha(p_series_index, p_sample_index, p_x_value, p_y_value)
+		base.a = clampf(alpha, 0.0, 1.0)
+		return base
+
+
+	func _resolve_sample_color_only(p_series_index: int, p_sample_index: int, p_x_value: Variant, p_y_value: float) -> Color:
+		# Per-sample override from LineVisualAttributes.color_buffer.
+		if p_series_index >= 0 and p_series_index < _visual_attributes.size():
+			var color_buffer: VisualAttributes.ColorBuffer = _visual_attributes[p_series_index].color_buffer
+			if color_buffer != null and p_sample_index >= 0 and p_sample_index < color_buffer.size():
+				var c := color_buffer.get_value(p_sample_index)
+				if c != VisualAttributes.ColorBuffer.NO_COLOR:
+					return c
+
+		var global_series_index := _get_global_series_index(p_series_index)
+
+		# Per-sample override from LineVisualCallbacks.color_callback.
+		var vc := _line_config.line_visual_callbacks
+		if vc != null and vc.color_callback.is_valid():
+			return vc.color_callback.call(global_series_index, p_sample_index, p_x_value, p_y_value)
+
+		return _xy_style.get_series_color(global_series_index)
+
+
+	func _resolve_sample_alpha(p_series_index: int, p_sample_index: int, p_x_value: Variant, p_y_value: float) -> float:
+		# Per-sample override from LineVisualAttributes.alpha_buffer.
+		if p_series_index >= 0 and p_series_index < _visual_attributes.size():
+			var alpha_buffer: VisualAttributes.AlphaBuffer = _visual_attributes[p_series_index].alpha_buffer
+			if alpha_buffer != null and p_sample_index >= 0 and p_sample_index < alpha_buffer.size():
+				var a := alpha_buffer.get_value(p_sample_index)
+				if a >= 0.0:
+					return a
+
+		# Per-sample override from LineVisualCallbacks.alpha_callback.
+		var vc := _line_config.line_visual_callbacks
+		if vc != null and vc.alpha_callback.is_valid():
+			var a: float = vc.alpha_callback.call(_get_global_series_index(p_series_index), p_sample_index, p_x_value, p_y_value)
+			if a >= 0.0:
+				return a
+
+		return _xy_style.series_alpha
 
 
 	####################################################################################################
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd
new file mode 100644
index 0000000..a043626
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd
@@ -0,0 +1,190 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+	_setup_test_9()
+	_setup_test_10()
+	_setup_test_11()
+	_setup_test_12()
+	_setup_test_13()
+	_setup_test_14()
+	_setup_test_15()
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode, p_num_alphas: int) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0, 75.0, 60.0, 45.0, 25.0, 0.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 10
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.style.dash_lengths_px = [8]
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+	var alpha_buffer_a = TauPlot.VisualAttributes.AlphaBuffer.new(x.size())
+	var alpha_values := PackedFloat32Array([
+		0.00,
+		0.08,
+		0.16,
+		0.25,
+		0.33,
+		0.45,
+		0.57,
+		0.65,
+		0.8,
+		1.0,
+		])
+	alpha_values.resize(p_num_alphas)
+	alpha_buffer_a.append_values(alpha_values)
+	var visual_attributes_a := TauPlot.LineVisualAttributes.new()
+	visual_attributes_a.alpha_buffer = alpha_buffer_a
+	sb_a.visual_attributes = visual_attributes_a
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR] 10 alphas", TauLineConfig.InterpolationMode.LINEAR, 10)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_shared_x_continuous_plot(%TestPlot2, "[LINEAR] 5 alphas", TauLineConfig.InterpolationMode.LINEAR, 5)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "[LINEAR] 1 alpha", TauLineConfig.InterpolationMode.LINEAR, 1)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_BEFORE] 10 alphas", TauLineConfig.InterpolationMode.STEP_BEFORE, 10)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "[STEP_BEFORE] 5 alphas", TauLineConfig.InterpolationMode.STEP_BEFORE, 5)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_shared_x_continuous_plot(%TestPlot6, "[STEP_BEFORE] 1 alpha", TauLineConfig.InterpolationMode.STEP_BEFORE, 1)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "[STEP_MIDDLE] 10 alphas", TauLineConfig.InterpolationMode.STEP_MIDDLE, 10)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_shared_x_continuous_plot(%TestPlot8, "[STEP_MIDDLE] 5 alphas", TauLineConfig.InterpolationMode.STEP_MIDDLE, 5)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_continuous_plot(%TestPlot9, "[STEP_MIDDLE] 1 alpha", TauLineConfig.InterpolationMode.STEP_MIDDLE, 1)
+
+####################################################################################################
+# Test 10
+####################################################################################################
+
+func _setup_test_10() -> void:
+	make_shared_x_continuous_plot(%TestPlot10, "[STEP_AFTER] 10 alphas", TauLineConfig.InterpolationMode.STEP_AFTER, 10)
+
+####################################################################################################
+# Test 11
+####################################################################################################
+
+func _setup_test_11() -> void:
+	make_shared_x_continuous_plot(%TestPlot11, "[STEP_AFTER] 5 alphas", TauLineConfig.InterpolationMode.STEP_AFTER, 5)
+
+####################################################################################################
+# Test 12
+####################################################################################################
+
+func _setup_test_12() -> void:
+	make_shared_x_continuous_plot(%TestPlot12, "[STEP_AFTER] 1 alpha", TauLineConfig.InterpolationMode.STEP_AFTER, 1)
+
+####################################################################################################
+# Test 13
+####################################################################################################
+
+func _setup_test_13() -> void:
+	make_shared_x_continuous_plot(%TestPlot13, "[SMOOTH_MONOTONE] 10 alphas", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 10)
+
+####################################################################################################
+# Test 14
+####################################################################################################
+
+func _setup_test_14() -> void:
+	make_shared_x_continuous_plot(%TestPlot14, "[SMOOTH_MONOTONE] 5 alphas", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 5)
+
+####################################################################################################
+# Test 15
+####################################################################################################
+
+func _setup_test_15() -> void:
+	make_shared_x_continuous_plot(%TestPlot15, "[SMOOTH_MONOTONE] 1 alpha", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 1)
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd.uid b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd.uid
new file mode 100644
index 0000000..947d65c
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd.uid
@@ -0,0 +1 @@
+uid://vi4vdovvscly
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.tscn b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.tscn
new file mode 100644
index 0000000..911e9f1
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.tscn
@@ -0,0 +1,190 @@
+[gd_scene load_steps=3 format=3 uid="uid://by44kyvc18a1g"]
+
+[ext_resource type="Script" uid="uid://vi4vdovvscly" path="res://addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd" id="1_lv2ey"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_touct"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_lv2ey")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test LINE visual attributes (alpha only on dashed lines)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[LINEAR] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[LINEAR] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[LINEAR] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[STEP_BEFORE] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[STEP_BEFORE] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[STEP_BEFORE] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[STEP_MIDDLE] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[STEP_MIDDLE] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[STEP_MIDDLE] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot10" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[STEP_AFTER] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot11" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[STEP_AFTER] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot12" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[STEP_AFTER] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot13" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[SMOOTH_MONOTONE] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot14" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[SMOOTH_MONOTONE] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot15" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_touct")
+title = "[SMOOTH_MONOTONE] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd
new file mode 100644
index 0000000..4910753
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd
@@ -0,0 +1,190 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+	_setup_test_9()
+	_setup_test_10()
+	_setup_test_11()
+	_setup_test_12()
+	_setup_test_13()
+	_setup_test_14()
+	_setup_test_15()
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode, p_num_colors: int) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0, 75.0, 60.0, 45.0, 25.0, 0.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 10
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.style.dash_lengths_px = [8]
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+	var color_buffer_a = TauPlot.VisualAttributes.ColorBuffer.new(x.size())
+	var color_values := PackedColorArray([
+		Color(0.069, 0.391, 0.338, 1.0),
+		Color(0.069, 0.429, 0.508, 1.0),
+		Color(0.197, 0.328, 0.575, 1.0),
+		Color(0.358, 0.3, 0.475, 1.0),
+		Color(0.516, 0.211, 0.37, 1.0),
+		Color(0.507, 0.066, 0.284, 1.0),
+		Color(0.529, 0.232, 0.197, 1.0),
+		Color(0.49, 0.408, 0.116, 1.0),
+		Color(0.309, 0.473, 0.129, 1.0),
+		Color(0.01, 0.487, 0.249, 1.0),
+		])
+	color_values.resize(p_num_colors)
+	color_buffer_a.append_values(color_values)
+	var visual_attributes_a := TauPlot.LineVisualAttributes.new()
+	visual_attributes_a.color_buffer = color_buffer_a
+	sb_a.visual_attributes = visual_attributes_a
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR] 10 colors", TauLineConfig.InterpolationMode.LINEAR, 10)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_shared_x_continuous_plot(%TestPlot2, "[LINEAR] 5 colors", TauLineConfig.InterpolationMode.LINEAR, 5)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "[LINEAR] 1 color", TauLineConfig.InterpolationMode.LINEAR, 1)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_BEFORE] 10 colors", TauLineConfig.InterpolationMode.STEP_BEFORE, 10)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "[STEP_BEFORE] 5 colors", TauLineConfig.InterpolationMode.STEP_BEFORE, 5)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_shared_x_continuous_plot(%TestPlot6, "[STEP_BEFORE] 1 color", TauLineConfig.InterpolationMode.STEP_BEFORE, 1)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "[STEP_MIDDLE] 10 colors", TauLineConfig.InterpolationMode.STEP_MIDDLE, 10)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_shared_x_continuous_plot(%TestPlot8, "[STEP_MIDDLE] 5 colors", TauLineConfig.InterpolationMode.STEP_MIDDLE, 5)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_continuous_plot(%TestPlot9, "[STEP_MIDDLE] 1 color", TauLineConfig.InterpolationMode.STEP_MIDDLE, 1)
+
+####################################################################################################
+# Test 10
+####################################################################################################
+
+func _setup_test_10() -> void:
+	make_shared_x_continuous_plot(%TestPlot10, "[STEP_AFTER] 10 colors", TauLineConfig.InterpolationMode.STEP_AFTER, 10)
+
+####################################################################################################
+# Test 11
+####################################################################################################
+
+func _setup_test_11() -> void:
+	make_shared_x_continuous_plot(%TestPlot11, "[STEP_AFTER] 5 colors", TauLineConfig.InterpolationMode.STEP_AFTER, 5)
+
+####################################################################################################
+# Test 12
+####################################################################################################
+
+func _setup_test_12() -> void:
+	make_shared_x_continuous_plot(%TestPlot12, "[STEP_AFTER] 1 color", TauLineConfig.InterpolationMode.STEP_AFTER, 1)
+
+####################################################################################################
+# Test 13
+####################################################################################################
+
+func _setup_test_13() -> void:
+	make_shared_x_continuous_plot(%TestPlot13, "[SMOOTH_MONOTONE] 10 colors", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 10)
+
+####################################################################################################
+# Test 14
+####################################################################################################
+
+func _setup_test_14() -> void:
+	make_shared_x_continuous_plot(%TestPlot14, "[SMOOTH_MONOTONE] 5 colors", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 5)
+
+####################################################################################################
+# Test 15
+####################################################################################################
+
+func _setup_test_15() -> void:
+	make_shared_x_continuous_plot(%TestPlot15, "[SMOOTH_MONOTONE] 1 color", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 1)
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd.uid b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd.uid
new file mode 100644
index 0000000..a5c6807
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd.uid
@@ -0,0 +1 @@
+uid://5dh41vpm1xd3
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.tscn b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.tscn
new file mode 100644
index 0000000..c77ef9a
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.tscn
@@ -0,0 +1,190 @@
+[gd_scene load_steps=3 format=3 uid="uid://bburlly6t4pae"]
+
+[ext_resource type="Script" uid="uid://5dh41vpm1xd3" path="res://addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd" id="1_yv5ay"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_le50r"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_yv5ay")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test LINE visual attributes (color only on dashed lines)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[LINEAR] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[LINEAR] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[LINEAR] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[STEP_BEFORE] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[STEP_BEFORE] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[STEP_BEFORE] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[STEP_MIDDLE] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[STEP_MIDDLE] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[STEP_MIDDLE] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot10" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[STEP_AFTER] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot11" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[STEP_AFTER] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot12" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[STEP_AFTER] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot13" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[SMOOTH_MONOTONE] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot14" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[SMOOTH_MONOTONE] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot15" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_le50r")
+title = "[SMOOTH_MONOTONE] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd
new file mode 100644
index 0000000..f010578
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd
@@ -0,0 +1,189 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+	_setup_test_9()
+	_setup_test_10()
+	_setup_test_11()
+	_setup_test_12()
+	_setup_test_13()
+	_setup_test_14()
+	_setup_test_15()
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode, p_num_alphas: int) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0, 75.0, 60.0, 45.0, 25.0, 0.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 10
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+	var alpha_buffer_a = TauPlot.VisualAttributes.AlphaBuffer.new(x.size())
+	var alpha_values := PackedFloat32Array([
+		0.00,
+		0.08,
+		0.16,
+		0.25,
+		0.33,
+		0.45,
+		0.57,
+		0.65,
+		0.8,
+		1.0,
+		])
+	alpha_values.resize(p_num_alphas)
+	alpha_buffer_a.append_values(alpha_values)
+	var visual_attributes_a := TauPlot.LineVisualAttributes.new()
+	visual_attributes_a.alpha_buffer = alpha_buffer_a
+	sb_a.visual_attributes = visual_attributes_a
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR] 10 alphas", TauLineConfig.InterpolationMode.LINEAR, 10)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_shared_x_continuous_plot(%TestPlot2, "[LINEAR] 5 alphas", TauLineConfig.InterpolationMode.LINEAR, 5)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "[LINEAR] 1 alpha", TauLineConfig.InterpolationMode.LINEAR, 1)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_BEFORE] 10 alphas", TauLineConfig.InterpolationMode.STEP_BEFORE, 10)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "[STEP_BEFORE] 5 alphas", TauLineConfig.InterpolationMode.STEP_BEFORE, 5)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_shared_x_continuous_plot(%TestPlot6, "[STEP_BEFORE] 1 alpha", TauLineConfig.InterpolationMode.STEP_BEFORE, 1)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "[STEP_MIDDLE] 10 alphas", TauLineConfig.InterpolationMode.STEP_MIDDLE, 10)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_shared_x_continuous_plot(%TestPlot8, "[STEP_MIDDLE] 5 alphas", TauLineConfig.InterpolationMode.STEP_MIDDLE, 5)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_continuous_plot(%TestPlot9, "[STEP_MIDDLE] 1 alpha", TauLineConfig.InterpolationMode.STEP_MIDDLE, 1)
+
+####################################################################################################
+# Test 10
+####################################################################################################
+
+func _setup_test_10() -> void:
+	make_shared_x_continuous_plot(%TestPlot10, "[STEP_AFTER] 10 alphas", TauLineConfig.InterpolationMode.STEP_AFTER, 10)
+
+####################################################################################################
+# Test 11
+####################################################################################################
+
+func _setup_test_11() -> void:
+	make_shared_x_continuous_plot(%TestPlot11, "[STEP_AFTER] 5 alphas", TauLineConfig.InterpolationMode.STEP_AFTER, 5)
+
+####################################################################################################
+# Test 12
+####################################################################################################
+
+func _setup_test_12() -> void:
+	make_shared_x_continuous_plot(%TestPlot12, "[STEP_AFTER] 1 alpha", TauLineConfig.InterpolationMode.STEP_AFTER, 1)
+
+####################################################################################################
+# Test 13
+####################################################################################################
+
+func _setup_test_13() -> void:
+	make_shared_x_continuous_plot(%TestPlot13, "[SMOOTH_MONOTONE] 10 alphas", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 10)
+
+####################################################################################################
+# Test 14
+####################################################################################################
+
+func _setup_test_14() -> void:
+	make_shared_x_continuous_plot(%TestPlot14, "[SMOOTH_MONOTONE] 5 alphas", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 5)
+
+####################################################################################################
+# Test 15
+####################################################################################################
+
+func _setup_test_15() -> void:
+	make_shared_x_continuous_plot(%TestPlot15, "[SMOOTH_MONOTONE] 1 alpha", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 1)
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd.uid b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd.uid
new file mode 100644
index 0000000..4e7b51b
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd.uid
@@ -0,0 +1 @@
+uid://vro08bntv7uo
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.tscn b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.tscn
new file mode 100644
index 0000000..45a5473
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.tscn
@@ -0,0 +1,190 @@
+[gd_scene load_steps=3 format=3 uid="uid://bx0xwt3nrm2tb"]
+
+[ext_resource type="Script" uid="uid://vro08bntv7uo" path="res://addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd" id="1_u76at"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_hy82u"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_u76at")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test LINE visual attributes (alpha only on solid lines)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[LINEAR] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[LINEAR] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[LINEAR] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[STEP_BEFORE] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[STEP_BEFORE] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[STEP_BEFORE] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[STEP_MIDDLE] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[STEP_MIDDLE] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[STEP_MIDDLE] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot10" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[STEP_AFTER] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot11" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[STEP_AFTER] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot12" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[STEP_AFTER] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot13" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[SMOOTH_MONOTONE] 10 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot14" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[SMOOTH_MONOTONE] 5 alphas"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot15" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_hy82u")
+title = "[SMOOTH_MONOTONE] 1 alpha"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd
new file mode 100644
index 0000000..d170609
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd
@@ -0,0 +1,189 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+	_setup_test_9()
+	_setup_test_10()
+	_setup_test_11()
+	_setup_test_12()
+	_setup_test_13()
+	_setup_test_14()
+	_setup_test_15()
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode, p_num_colors: int) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0, 75.0, 60.0, 45.0, 25.0, 0.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 10
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+	var color_buffer_a = TauPlot.VisualAttributes.ColorBuffer.new(x.size())
+	var color_values := PackedColorArray([
+		Color(0.069, 0.391, 0.338, 1.0),
+		Color(0.069, 0.429, 0.508, 1.0),
+		Color(0.197, 0.328, 0.575, 1.0),
+		Color(0.358, 0.3, 0.475, 1.0),
+		Color(0.516, 0.211, 0.37, 1.0),
+		Color(0.507, 0.066, 0.284, 1.0),
+		Color(0.529, 0.232, 0.197, 1.0),
+		Color(0.49, 0.408, 0.116, 1.0),
+		Color(0.309, 0.473, 0.129, 1.0),
+		Color(0.01, 0.487, 0.249, 1.0),
+		])
+	color_values.resize(p_num_colors)
+	color_buffer_a.append_values(color_values)
+	var visual_attributes_a := TauPlot.LineVisualAttributes.new()
+	visual_attributes_a.color_buffer = color_buffer_a
+	sb_a.visual_attributes = visual_attributes_a
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR] 10 colors", TauLineConfig.InterpolationMode.LINEAR, 10)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_shared_x_continuous_plot(%TestPlot2, "[LINEAR] 5 colors", TauLineConfig.InterpolationMode.LINEAR, 5)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "[LINEAR] 1 color", TauLineConfig.InterpolationMode.LINEAR, 1)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_BEFORE] 10 colors", TauLineConfig.InterpolationMode.STEP_BEFORE, 10)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "[STEP_BEFORE] 5 colors", TauLineConfig.InterpolationMode.STEP_BEFORE, 5)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_shared_x_continuous_plot(%TestPlot6, "[STEP_BEFORE] 1 color", TauLineConfig.InterpolationMode.STEP_BEFORE, 1)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "[STEP_MIDDLE] 10 colors", TauLineConfig.InterpolationMode.STEP_MIDDLE, 10)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_shared_x_continuous_plot(%TestPlot8, "[STEP_MIDDLE] 5 colors", TauLineConfig.InterpolationMode.STEP_MIDDLE, 5)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_continuous_plot(%TestPlot9, "[STEP_MIDDLE] 1 color", TauLineConfig.InterpolationMode.STEP_MIDDLE, 1)
+
+####################################################################################################
+# Test 10
+####################################################################################################
+
+func _setup_test_10() -> void:
+	make_shared_x_continuous_plot(%TestPlot10, "[STEP_AFTER] 10 colors", TauLineConfig.InterpolationMode.STEP_AFTER, 10)
+
+####################################################################################################
+# Test 11
+####################################################################################################
+
+func _setup_test_11() -> void:
+	make_shared_x_continuous_plot(%TestPlot11, "[STEP_AFTER] 5 colors", TauLineConfig.InterpolationMode.STEP_AFTER, 5)
+
+####################################################################################################
+# Test 12
+####################################################################################################
+
+func _setup_test_12() -> void:
+	make_shared_x_continuous_plot(%TestPlot12, "[STEP_AFTER] 1 color", TauLineConfig.InterpolationMode.STEP_AFTER, 1)
+
+####################################################################################################
+# Test 13
+####################################################################################################
+
+func _setup_test_13() -> void:
+	make_shared_x_continuous_plot(%TestPlot13, "[SMOOTH_MONOTONE] 10 colors", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 10)
+
+####################################################################################################
+# Test 14
+####################################################################################################
+
+func _setup_test_14() -> void:
+	make_shared_x_continuous_plot(%TestPlot14, "[SMOOTH_MONOTONE] 5 colors", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 5)
+
+####################################################################################################
+# Test 15
+####################################################################################################
+
+func _setup_test_15() -> void:
+	make_shared_x_continuous_plot(%TestPlot15, "[SMOOTH_MONOTONE] 1 color", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE, 1)
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd.uid b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd.uid
new file mode 100644
index 0000000..1104420
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd.uid
@@ -0,0 +1 @@
+uid://c78fi08wv7vqd
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.tscn b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.tscn
new file mode 100644
index 0000000..1d39731
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.tscn
@@ -0,0 +1,190 @@
+[gd_scene load_steps=3 format=3 uid="uid://djun6fo6ivusk"]
+
+[ext_resource type="Script" uid="uid://c78fi08wv7vqd" path="res://addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd" id="1_7vjol"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_lc0kd"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_7vjol")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test LINE visual attributes (color only on solid lines)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[LINEAR] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[LINEAR] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[LINEAR] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[STEP_BEFORE] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[STEP_BEFORE] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[STEP_BEFORE] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[STEP_MIDDLE] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[STEP_MIDDLE] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[STEP_MIDDLE] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot10" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[STEP_AFTER] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot11" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[STEP_AFTER] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot12" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[STEP_AFTER] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot13" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[SMOOTH_MONOTONE] 10 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot14" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[SMOOTH_MONOTONE] 5 colors"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot15" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_lc0kd")
+title = "[SMOOTH_MONOTONE] 1 color"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd
new file mode 100644
index 0000000..71c983d
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd
@@ -0,0 +1,233 @@
+@tool
+extends Control
+
+class Spectrum extends RefCounted:
+
+	const ATTACK_HZ: float = 18.0
+	const RELEASE_HZ: float = 6.0
+	const ENERGY_DECAY_HZ: float = 10.0
+	const HIT_RATE: float = 5.5
+	const HIT_STRENGTH: float = 1.2
+	const BREATH: float = 0.08
+
+	var values: Array[float] = []
+	var energy: Array[float] = []
+	var phase: Array[float] = []
+
+	func _init(p_band_count: int = 16) -> void:
+		values.resize(p_band_count)
+		energy.resize(p_band_count)
+		phase.resize(p_band_count)
+
+		for i in p_band_count:
+			values[i] = randf()
+			energy[i] = 0.0
+			phase[i] = randf() * TAU
+
+	func step(delta: float) -> void:
+		for i in values.size():
+			_step_band(i, delta)
+
+	func _step_band(i: int, delta: float) -> void:
+		# 1) transient impulses (Poisson-ish)
+		if randf() < HIT_RATE * delta:
+			var impulse := pow(randf(), 3.0) * HIT_STRENGTH
+			energy[i] += impulse
+
+		# 2) excitation decay
+		energy[i] *= exp(-ENERGY_DECAY_HZ * delta)
+
+		# 3) slow breathing motion
+		phase[i] += (2.0 + 3.0 * randf()) * delta
+		var slow_noise := sin(phase[i]) * BREATH
+
+		var target := energy[i] + slow_noise
+
+		# 4) fast attack, slow release
+		if target > values[i]:
+			values[i] += (target - values[i]) * (1.0 - exp(-ATTACK_HZ * delta))
+		else:
+			values[i] += (target - values[i]) * (1.0 - exp(-RELEASE_HZ * delta))
+
+var _t: float = 0.0
+
+var _datasets: Array[TauPlot.Dataset] = []
+var _state: Array[Dictionary] = []
+
+var _spectrum: Spectrum = null
+var _spectrum_2: Spectrum = null
+
+var _gradient: Gradient = null
+
+func _ready() -> void:
+	_t = 0.0
+	_datasets.clear()
+	_state.clear()
+	_spectrum = Spectrum.new(10)
+
+	_gradient = Gradient.new()
+	_gradient.offsets = PackedFloat32Array([
+		0.0,
+		0.25,
+		0.5,
+		0.75,
+		1.0
+	])
+	_gradient.colors = PackedColorArray([
+		Color("bd0034ff"),
+		Color("cc4219ff"),
+		Color("c97010ff"),
+		Color("b4aa00ff"),
+		Color("439800ff"),
+	])
+
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+
+
+func _process(delta: float) -> void:
+	_t += delta
+
+	_spectrum.step(delta)
+
+	_step_test_1(delta)
+	_step_test_2(delta)
+	_step_test_3(delta)
+	_step_test_4(delta)
+	_step_test_5(delta)
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0, 75.0, 60.0, 45.0, 25.0, 0.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+	_datasets.append(dataset)
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 10
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+	y_axis.range_override_enabled = true
+	y_axis.min_override = -Spectrum.BREATH
+	y_axis.max_override = 1.0
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.style.dash_lengths_px = [8]
+	var visual_callbacks := TauPlot.LineVisualCallbacks.new()
+	visual_callbacks.alpha_callback = Callable(func(series_index: int, sample_index: int, x_value: Variant, y_value: float) -> float:
+		const k := 1.6
+		var  y := clampf(y_value, 0.0, 1.0)
+		return (k + 1.0) * y / (1.0 + k * y)
+	)
+	line_config.visual_callbacks = visual_callbacks
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR]", TauLineConfig.InterpolationMode.LINEAR)
+
+
+func _step_test_1(delta: float) -> void:
+	var dataset := _datasets[0]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_shared_x_continuous_plot(%TestPlot2, "[STEP_BEFORE]", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+
+func _step_test_2(delta: float) -> void:
+	var dataset := _datasets[1]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "[STEP_MIDDLE]", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+
+func _step_test_3(delta: float) -> void:
+	var dataset := _datasets[2]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_AFTER]", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+
+func _step_test_4(delta: float) -> void:
+	var dataset := _datasets[3]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "[SMOOTH_MONOTONE]", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+
+func _step_test_5(delta: float) -> void:
+	var dataset := _datasets[4]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd.uid b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd.uid
new file mode 100644
index 0000000..e96042a
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd.uid
@@ -0,0 +1 @@
+uid://d1ehkjmoa0dhx
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.tscn b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.tscn
new file mode 100644
index 0000000..7dc3e02
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.tscn
@@ -0,0 +1,79 @@
+[gd_scene load_steps=3 format=3 uid="uid://bnf1v6jsjtk6l"]
+
+[ext_resource type="Script" uid="uid://d1ehkjmoa0dhx" path="res://addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd" id="1_w8xoc"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_wvy6q"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_w8xoc")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test LINE visual callbacks (alpha only on dashed lines)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_wvy6q")
+title = "[LINEAR]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_wvy6q")
+title = "[STEP_BEFORE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_wvy6q")
+title = "[STEP_MIDDLE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_wvy6q")
+title = "[STEP_AFTER]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_wvy6q")
+title = "[SMOOTH_MONOTONE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd
new file mode 100644
index 0000000..21af4aa
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd
@@ -0,0 +1,231 @@
+@tool
+extends Control
+
+class Spectrum extends RefCounted:
+
+	const ATTACK_HZ: float = 18.0
+	const RELEASE_HZ: float = 6.0
+	const ENERGY_DECAY_HZ: float = 10.0
+	const HIT_RATE: float = 5.5
+	const HIT_STRENGTH: float = 1.2
+	const BREATH: float = 0.08
+
+	var values: Array[float] = []
+	var energy: Array[float] = []
+	var phase: Array[float] = []
+
+	func _init(p_band_count: int = 16) -> void:
+		values.resize(p_band_count)
+		energy.resize(p_band_count)
+		phase.resize(p_band_count)
+
+		for i in p_band_count:
+			values[i] = randf()
+			energy[i] = 0.0
+			phase[i] = randf() * TAU
+
+	func step(delta: float) -> void:
+		for i in values.size():
+			_step_band(i, delta)
+
+	func _step_band(i: int, delta: float) -> void:
+		# 1) transient impulses (Poisson-ish)
+		if randf() < HIT_RATE * delta:
+			var impulse := pow(randf(), 3.0) * HIT_STRENGTH
+			energy[i] += impulse
+
+		# 2) excitation decay
+		energy[i] *= exp(-ENERGY_DECAY_HZ * delta)
+
+		# 3) slow breathing motion
+		phase[i] += (2.0 + 3.0 * randf()) * delta
+		var slow_noise := sin(phase[i]) * BREATH
+
+		var target := energy[i] + slow_noise
+
+		# 4) fast attack, slow release
+		if target > values[i]:
+			values[i] += (target - values[i]) * (1.0 - exp(-ATTACK_HZ * delta))
+		else:
+			values[i] += (target - values[i]) * (1.0 - exp(-RELEASE_HZ * delta))
+
+var _t: float = 0.0
+
+var _datasets: Array[TauPlot.Dataset] = []
+var _state: Array[Dictionary] = []
+
+var _spectrum: Spectrum = null
+var _spectrum_2: Spectrum = null
+
+var _gradient: Gradient = null
+
+func _ready() -> void:
+	_t = 0.0
+	_datasets.clear()
+	_state.clear()
+	_spectrum = Spectrum.new(10)
+
+	_gradient = Gradient.new()
+	_gradient.offsets = PackedFloat32Array([
+		0.0,
+		0.25,
+		0.5,
+		0.75,
+		1.0
+	])
+	_gradient.colors = PackedColorArray([
+		Color("bd0034ff"),
+		Color("cc4219ff"),
+		Color("c97010ff"),
+		Color("b4aa00ff"),
+		Color("439800ff"),
+	])
+
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+
+
+func _process(delta: float) -> void:
+	_t += delta
+
+	_spectrum.step(delta)
+
+	_step_test_1(delta)
+	_step_test_2(delta)
+	_step_test_3(delta)
+	_step_test_4(delta)
+	_step_test_5(delta)
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0, 75.0, 60.0, 45.0, 25.0, 0.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+	_datasets.append(dataset)
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 10
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+	y_axis.range_override_enabled = true
+	y_axis.min_override = -Spectrum.BREATH
+	y_axis.max_override = 1.0
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.style.dash_lengths_px = [8]
+	var visual_callbacks := TauPlot.LineVisualCallbacks.new()
+	visual_callbacks.color_callback = Callable(func(series_index: int, sample_index: int, x_value: Variant, y_value: float) -> Color:
+		return _gradient.sample(clampf(1.0 - y_value, 0.0, 1.0))
+	)
+	line_config.visual_callbacks = visual_callbacks
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR]", TauLineConfig.InterpolationMode.LINEAR)
+
+
+func _step_test_1(delta: float) -> void:
+	var dataset := _datasets[0]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_shared_x_continuous_plot(%TestPlot2, "[STEP_BEFORE]", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+
+func _step_test_2(delta: float) -> void:
+	var dataset := _datasets[1]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "[STEP_MIDDLE]", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+
+func _step_test_3(delta: float) -> void:
+	var dataset := _datasets[2]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_AFTER]", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+
+func _step_test_4(delta: float) -> void:
+	var dataset := _datasets[3]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "[SMOOTH_MONOTONE]", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+
+func _step_test_5(delta: float) -> void:
+	var dataset := _datasets[4]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd.uid b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd.uid
new file mode 100644
index 0000000..948d88c
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd.uid
@@ -0,0 +1 @@
+uid://tgw2e12ovgd
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.tscn b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.tscn
new file mode 100644
index 0000000..41f03e1
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.tscn
@@ -0,0 +1,79 @@
+[gd_scene load_steps=3 format=3 uid="uid://6t7qku0by8cw"]
+
+[ext_resource type="Script" uid="uid://tgw2e12ovgd" path="res://addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd" id="1_mx55d"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_0c0l8"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_mx55d")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test LINE visual callbacks (color only on dashed lines)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_0c0l8")
+title = "[LINEAR]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_0c0l8")
+title = "[STEP_BEFORE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_0c0l8")
+title = "[STEP_MIDDLE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_0c0l8")
+title = "[STEP_AFTER]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_0c0l8")
+title = "[SMOOTH_MONOTONE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd
new file mode 100644
index 0000000..9e722f2
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd
@@ -0,0 +1,232 @@
+@tool
+extends Control
+
+class Spectrum extends RefCounted:
+
+	const ATTACK_HZ: float = 18.0
+	const RELEASE_HZ: float = 6.0
+	const ENERGY_DECAY_HZ: float = 10.0
+	const HIT_RATE: float = 5.5
+	const HIT_STRENGTH: float = 1.2
+	const BREATH: float = 0.08
+
+	var values: Array[float] = []
+	var energy: Array[float] = []
+	var phase: Array[float] = []
+
+	func _init(p_band_count: int = 16) -> void:
+		values.resize(p_band_count)
+		energy.resize(p_band_count)
+		phase.resize(p_band_count)
+
+		for i in p_band_count:
+			values[i] = randf()
+			energy[i] = 0.0
+			phase[i] = randf() * TAU
+
+	func step(delta: float) -> void:
+		for i in values.size():
+			_step_band(i, delta)
+
+	func _step_band(i: int, delta: float) -> void:
+		# 1) transient impulses (Poisson-ish)
+		if randf() < HIT_RATE * delta:
+			var impulse := pow(randf(), 3.0) * HIT_STRENGTH
+			energy[i] += impulse
+
+		# 2) excitation decay
+		energy[i] *= exp(-ENERGY_DECAY_HZ * delta)
+
+		# 3) slow breathing motion
+		phase[i] += (2.0 + 3.0 * randf()) * delta
+		var slow_noise := sin(phase[i]) * BREATH
+
+		var target := energy[i] + slow_noise
+
+		# 4) fast attack, slow release
+		if target > values[i]:
+			values[i] += (target - values[i]) * (1.0 - exp(-ATTACK_HZ * delta))
+		else:
+			values[i] += (target - values[i]) * (1.0 - exp(-RELEASE_HZ * delta))
+
+var _t: float = 0.0
+
+var _datasets: Array[TauPlot.Dataset] = []
+var _state: Array[Dictionary] = []
+
+var _spectrum: Spectrum = null
+var _spectrum_2: Spectrum = null
+
+var _gradient: Gradient = null
+
+func _ready() -> void:
+	_t = 0.0
+	_datasets.clear()
+	_state.clear()
+	_spectrum = Spectrum.new(10)
+
+	_gradient = Gradient.new()
+	_gradient.offsets = PackedFloat32Array([
+		0.0,
+		0.25,
+		0.5,
+		0.75,
+		1.0
+	])
+	_gradient.colors = PackedColorArray([
+		Color("bd0034ff"),
+		Color("cc4219ff"),
+		Color("c97010ff"),
+		Color("b4aa00ff"),
+		Color("439800ff"),
+	])
+
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+
+
+func _process(delta: float) -> void:
+	_t += delta
+
+	_spectrum.step(delta)
+
+	_step_test_1(delta)
+	_step_test_2(delta)
+	_step_test_3(delta)
+	_step_test_4(delta)
+	_step_test_5(delta)
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0, 75.0, 60.0, 45.0, 25.0, 0.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+	_datasets.append(dataset)
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 10
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+	y_axis.range_override_enabled = true
+	y_axis.min_override = -Spectrum.BREATH
+	y_axis.max_override = 1.0
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	var visual_callbacks := TauPlot.LineVisualCallbacks.new()
+	visual_callbacks.alpha_callback = Callable(func(series_index: int, sample_index: int, x_value: Variant, y_value: float) -> float:
+		const k := 1.6
+		var  y := clampf(y_value, 0.0, 1.0)
+		return (k + 1.0) * y / (1.0 + k * y)
+	)
+	line_config.visual_callbacks = visual_callbacks
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR]", TauLineConfig.InterpolationMode.LINEAR)
+
+
+func _step_test_1(delta: float) -> void:
+	var dataset := _datasets[0]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_shared_x_continuous_plot(%TestPlot2, "[STEP_BEFORE]", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+
+func _step_test_2(delta: float) -> void:
+	var dataset := _datasets[1]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "[STEP_MIDDLE]", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+
+func _step_test_3(delta: float) -> void:
+	var dataset := _datasets[2]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_AFTER]", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+
+func _step_test_4(delta: float) -> void:
+	var dataset := _datasets[3]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "[SMOOTH_MONOTONE]", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+
+func _step_test_5(delta: float) -> void:
+	var dataset := _datasets[4]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd.uid b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd.uid
new file mode 100644
index 0000000..546db18
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd.uid
@@ -0,0 +1 @@
+uid://byunb5b3q5f0n
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.tscn b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.tscn
new file mode 100644
index 0000000..4363503
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.tscn
@@ -0,0 +1,79 @@
+[gd_scene load_steps=3 format=3 uid="uid://8juhu4rtvj3p"]
+
+[ext_resource type="Script" uid="uid://byunb5b3q5f0n" path="res://addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd" id="1_8ct1l"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_ronnj"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_8ct1l")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test LINE visual callbacks (alpha only on solid lines)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_ronnj")
+title = "[LINEAR]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_ronnj")
+title = "[STEP_BEFORE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_ronnj")
+title = "[STEP_MIDDLE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_ronnj")
+title = "[STEP_AFTER]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_ronnj")
+title = "[SMOOTH_MONOTONE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd
new file mode 100644
index 0000000..e748d01
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd
@@ -0,0 +1,230 @@
+@tool
+extends Control
+
+class Spectrum extends RefCounted:
+
+	const ATTACK_HZ: float = 18.0
+	const RELEASE_HZ: float = 6.0
+	const ENERGY_DECAY_HZ: float = 10.0
+	const HIT_RATE: float = 5.5
+	const HIT_STRENGTH: float = 1.2
+	const BREATH: float = 0.08
+
+	var values: Array[float] = []
+	var energy: Array[float] = []
+	var phase: Array[float] = []
+
+	func _init(p_band_count: int = 16) -> void:
+		values.resize(p_band_count)
+		energy.resize(p_band_count)
+		phase.resize(p_band_count)
+
+		for i in p_band_count:
+			values[i] = randf()
+			energy[i] = 0.0
+			phase[i] = randf() * TAU
+
+	func step(delta: float) -> void:
+		for i in values.size():
+			_step_band(i, delta)
+
+	func _step_band(i: int, delta: float) -> void:
+		# 1) transient impulses (Poisson-ish)
+		if randf() < HIT_RATE * delta:
+			var impulse := pow(randf(), 3.0) * HIT_STRENGTH
+			energy[i] += impulse
+
+		# 2) excitation decay
+		energy[i] *= exp(-ENERGY_DECAY_HZ * delta)
+
+		# 3) slow breathing motion
+		phase[i] += (2.0 + 3.0 * randf()) * delta
+		var slow_noise := sin(phase[i]) * BREATH
+
+		var target := energy[i] + slow_noise
+
+		# 4) fast attack, slow release
+		if target > values[i]:
+			values[i] += (target - values[i]) * (1.0 - exp(-ATTACK_HZ * delta))
+		else:
+			values[i] += (target - values[i]) * (1.0 - exp(-RELEASE_HZ * delta))
+
+var _t: float = 0.0
+
+var _datasets: Array[TauPlot.Dataset] = []
+var _state: Array[Dictionary] = []
+
+var _spectrum: Spectrum = null
+var _spectrum_2: Spectrum = null
+
+var _gradient: Gradient = null
+
+func _ready() -> void:
+	_t = 0.0
+	_datasets.clear()
+	_state.clear()
+	_spectrum = Spectrum.new(10)
+
+	_gradient = Gradient.new()
+	_gradient.offsets = PackedFloat32Array([
+		0.0,
+		0.25,
+		0.5,
+		0.75,
+		1.0
+	])
+	_gradient.colors = PackedColorArray([
+		Color("bd0034ff"),
+		Color("cc4219ff"),
+		Color("c97010ff"),
+		Color("b4aa00ff"),
+		Color("439800ff"),
+	])
+
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+
+
+func _process(delta: float) -> void:
+	_t += delta
+
+	_spectrum.step(delta)
+
+	_step_test_1(delta)
+	_step_test_2(delta)
+	_step_test_3(delta)
+	_step_test_4(delta)
+	_step_test_5(delta)
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 65.0, 70.0, 75.0, 60.0, 45.0, 25.0, 0.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a])
+	_datasets.append(dataset)
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.tick_count_preferred = 10
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+	y_axis.range_override_enabled = true
+	y_axis.min_override = -Spectrum.BREATH
+	y_axis.max_override = 1.0
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	var visual_callbacks := TauPlot.LineVisualCallbacks.new()
+	visual_callbacks.color_callback = Callable(func(series_index: int, sample_index: int, x_value: Variant, y_value: float) -> Color:
+		return _gradient.sample(clampf(1.0 - y_value, 0.0, 1.0))
+	)
+	line_config.visual_callbacks = visual_callbacks
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR]", TauLineConfig.InterpolationMode.LINEAR)
+
+
+func _step_test_1(delta: float) -> void:
+	var dataset := _datasets[0]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_shared_x_continuous_plot(%TestPlot2, "[STEP_BEFORE]", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+
+func _step_test_2(delta: float) -> void:
+	var dataset := _datasets[1]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_continuous_plot(%TestPlot3, "[STEP_MIDDLE]", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+
+func _step_test_3(delta: float) -> void:
+	var dataset := _datasets[2]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_AFTER]", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+
+func _step_test_4(delta: float) -> void:
+	var dataset := _datasets[3]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_shared_x_continuous_plot(%TestPlot5, "[SMOOTH_MONOTONE]", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+
+func _step_test_5(delta: float) -> void:
+	var dataset := _datasets[4]
+	dataset.begin_batch()
+	for b in range(dataset.get_shared_capacity()):
+		dataset.set_series_y(dataset.get_series_id_by_index(0), b, _spectrum.values[b])
+	dataset.end_batch()
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd.uid b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd.uid
new file mode 100644
index 0000000..1c0aa55
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd.uid
@@ -0,0 +1 @@
+uid://bnuv0vxxw14ea
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.tscn b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.tscn
new file mode 100644
index 0000000..2a93ff8
--- /dev/null
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.tscn
@@ -0,0 +1,79 @@
+[gd_scene load_steps=3 format=3 uid="uid://7nurv5el8l02"]
+
+[ext_resource type="Script" uid="uid://bnuv0vxxw14ea" path="res://addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd" id="1_lev7j"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_xbeyi"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_lev7j")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test LINE visual callbacks (color only on solid lines)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xbeyi")
+title = "[LINEAR]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xbeyi")
+title = "[STEP_BEFORE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xbeyi")
+title = "[STEP_MIDDLE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xbeyi")
+title = "[STEP_AFTER]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xbeyi")
+title = "[SMOOTH_MONOTONE]"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"

From e5433b05451253c7e3d7a4d321fe9236f89ff2b0 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Fri, 1 May 2026 12:25:19 +0200
Subject: [PATCH 11/23] Hover lines initial version

---
 .../plot/xy/hover/hover_controller.gd         |  69 ++--
 .../tau-plot/plot/xy/line/line_hit_record.gd  |  18 +
 .../plot/xy/line/line_hit_record.gd.uid       |   1 +
 .../tau-plot/plot/xy/line/line_hit_tester.gd  | 165 ++++++++
 .../plot/xy/line/line_hit_tester.gd.uid       |   1 +
 addons/tau-plot/plot/xy/line/line_renderer.gd | 363 ++++++++++++++++--
 addons/tau-plot/plot/xy/line/line_style.gd    |  79 +++-
 addons/tau-plot/plot/xy/xy_plot.gd            |   8 +
 8 files changed, 644 insertions(+), 60 deletions(-)
 create mode 100644 addons/tau-plot/plot/xy/line/line_hit_record.gd
 create mode 100644 addons/tau-plot/plot/xy/line/line_hit_record.gd.uid
 create mode 100644 addons/tau-plot/plot/xy/line/line_hit_tester.gd
 create mode 100644 addons/tau-plot/plot/xy/line/line_hit_tester.gd.uid

diff --git a/addons/tau-plot/plot/xy/hover/hover_controller.gd b/addons/tau-plot/plot/xy/hover/hover_controller.gd
index f4f0772..c1e6986 100644
--- a/addons/tau-plot/plot/xy/hover/hover_controller.gd
+++ b/addons/tau-plot/plot/xy/hover/hover_controller.gd
@@ -139,7 +139,7 @@ class HoverController extends RefCounted:
 		_current_pane = -1
 		_hide_transient_tooltip()
 		_hide_all_crosshairs()
-		_clear_highlight_state_on_renderers()
+		_clear_renderers_hover_state()
 		# Also hide pinned tooltip since screen positions are stale.
 		if not _pinned_hits.is_empty():
 			_pinned_hits.clear()
@@ -193,7 +193,7 @@ class HoverController extends RefCounted:
 			return
 
 		if p_event is InputEventMouseMotion:
-			_process_motion(p_pane_index, p_local_pos)
+			_process_mouse_motion(p_pane_index, p_local_pos)
 
 		elif p_event is InputEventMouseButton:
 			var mb := p_event as InputEventMouseButton
@@ -210,7 +210,7 @@ class HoverController extends RefCounted:
 
 
 	## Processes mouse motion: runs hit testing and emits hover signals.
-	func _process_motion(p_pane_index: int, p_local_pos: Vector2) -> void:
+	func _process_mouse_motion(p_pane_index: int, p_local_pos: Vector2) -> void:
 		# Convert pane-local position to plot-local for tooltip positioning.
 		_last_mouse_pos = _pane_to_plot_local(p_pane_index, p_local_pos)
 
@@ -228,7 +228,7 @@ class HoverController extends RefCounted:
 				_current_pane = -1
 				_hide_transient_tooltip()
 				_hide_all_crosshairs()
-				_clear_highlight_state_on_renderers()
+				_clear_renderers_hover_state()
 				_plot.sample_hover_exited.emit()
 			return
 
@@ -236,7 +236,7 @@ class HoverController extends RefCounted:
 		_current_pane = p_pane_index
 		_show_transient_tooltip(hits, p_pane_index)
 		_show_crosshairs(hits, p_pane_index, p_local_pos)
-		_push_highlight_state_to_renderers(hits)
+		_update_renderers_hover_state(hits)
 		_plot.sample_hovered.emit(hits)
 
 
@@ -282,15 +282,14 @@ class HoverController extends RefCounted:
 		for hit_tester: OverlayHitTester in hit_testers:
 			if not hit_tester.is_hoverable():
 				continue
+
 			var preferred: int = hit_tester.get_preferred_hover_mode()
 			if agreed_mode == -1:
 				agreed_mode = preferred
 			elif agreed_mode != preferred:
 				return HoverMode.NEAREST
 
-		if agreed_mode == -1:
-			return HoverMode.NEAREST
-		return agreed_mode as HoverMode
+		return agreed_mode as HoverMode if agreed_mode != -1 else HoverMode.NEAREST
 
 
 	####################################################################
@@ -534,32 +533,41 @@ class HoverController extends RefCounted:
 		return _resolve_mode(p_pane_index) == HoverMode.X_ALIGNED
 
 
-	## Pushes highlight state to all bar and scatter renderers based on the
-	## current set of hits. Each renderer receives set_hover_state with the
-	## hit that belongs to it (matched by pane index and overlay type). If a
-	## renderer has no hit, it still receives p_active = true so that the
-	## color callback dims its samples, but p_series_id = -1 so no sample
-	## gets hovered-state style properties.
+	## Update the renderers hover state based on the current set of hits.
+	## Each renderer receives set_hover_state with the hit that belongs to it
+	## (matched by pane index and overlay type). If a renderer has no hit, it
+	## still receives p_active = true so that the color callback dims its samples,
+	## but p_series_id = -1 so no sample gets hovered-state style properties.
 	##
 	## For GROUPED bars in X_ALIGNED mode, the entire group at the hovered
 	## sample index is highlighted together via set_hover_state_group.
-	func _push_highlight_state_to_renderers(p_hits: Array[SampleHit]) -> void:
+	##
+	## For line overlays in X_ALIGNED mode, the closest hit to the pointer
+	## (smallest distance_px) is selected as the visually emphasized sample
+	## in each pane: hovering "the line at column X" picks the single line
+	## whose curve passes nearest to the cursor for the thicker emphasis,
+	## while the tooltip still lists all line series at that X.
+	func _update_renderers_hover_state(p_hits: Array[SampleHit]) -> void:
 		if not _is_highlight_enabled():
-			_clear_highlight_state_on_renderers()
+			_clear_renderers_hover_state()
 			return
 
 		var highlight_cb: Callable = _get_hover_highlight_callback()
 
 		# Build a lookup from pane_index to the best hit for that pane, per
-		# overlay type. Selection priority:
+		# overlay type. Selection priority for bars and scatter:
 		#   1. Hits where contains_pointer is true (cursor inside the visual
 		#      element). Among those, pick the one with the smallest distance_px.
 		#   2. If no hit contains the pointer, no sample is highlighted for that
 		#      overlay (series_id = -1). The tooltip still shows all hits, but
 		#      the visual highlight is suppressed because the cursor is not
 		#      physically inside any element.
+		# Lines are not bounded by a visual element along the y axis in
+		# X_ALIGNED mode, so they pick the smallest distance_px regardless of
+		# contains_pointer: the closest curve to the cursor wins the emphasis.
 		var bar_hits_by_pane: Dictionary[int, SampleHit] = {}
 		var scatter_hits_by_pane: Dictionary[int, SampleHit] = {}
+		var line_hits_by_pane: Dictionary[int, SampleHit] = {}
 
 		# Also track the sample_index for group highlighting (any bar hit,
 		# even without contains_pointer, tells us the hovered category).
@@ -580,8 +588,9 @@ class HoverController extends RefCounted:
 					if existing == null or hit.distance_px < existing.distance_px:
 						scatter_hits_by_pane[hit.pane_index] = hit
 			elif hit.overlay_type == PaneOverlayType.LINE:
-				# TODO: categorize line hits once line hover is wired.
-				pass
+				var existing: SampleHit = line_hits_by_pane.get(hit.pane_index)
+				if existing == null or hit.distance_px < existing.distance_px:
+					line_hits_by_pane[hit.pane_index] = hit
 
 		for pane_index: int in range(_bar_renderers.size()):
 			var renderer: BarRenderer = _bar_renderers[pane_index]
@@ -612,10 +621,20 @@ class HoverController extends RefCounted:
 			else:
 				renderer.set_hover_state(true, -1, -1, highlight_cb)
 
+		for pane_index: int in range(_line_renderers.size()):
+			var renderer: LineRenderer = _line_renderers[pane_index]
+			if renderer == null:
+				continue  # Pane has no line overlay.
+			var hit: SampleHit = line_hits_by_pane.get(pane_index)
+			if hit != null:
+				renderer.set_hover_state(true, hit.series_id, hit.sample_index, highlight_cb)
+			else:
+				renderer.set_hover_state(true, -1, -1, highlight_cb)
+
 
-	## Clears highlight state on all bar and scatter renderers, returning
-	## them to normal (non-highlighted) drawing.
-	func _clear_highlight_state_on_renderers() -> void:
+	## Clears hover state on all bar, scatter, and line renderers,
+	## returning them to normal (non-highlighted) drawing.
+	func _clear_renderers_hover_state() -> void:
 		for pane_index: int in range(_bar_renderers.size()):
 			var renderer: BarRenderer = _bar_renderers[pane_index]
 			if renderer == null:
@@ -628,6 +647,12 @@ class HoverController extends RefCounted:
 				continue  # Pane has no scatter overlay.
 			renderer.set_hover_state(false, -1, -1, Callable())
 
+		for pane_index: int in range(_line_renderers.size()):
+			var renderer: LineRenderer = _line_renderers[pane_index]
+			if renderer == null:
+				continue  # Pane has no line overlay.
+			renderer.set_hover_state(false, -1, -1, Callable())
+
 
 	####################################################################
 	# Private: coordinate conversion
diff --git a/addons/tau-plot/plot/xy/line/line_hit_record.gd b/addons/tau-plot/plot/xy/line/line_hit_record.gd
new file mode 100644
index 0000000..52f610b
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_hit_record.gd
@@ -0,0 +1,18 @@
+## Snapshot of one real sample drawn onto a line polyline, in pane-local
+## screen coordinates. One record per dataset sample, sub-samples
+## are not recorded.
+class LineHitRecord extends RefCounted:
+	## Dataset series id.
+	var series_id: int
+
+	## Sample index within the series.
+	var sample_index: int
+
+	## Float for continuous x, String for categorical.
+	var x_value: Variant
+
+	## Plotted y value.
+	var y_value: float
+
+	## Real sample position in pane-local screen coordinates.
+	var screen_position: Vector2
diff --git a/addons/tau-plot/plot/xy/line/line_hit_record.gd.uid b/addons/tau-plot/plot/xy/line/line_hit_record.gd.uid
new file mode 100644
index 0000000..2a8a16a
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_hit_record.gd.uid
@@ -0,0 +1 @@
+uid://ba1k0sngdojnn
diff --git a/addons/tau-plot/plot/xy/line/line_hit_tester.gd b/addons/tau-plot/plot/xy/line/line_hit_tester.gd
new file mode 100644
index 0000000..df8be79
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_hit_tester.gd
@@ -0,0 +1,165 @@
+const Dataset := preload("res://addons/tau-plot/model/dataset.gd").Dataset
+const XYLayout := preload("res://addons/tau-plot/plot/xy/xy_layout.gd").XYLayout
+const SampleHit = preload("res://addons/tau-plot/plot/xy/hover/sample_hit.gd").SampleHit
+const HoverMode = preload("res://addons/tau-plot/plot/xy/hover/hover_config.gd").HoverMode
+const OverlayHitTester = preload("res://addons/tau-plot/plot/xy/hover/overlay_hit_tester.gd").OverlayHitTester
+const PaneOverlayType = preload("res://addons/tau-plot/plot/xy/pane_overlay_type.gd").PaneOverlayType
+const LineRenderer := preload("res://addons/tau-plot/plot/xy/line/line_renderer.gd").LineRenderer
+const LineHitRecord := preload("res://addons/tau-plot/plot/xy/line/line_hit_record.gd").LineHitRecord
+
+
+## Hit tester for the line overlay. Reads the renderer's LineHitRecord cache
+## so the hit geometry cannot drift from the painted geometry.
+##
+## In NEAREST mode, performs a brute-force linear scan over all records and
+## returns the closest sample within hover_max_distance_px.
+## In X_ALIGNED mode, collects all samples whose x position (categorical
+## index or continuous value) matches the target.
+##
+## Line overlays prefer X_ALIGNED in TauHoverConfig.HoverMode.AUTO because
+## line charts are typically read along the x axis.
+class LineHitTester extends OverlayHitTester:
+	var _pane_index: int
+	var _line_config: TauLineConfig
+	var _line_renderer: LineRenderer
+	var _dataset: Dataset
+	var _layout: XYLayout
+
+
+	func _init(
+			p_pane_index: int,
+			p_line_config: TauLineConfig,
+			p_line_renderer: LineRenderer,
+			p_dataset: Dataset,
+			p_layout: XYLayout) -> void:
+		_pane_index = p_pane_index
+		_line_config = p_line_config
+		_line_renderer = p_line_renderer
+		_dataset = p_dataset
+		_layout = p_layout
+
+
+	func is_hoverable() -> bool:
+		return _line_config.hoverable
+
+
+	func get_preferred_hover_mode() -> HoverMode:
+		return HoverMode.X_ALIGNED
+
+
+	####################################################################
+	# NEAREST mode
+	####################################################################
+
+	## Brute-force linear scan. Returns the closest record within
+	## hover_max_distance_px, or null.
+	func hit_test_nearest(p_local_pos: Vector2) -> SampleHit:
+		var max_dist: float = float(_line_config.hover_max_distance_px)
+		var max_dist_sq: float = max_dist * max_dist
+		var best_record: LineHitRecord = null
+		var best_dist_sq: float = INF
+
+		for record: LineHitRecord in _line_renderer.get_hit_records():
+			var dx: float = p_local_pos.x - record.screen_position.x
+			var dy: float = p_local_pos.y - record.screen_position.y
+			var dist_sq: float = dx * dx + dy * dy
+			if dist_sq < best_dist_sq and dist_sq <= max_dist_sq:
+				best_dist_sq = dist_sq
+				best_record = record
+
+		if best_record == null:
+			return null
+		return _build_hit(best_record, sqrt(best_dist_sq), true)
+
+
+	####################################################################
+	# X_ALIGNED mode
+	####################################################################
+
+	func collect_hits_at_category(p_category_index: int, p_x_value: String, p_local_pos: Vector2) -> Array[SampleHit]:
+		var hits: Array[SampleHit] = []
+		var max_dist: float = float(_line_config.hover_max_distance_px)
+
+		for record: LineHitRecord in _line_renderer.get_hit_records():
+			if record.sample_index != p_category_index:
+				continue
+			var dx: float = p_local_pos.x - record.screen_position.x
+			var dy: float = p_local_pos.y - record.screen_position.y
+			var dist: float = sqrt(dx * dx + dy * dy)
+			# Categorical hits override the cached x_value with the resolved
+			# category label so the hit reads consistently with bars and
+			# scatter at the same X.
+			var hit := _build_hit(record, dist, dist <= max_dist)
+			hit.x_value = p_x_value
+			hits.append(hit)
+
+		return hits
+
+
+	func collect_hits_at_continuous_x(p_x_value: float, p_local_pos: Vector2) -> Array[SampleHit]:
+		var max_dist_x: float = float(_line_config.hover_max_distance_px)
+		var x_is_horizontal: bool = _layout._x_is_horizontal
+		var target_x_px: float = _layout.map_x_to_px(_pane_index, p_x_value)
+		var hits: Array[SampleHit] = []
+
+		for record: LineHitRecord in _line_renderer.get_hit_records():
+			var sample_x_px: float = record.screen_position.x if x_is_horizontal else record.screen_position.y
+			var x_dist: float = absf(sample_x_px - target_x_px)
+			if x_dist > max_dist_x:
+				continue
+
+			# Reject records whose x value drifts numerically from the target.
+			# The pixel gate above is necessary but not sufficient for sparse
+			# datasets where two distinct samples can map to nearby pixels.
+			if record.x_value is float:
+				if not OverlayHitTester.x_values_match(record.x_value, p_x_value):
+					continue
+
+			var dx: float = p_local_pos.x - record.screen_position.x
+			var dy: float = p_local_pos.y - record.screen_position.y
+			var dist: float = sqrt(dx * dx + dy * dy)
+			hits.append(_build_hit(record, dist, dist <= max_dist_x))
+
+		return hits
+
+
+	## Returns the nearest x pixel position and data value across all
+	## records, or an empty dictionary when no records exist.
+	func find_nearest_x(p_along_x_px: float) -> Dictionary:
+		var x_is_horizontal: bool = _layout._x_is_horizontal
+		var best_px: float = INF
+		var best_val: float = 0.0
+		var found: bool = false
+
+		for record: LineHitRecord in _line_renderer.get_hit_records():
+			var x_px: float = record.screen_position.x if x_is_horizontal else record.screen_position.y
+			if absf(p_along_x_px - x_px) < absf(p_along_x_px - best_px):
+				best_px = x_px
+				if record.x_value is float:
+					best_val = record.x_value
+				else:
+					best_val = float(record.x_value)
+				found = true
+
+		if not found:
+			return {}
+		return { "x_px": best_px, "x_value": best_val }
+
+
+	####################################################################
+	# Private
+	####################################################################
+
+	func _build_hit(p_record: LineHitRecord, p_distance: float, p_contains: bool) -> SampleHit:
+		var hit := SampleHit.new()
+		hit.series_id = p_record.series_id
+		hit.series_name = _dataset.get_series_name(p_record.series_id)
+		hit.sample_index = p_record.sample_index
+		hit.x_value = p_record.x_value
+		hit.y_value = p_record.y_value
+		hit.screen_position = p_record.screen_position
+		hit.pane_index = _pane_index
+		hit.overlay_type = PaneOverlayType.LINE
+		hit.distance_px = p_distance
+		hit.contains_pointer = p_contains
+		return hit
diff --git a/addons/tau-plot/plot/xy/line/line_hit_tester.gd.uid b/addons/tau-plot/plot/xy/line/line_hit_tester.gd.uid
new file mode 100644
index 0000000..d41c899
--- /dev/null
+++ b/addons/tau-plot/plot/xy/line/line_hit_tester.gd.uid
@@ -0,0 +1 @@
+uid://dh43for0yf2ab
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index f0a1ed8..1bf0708 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -6,13 +6,15 @@ const AxisId = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").AxisId
 const Axis = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").Axis
 const VisualAttributes = preload("res://addons/tau-plot/plot/xy/visual_attributes.gd").VisualAttributes
 const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_visual_attributes.gd").LineVisualAttributes
+const LineHitRecord := preload("res://addons/tau-plot/plot/xy/line/line_hit_record.gd").LineHitRecord
 
 
 # Draws line overlays from an XYLayout + Dataset.
 #
 # This renderer reads all samples through the Dataset public API (no direct
 # buffer/series access). Each contiguous run of valid samples is drawn with
-# one Godot draw call.
+# one Godot draw call when no hover emphasis applies, or up to three
+# draw calls when the hovered sample lies inside the run.
 #
 # Runtime behavior:
 # - NaN and Inf X or Y values are treated according to TauLineConfig.gap_policy.
@@ -38,14 +40,28 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 #   TauLineStyle.get_series_dash_px(global_series_index). Path selection is
 #   therefore per series: two series in the same overlay can run on
 #   different paths in the same frame.
-# - Path 1, fast path: resolved per-series dash length is 0. The run is
+# - Fast path: resolved per-series dash length is 0. The run is
 #   drawn with a single draw_polyline_colors() call.
-# - Path 2, dashed batched path: resolved per-series dash length is positive.
+# - Dashed batched path: resolved per-series dash length is positive.
 #   Dash phase is precomputed across the full run, the "on" intervals are
 #   collected into a flat segment array, and the run is drawn with a single
 #   draw_multiline_colors() call. The dash phase is continuous across all
 #   segments of the polyline.
 #
+# Hover behavior:
+# - When TauLineConfig.hoverable is true and set_hover_state() has flagged a
+#   sample as hovered, the per-sample color is routed through
+#   TauHoverConfig.hover_highlight_callback (or a built-in dim/brighten
+#   default) so non-hovered samples are de-emphasized.
+# - When the hovered sample lies inside a drawn run, the polyline is split
+#   into up to three contiguous parts at the hovered sample's adjacent real
+#   neighbors. The middle part is drawn at the per-series resolved hovered
+#   width from TauLineStyle.hovered_line_widths_px, clamped to be at least
+#   the per-series base width. The outer two parts keep the base width.
+#   Each part is one draw call. For dashed lines, each part inherits the
+#   cumulative arc-length offset from the polyline start, so the dash
+#   pattern stays continuous through the slices.
+#
 # Per-sample color and alpha resolution:
 # - Color resolution order: LineVisualAttributes.color_buffer, then
 #   LineVisualCallbacks.color_callback, then the per-series color from
@@ -53,6 +69,8 @@ const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_v
 # - Alpha resolution order: LineVisualAttributes.alpha_buffer, then
 #   LineVisualCallbacks.alpha_callback, then TauXYStyle.series_alpha.
 # - The resolved alpha overwrites the alpha channel of the resolved color.
+# - When the highlight feature is active, the resulting color is then
+#   routed through TauHoverConfig.hover_highlight_callback.
 # - Each vertex of the polyline carries its own resolved color. Colors are
 #   linearly interpolated by Godot between consecutive vertices.
 # - Synthetic step-mode intermediate vertices and SMOOTH_MONOTONE sub-samples
@@ -90,6 +108,20 @@ class LineRenderer extends Control:
 	# on every redraw.
 	var _smooth_non_monotonic_warned: bool = false
 
+	# Per-frame cache of every real sample drawn onto a polyline this frame.
+	# Rebuilt every _draw() so the cache never drifts from what is on screen.
+	var _hit_records: Array[LineHitRecord] = []
+
+	# Hover highlight state. When _highlight_active is true, the per-sample
+	# color is routed through the hover color callback (or a built-in
+	# dim/brighten default). When the hovered sample lies within a drawn
+	# run, the two segments adjacent to it are drawn at the per-series
+	# resolved hovered width clamped to be at least the per-series base width.
+	var _highlight_active: bool = false
+	var _hovered_series_id: int = -1
+	var _hovered_sample_index: int = -1
+	var _hover_highlight_callback: Callable = Callable()
+
 
 	func _init(p_layout: XYLayout,
 				p_dataset: Dataset,
@@ -136,6 +168,23 @@ class LineRenderer extends Control:
 		_xy_style = p_style
 
 
+	## Updates the hover highlight state. A change triggers a redraw so the
+	## line is repainted with the new emphasis slice and dimming pattern.
+	func set_hover_state(p_active: bool, p_series_id: int, p_sample_index: int, p_color_callback: Callable) -> void:
+		var changed := p_active != _highlight_active or p_series_id != _hovered_series_id or p_sample_index != _hovered_sample_index
+		_highlight_active = p_active
+		_hovered_series_id = p_series_id
+		_hovered_sample_index = p_sample_index
+		_hover_highlight_callback = p_color_callback
+		if changed:
+			queue_redraw()
+
+
+	## Returns the per-frame hit records cache. Treat as read-only.
+	func get_hit_records() -> Array[LineHitRecord]:
+		return _hit_records
+
+
 	## Creates a legend key Control for a line overlay.
 	func create_legend_key_control(_p_series_index: int) -> Control:
 		# TODO: implement create_legend_key_control for lines
@@ -147,6 +196,8 @@ class LineRenderer extends Control:
 	####################################################################################################
 
 	func _draw() -> void:
+		_hit_records.clear()
+
 		if _line_style == null:
 			push_error("LineRenderer: resolved TauLineStyle is null.")
 			return
@@ -189,12 +240,20 @@ class LineRenderer extends Control:
 		if width_px <= 0.0:
 			return
 		var dash_px: int = _line_style.get_series_dash_px(global_series_index)
+		var hover_width_px: float = max(_line_style.get_series_hovered_width_px(global_series_index), width_px)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
 
 		var run := PackedVector2Array()
 		var run_colors := PackedColorArray()
+		# Parallel arrays describing the real samples appended to the current
+		# run. real_polyline_indices[k] is the index into `run` where the k-th
+		# real sample of this run landed before any post-processing
+		# (SMOOTH_MONOTONE resampling). The dataset index is needed so the
+		# finalizer can locate the hovered sample within the current run.
+		var real_polyline_indices := PackedInt32Array()
+		var real_dataset_indices := PackedInt32Array()
 
 		var is_shared_x := _dataset.get_mode() == Dataset.Mode.SHARED_X
 		var sample_count := _dataset.get_series_sample_count(series_id)
@@ -203,25 +262,42 @@ class LineRenderer extends Control:
 			var x_value: float = float(_dataset.get_shared_x(i)) if is_shared_x else float(_dataset.get_series_x(series_id, i))
 			if is_nan(x_value) or is_inf(x_value) or not _is_x_value_valid_for_scale(x_value):
 				if not bridge:
-					_finalize_run(run, run_colors, width_px, interpolation, dash_px)
+					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
 					run = PackedVector2Array()
 					run_colors = PackedColorArray()
+					real_polyline_indices = PackedInt32Array()
+					real_dataset_indices = PackedInt32Array()
 				continue
 
 			var y_value := _dataset.get_series_y(series_id, i)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					_finalize_run(run, run_colors, width_px, interpolation, dash_px)
+					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
 					run = PackedVector2Array()
 					run_colors = PackedColorArray()
+					real_polyline_indices = PackedInt32Array()
+					real_dataset_indices = PackedInt32Array()
 				continue
 
 			var x_px := _layout.map_x_to_px(_pane_index, x_value)
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
+			var screen_pos := _layout.map_point_to_screen(x_px, y_px)
 			var sample_color := _resolve_sample_color(p_series_index, i, x_value, y_value)
-			_append_with_interpolation(run, run_colors, _layout.map_point_to_screen(x_px, y_px), sample_color, interpolation)
+			_append_with_interpolation(run, run_colors, screen_pos, sample_color, interpolation)
+			# The real sample is always the last vertex appended by
+			# _append_with_interpolation, regardless of the interpolation mode.
+			real_polyline_indices.append(run.size() - 1)
+			real_dataset_indices.append(i)
 
-		_finalize_run(run, run_colors, width_px, interpolation, dash_px)
+			var record := LineHitRecord.new()
+			record.series_id = series_id
+			record.sample_index = i
+			record.x_value = x_value
+			record.y_value = y_value
+			record.screen_position = screen_pos
+			_hit_records.append(record)
+
+		_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
 
 
 	func _draw_series_categorical(p_series_index: int) -> void:
@@ -231,6 +307,7 @@ class LineRenderer extends Control:
 		if width_px <= 0.0:
 			return
 		var dash_px: int = _line_style.get_series_dash_px(global_series_index)
+		var hover_width_px: float = max(_line_style.get_series_hovered_width_px(global_series_index), width_px)
 		var y_axis_id := _get_y_axis_id_for_series(series_id)
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
@@ -238,24 +315,39 @@ class LineRenderer extends Control:
 		var categories := _layout.domain.x_categories
 		var run := PackedVector2Array()
 		var run_colors := PackedColorArray()
+		var real_polyline_indices := PackedInt32Array()
+		var real_dataset_indices := PackedInt32Array()
 		var sample_count := _dataset.get_series_sample_count(series_id)
 
 		for cat_idx in range(sample_count):
 			var y_value := _dataset.get_series_y(series_id, cat_idx)
 			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
 				if not bridge:
-					_finalize_run(run, run_colors, width_px, interpolation, dash_px)
+					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
 					run = PackedVector2Array()
 					run_colors = PackedColorArray()
+					real_polyline_indices = PackedInt32Array()
+					real_dataset_indices = PackedInt32Array()
 				continue
 
 			var x_px := _layout.map_x_category_center_to_px(_pane_index, cat_idx)
 			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
+			var screen_pos := _layout.map_point_to_screen(x_px, y_px)
 			var x_value: Variant = categories[cat_idx]
 			var sample_color := _resolve_sample_color(p_series_index, cat_idx, x_value, y_value)
-			_append_with_interpolation(run, run_colors, _layout.map_point_to_screen(x_px, y_px), sample_color, interpolation)
+			_append_with_interpolation(run, run_colors, screen_pos, sample_color, interpolation)
+			real_polyline_indices.append(run.size() - 1)
+			real_dataset_indices.append(cat_idx)
+
+			var record := LineHitRecord.new()
+			record.series_id = series_id
+			record.sample_index = cat_idx
+			record.x_value = x_value
+			record.y_value = y_value
+			record.screen_position = screen_pos
+			_hit_records.append(record)
 
-		_finalize_run(run, run_colors, width_px, interpolation, dash_px)
+		_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
 
 
 	# Each appended sample (real or synthetic) gets the new sample's color.
@@ -294,36 +386,184 @@ class LineRenderer extends Control:
 	# For SMOOTH_MONOTONE the run is first replaced by its Fritsch-Carlson piecewise cubic resampling.
 	# Runs of fewer than two points are silently dropped.
 	#
-	# When p_dash_px is 0, the polyline is emitted via path 1 (draw_polyline_colors).
-	# Otherwise it is emitted via path 2: dash phase is precomputed across the
-	# whole polyline and the resulting "on" intervals are flushed in a single
-	# draw_multiline_colors() call. p_dash_px is the resolved per-series dash
-	# length obtained from TauLineStyle.get_series_dash_px().
-	func _finalize_run(p_run: PackedVector2Array, p_run_colors: PackedColorArray, p_width_px: float, p_mode: TauLineConfig.InterpolationMode, p_dash_px: int) -> void:
+	# Path selection per series (no hover):
+	#   - p_dash_px == 0: one draw_polyline_colors call.
+	#   - p_dash_px  > 0: one draw_multiline_colors call after dash precomputation.
+	#
+	# When the hovered sample belongs to this run, the polyline is split into
+	# up to three contiguous parts and each part is drawn with its own draw
+	# call:
+	#   - Part A: vertices [0 .. slice_start], drawn at p_width_px.
+	#   - Part B: vertices [slice_start .. slice_end], drawn at p_hover_width_px.
+	#   - Part C: vertices [slice_end .. last], drawn at p_width_px.
+	# slice_start is the polyline index of the hovered sample's previous real
+	# neighbor, or the hovered sample itself when it has no previous neighbor
+	# in this run. slice_end is the index of the next real neighbor, or the
+	# hovered sample itself when it has none. For dashed lines, the dash phase
+	# is carried across parts using each part's cumulative arc-length offset
+	# from the polyline start, so the dash pattern stays continuous through
+	# the slices.
+	#
+	# p_real_polyline_indices and p_real_dataset_indices are parallel arrays
+	# whose length equals the number of real samples appended to this run.
+	# real_polyline_indices[k] is the index in p_run where the k-th real
+	# sample landed. real_dataset_indices[k] is the dataset sample index for
+	# that real sample.
+	func _finalize_run(p_run: PackedVector2Array, p_run_colors: PackedColorArray, p_real_polyline_indices: PackedInt32Array, p_real_dataset_indices: PackedInt32Array, p_series_id: int, p_width_px: float, p_hover_width_px: float, p_mode: TauLineConfig.InterpolationMode, p_dash_px: int) -> void:
 		var polyline: PackedVector2Array = p_run
 		var polyline_colors: PackedColorArray = p_run_colors
+		var real_polyline_indices: PackedInt32Array = p_real_polyline_indices
 		if p_mode == TauLineConfig.InterpolationMode.SMOOTH_MONOTONE and p_run.size() > 2:
 			var resampled := _resample_smooth_monotone(p_run, p_run_colors)
 			polyline = resampled[0]
 			polyline_colors = resampled[1]
+			# In SMOOTH_MONOTONE the input run holds only real samples, so
+			# every entry in p_real_polyline_indices is its own input index
+			# and the resample's input-to-output map is the new mapping.
+			real_polyline_indices = resampled[2]
 		if polyline.size() < 2:
 			return
 
 		var dash_px: int = max(p_dash_px, 0)
-		if dash_px <= 0:
-			draw_polyline_colors(polyline, polyline_colors, p_width_px)
+		var slice_bounds := _resolve_hover_slice_bounds(real_polyline_indices, p_real_dataset_indices, p_series_id)
+
+		if slice_bounds.is_empty():
+			# No hover emphasis: draw the entire polyline in a single call.
+			_draw_polyline_segment(polyline, polyline_colors, 0, polyline.size() - 1, p_width_px, dash_px, 0.0)
+			return
+
+		var slice_start: int = slice_bounds[0]
+		var slice_end: int = slice_bounds[1]
+		var last: int = polyline.size() - 1
+
+		# Precompute cumulative arc length so each part inherits a starting
+		# phase that keeps the dash pattern continuous across the slices.
+		# When dash_px is 0 the offsets are still computed but ignored by the
+		# solid path.
+		var arc_at_slice_start: float = _arc_length_to_index(polyline, slice_start)
+		var arc_at_slice_end: float = arc_at_slice_start + _arc_length_between(polyline, slice_start, slice_end)
+
+		# Part A: from the polyline start up to and including slice_start.
+		_draw_polyline_segment(polyline, polyline_colors, 0, slice_start, p_width_px, dash_px, 0.0)
+		# Part B: the two adjacent portions, emphasized.
+		_draw_polyline_segment(polyline, polyline_colors, slice_start, slice_end, p_hover_width_px, dash_px, arc_at_slice_start)
+		# Part C: from slice_end to the polyline end.
+		_draw_polyline_segment(polyline, polyline_colors, slice_end, last, p_width_px, dash_px, arc_at_slice_end)
+
+
+	# Resolves the polyline-vertex bounds of the hover-emphasized slice for
+	# the current run, or an empty array when no emphasis applies.
+	#
+	# Returns [slice_start, slice_end] when the hovered sample belongs to the
+	# current run and has at least one real neighbor that produces a non-zero
+	# slice. slice_start is the polyline index of the previous real neighbor
+	# (or the hovered sample itself when it has no previous neighbor).
+	# slice_end is the polyline index of the next real neighbor (or the
+	# hovered sample itself when it has none).
+	#
+	# When the hovered sample has been deduplicated by SMOOTH_MONOTONE
+	# resampling (consecutive real samples sharing the same screen X), it
+	# shares its polyline index with the surviving neighbor it was deduped
+	# against, so the slice still covers the right neighborhood.
+	func _resolve_hover_slice_bounds(p_real_polyline_indices: PackedInt32Array, p_real_dataset_indices: PackedInt32Array, p_series_id: int) -> PackedInt32Array:
+		if not _highlight_active or _hovered_series_id != p_series_id or _hovered_sample_index < 0:
+			return PackedInt32Array()
+		var real_count: int = p_real_dataset_indices.size()
+		if real_count <= 1:
+			return PackedInt32Array()
+
+		var hover_pos_in_run: int = -1
+		for k in range(real_count):
+			if p_real_dataset_indices[k] == _hovered_sample_index:
+				hover_pos_in_run = k
+				break
+		if hover_pos_in_run < 0:
+			return PackedInt32Array()
+
+		var hovered_idx: int = p_real_polyline_indices[hover_pos_in_run]
+		var slice_start: int = hovered_idx
+		if hover_pos_in_run > 0:
+			slice_start = p_real_polyline_indices[hover_pos_in_run - 1]
+		var slice_end: int = hovered_idx
+		if hover_pos_in_run < real_count - 1:
+			slice_end = p_real_polyline_indices[hover_pos_in_run + 1]
+
+		if slice_end <= slice_start:
+			return PackedInt32Array()
+
+		var bounds := PackedInt32Array()
+		bounds.append(slice_start)
+		bounds.append(slice_end)
+		return bounds
+
+
+	# Draws a contiguous polyline part bounded by the given vertex indices,
+	# inclusive on both ends. Dispatches to draw_polyline_colors or _draw_dashed_polyline
+	# based on p_dash_px. p_phase_offset seeds the dash phase tracker so
+	# callers can chain multiple parts with continuous phase across slice
+	# boundaries.
+	#
+	# Parts of length less than 2 are skipped: a single-vertex slice cannot
+	# produce any drawable segment.
+	func _draw_polyline_segment(p_polyline: PackedVector2Array, p_polyline_colors: PackedColorArray, p_first: int, p_last: int, p_width_px: float, p_dash_px: int, p_phase_offset: float) -> void:
+		if p_last <= p_first:
+			return
+		# A non-fragmented full run is the common case: avoid the slice copy.
+		if p_first == 0 and p_last == p_polyline.size() - 1:
+			if p_dash_px <= 0:
+				draw_polyline_colors(p_polyline, p_polyline_colors, p_width_px)
+			else:
+				_draw_dashed_polyline(p_polyline, p_polyline_colors, p_width_px, float(p_dash_px), p_phase_offset)
+			return
+
+		var sub_polyline := PackedVector2Array()
+		var sub_colors := PackedColorArray()
+		var sub_size: int = p_last - p_first + 1
+		sub_polyline.resize(sub_size)
+		sub_colors.resize(sub_size)
+		for j in range(sub_size):
+			sub_polyline[j] = p_polyline[p_first + j]
+			sub_colors[j] = p_polyline_colors[p_first + j]
+
+		if p_dash_px <= 0:
+			draw_polyline_colors(sub_polyline, sub_colors, p_width_px)
 		else:
-			_draw_dashed_polyline(polyline, polyline_colors, p_width_px, float(dash_px))
+			_draw_dashed_polyline(sub_polyline, sub_colors, p_width_px, float(p_dash_px), p_phase_offset)
+
+
+	func _arc_length_to_index(p_polyline: PackedVector2Array, p_index: int) -> float:
+		if p_index <= 0:
+			return 0.0
+		var total: float = 0.0
+		for i in range(p_index):
+			total += p_polyline[i].distance_to(p_polyline[i + 1])
+		return total
+
+
+	func _arc_length_between(p_polyline: PackedVector2Array, p_first: int, p_last: int) -> float:
+		if p_last <= p_first:
+			return 0.0
+		var total: float = 0.0
+		for i in range(p_first, p_last):
+			total += p_polyline[i].distance_to(p_polyline[i + 1])
+		return total
 
 
 	# Builds the flat segment array of "on" dash intervals along p_polyline and
-	# emits it with a single draw_multiline_colors() call. The dash period is
+	# draws it with a single draw_multiline_colors() call. The dash period is
 	# 2 * p_dash_px (one "on" length followed by one "off" length of equal
 	# size). Dash phase is tracked as a single scalar that advances along the
 	# polyline arc length, so the pattern is continuous across consecutive
 	# segments and does not reset at sample positions.
 	#
-	# draw_multiline_colors takes one solid color per emitted segment (a pair
+	# p_phase_offset seeds the phase tracker at the start of the polyline,
+	# expressed in pixels of arc length. It lets a caller draw a contiguous
+	# polyline as multiple back-to-back parts (each with its own draw call)
+	# and keep the dash pattern continuous across the part boundaries: each
+	# subsequent part passes the cumulative arc length from the original
+	# polyline start as its phase offset.
+	#
+	# draw_multiline_colors takes one solid color per drawn segment (a pair
 	# of points). Each "on" interval gets the color of its midpoint along the
 	# enclosing polyline segment, computed by linear interpolation between the
 	# two flanking polyline-vertex colors. For typical dash sizes this is a
@@ -332,10 +572,10 @@ class LineRenderer extends Control:
 	#
 	# Degenerate segments (zero length) are skipped: they cannot carry any
 	# dash and do not advance the phase.
-	func _draw_dashed_polyline(p_polyline: PackedVector2Array, p_polyline_colors: PackedColorArray, p_width_px: float, p_dash_px: float) -> void:
+	func _draw_dashed_polyline(p_polyline: PackedVector2Array, p_polyline_colors: PackedColorArray, p_width_px: float, p_dash_px: float, p_phase_offset: float = 0.0) -> void:
 		var period: float = p_dash_px * 2.0
 		var n := p_polyline.size()
-		var phase: float = 0.0
+		var phase: float = fposmod(p_phase_offset, period)
 		var segments := PackedVector2Array()
 		var segment_colors := PackedColorArray()
 
@@ -399,53 +639,71 @@ class LineRenderer extends Control:
 	# screen X are dropped since the secant slope is undefined at h = 0. The
 	# matching color entries are dropped at the same indices.
 	# Inputs that are not monotonic in either direction fall back to the raw
-	# polyline for that run and emit a one-shot warning.
+	# polyline for that run and push a one-shot warning.
 	#
 	# Sub-sample colors are linearly interpolated between the two flanking
 	# kept-sample colors so that the visual color gradient matches what
 	# draw_polyline_colors would produce on a LINEAR polyline through the
 	# same kept samples.
 	#
-	# Returns [points: PackedVector2Array, colors: PackedColorArray].
+	# Returns [points: PackedVector2Array, colors: PackedColorArray, input_to_output: PackedInt32Array].
+	# input_to_output[i] is the index in the returned points array where input point i lands.
+	# Dropped inputs (consecutive same-screen-X duplicates) inherit the output index of the
+	# neighbor they were deduplicated against.
 	func _resample_smooth_monotone(p_points: PackedVector2Array, p_colors: PackedColorArray) -> Array:
+		var input_count := p_points.size()
 		var direction := _detect_monotonic_x_direction(p_points)
 		if direction == 0:
 			if not _smooth_non_monotonic_warned:
 				push_warning("LineRenderer: SMOOTH_MONOTONE received samples whose screen X is not monotonic. Falling back to a straight polyline for the affected run. Use LINEAR interpolation if your data does not have a monotonic X parameter.")
 				_smooth_non_monotonic_warned = true
-			return [p_points, p_colors]
+			var identity := PackedInt32Array()
+			identity.resize(input_count)
+			for i in range(input_count):
+				identity[i] = i
+			return [p_points, p_colors, identity]
 
 		var ascending: bool = direction > 0
 
 		# Build strictly increasing X arrays, dropping flat-X duplicates.
-		# Colors are kept in lock-step with the kept points.
+		# Colors are kept in lock-step with the kept points. kept_of[i] is the
+		# kept-array index for original input i, used later to remap real
+		# samples to their output-polyline position. Dropped inputs share
+		# their surviving neighbor's kept index.
 		var xs := PackedFloat32Array()
 		var ys := PackedFloat32Array()
 		var cs := PackedColorArray()
-		var input_count := p_points.size()
+		var kept_of := PackedInt32Array()
+		kept_of.resize(input_count)
 		if ascending:
 			xs.append(p_points[0].x)
 			ys.append(p_points[0].y)
 			cs.append(p_colors[0])
+			kept_of[0] = 0
 			for i in range(1, input_count):
 				if p_points[i].x > xs[xs.size() - 1]:
 					xs.append(p_points[i].x)
 					ys.append(p_points[i].y)
 					cs.append(p_colors[i])
+				kept_of[i] = xs.size() - 1
 		else:
 			xs.append(p_points[input_count - 1].x)
 			ys.append(p_points[input_count - 1].y)
 			cs.append(p_colors[input_count - 1])
+			kept_of[input_count - 1] = 0
 			for i in range(input_count - 2, -1, -1):
 				if p_points[i].x > xs[xs.size() - 1]:
 					xs.append(p_points[i].x)
 					ys.append(p_points[i].y)
 					cs.append(p_colors[i])
+				kept_of[i] = xs.size() - 1
 
 		var n := xs.size()
 		if n < 2:
 			# All inputs collapsed to a single screen X. Nothing to draw.
-			return [PackedVector2Array(), PackedColorArray()]
+			var empty_map := PackedInt32Array()
+			empty_map.resize(input_count)
+			return [PackedVector2Array(), PackedColorArray(), empty_map]
 		if n == 2:
 			# Two distinct X values produce a straight line through Hermite
 			# with both tangents equal to the secant slope. Short-circuit.
@@ -458,7 +716,15 @@ class LineRenderer extends Control:
 			if not ascending:
 				trivial.reverse()
 				trivial_colors.reverse()
-			return [trivial, trivial_colors]
+			var trivial_map := PackedInt32Array()
+			trivial_map.resize(input_count)
+			for i in range(input_count):
+				var kept_idx: int = kept_of[i]
+				if ascending:
+					trivial_map[i] = kept_idx
+				else:
+					trivial_map[i] = 1 - kept_idx
+			return [trivial, trivial_colors, trivial_map]
 
 		var tangents := _fritsch_carlson_tangents(xs, ys)
 
@@ -504,7 +770,20 @@ class LineRenderer extends Control:
 		if not ascending:
 			out.reverse()
 			out_colors.reverse()
-		return [out, out_colors]
+
+		# Build the input-to-output index map. In the ascending output, kept
+		# input k sits at out[k * SUBS]. When the output is reversed for a
+		# descending input, that position becomes (out_size - 1 - k * SUBS).
+		var input_to_output := PackedInt32Array()
+		input_to_output.resize(input_count)
+		for i in range(input_count):
+			var kept_idx: int = kept_of[i]
+			var out_idx: int = kept_idx * _SMOOTH_SUBDIVISIONS
+			if not ascending:
+				out_idx = out_size - 1 - out_idx
+			input_to_output[i] = out_idx
+
+		return [out, out_colors, input_to_output]
 
 
 	# Returns +1 if screen X is strictly monotonically increasing across the
@@ -630,14 +909,28 @@ class LineRenderer extends Control:
 	# Per-sample color and alpha resolution
 	####################################################################################################
 
-	# Combined per-sample color resolution. The alpha resolved by
-	# _resolve_sample_alpha overwrites the alpha channel of the color resolved
-	# by _resolve_sample_color_only.
+	# Combined per-sample color resolution. Alpha overwrites the resolved
+	# color's alpha channel, then the result is routed through the
+	# hover-highlight callback when active.
 	func _resolve_sample_color(p_series_index: int, p_sample_index: int, p_x_value: Variant, p_y_value: float) -> Color:
 		var base := _resolve_sample_color_only(p_series_index, p_sample_index, p_x_value, p_y_value)
 		var alpha := _resolve_sample_alpha(p_series_index, p_sample_index, p_x_value, p_y_value)
 		base.a = clampf(alpha, 0.0, 1.0)
-		return base
+		return _apply_hover_color(base, _get_line_series_id(p_series_index), p_sample_index)
+
+
+	# Applies the hover-highlight callback (or the built-in dim/brighten
+	# default) to a resolved per-sample color. Returns the color unchanged
+	# when the highlight feature is off.
+	func _apply_hover_color(p_color: Color, p_series_id: int, p_sample_index: int) -> Color:
+		if not _highlight_active:
+			return p_color
+		var is_hovered: bool = (p_series_id == _hovered_series_id) and (p_sample_index == _hovered_sample_index)
+		if _hover_highlight_callback.is_valid():
+			return _hover_highlight_callback.call(p_color, is_hovered)
+		if is_hovered:
+			return p_color.lightened(0.15)
+		return Color(p_color, 0.5)
 
 
 	func _resolve_sample_color_only(p_series_index: int, p_sample_index: int, p_x_value: Variant, p_y_value: float) -> Color:
diff --git a/addons/tau-plot/plot/xy/line/line_style.gd b/addons/tau-plot/plot/xy/line/line_style.gd
index 2666f6a..4b2b486 100644
--- a/addons/tau-plot/plot/xy/line/line_style.gd
+++ b/addons/tau-plot/plot/xy/line/line_style.gd
@@ -26,6 +26,20 @@ class_name TauLineStyle extends Resource
 const DEFAULT_LINE_WIDTHS_PX: Array[float] = [2.0]
 @export var line_widths_px: Array[float] = [2.0]
 
+## Per-series cycle of line widths in pixels for the two segments adjacent to
+## the hovered sample. Each entry sets the hovered width for one series, with
+## the array indexed cyclically by series index using modulo: series
+## [code]i[/code] reads entry [code]i % hovered_line_widths_px.size()[/code].
+## An empty array means no hover emphasis: the segments adjacent to the
+## hovered sample are drawn at the resolved [member line_widths_px] value for
+## that series.
+##
+## At draw time, the resolved per-series hovered width is clamped to be at
+## least the resolved per-series base width from [member line_widths_px], so
+## a thicker series never becomes thinner on hover.
+const DEFAULT_HOVERED_LINE_WIDTHS_PX: Array[float] = [3.0]
+@export var hovered_line_widths_px: Array[float] = [3.0]
+
 ## Per-series dash length cycle, in pixels. Each entry sets the dash length
 ## for one series, with the array indexed cyclically by series index using
 ## modulo: series [code]i[/code] reads entry
@@ -53,6 +67,19 @@ func get_series_width_px(p_series_index: int) -> float:
 	return max(entry, 0.0)
 
 
+## Returns the resolved hovered line width in pixels for the given series
+## index. An empty [member hovered_line_widths_px] returns [code]0.0[/code]
+## as a "no hover emphasis" sentinel. The renderer clamps the result against
+## the per-series base width from [member line_widths_px], so the empty-array
+## case naturally falls back to the base width and never produces a thinner
+## line on hover.
+func get_series_hovered_width_px(p_series_index: int) -> float:
+	if hovered_line_widths_px.is_empty():
+		return 0.0
+	var entry: float = hovered_line_widths_px[p_series_index % hovered_line_widths_px.size()]
+	return max(entry, 0.0)
+
+
 ## Returns the resolved dash length in pixels for the given series index.
 func get_series_dash_px(p_series_index: int) -> int:
 	if dash_lengths_px.is_empty():
@@ -72,9 +99,10 @@ func get_series_dash_px(p_series_index: int) -> int:
 ##   1. [code]<key>_N[/code] sets the value for series N across all panes.
 ##   2. [code]<key>_N_P[/code] overrides series N in pane P only.
 ##
-## For [code]line_widths_px[/code] the keys are [code]line_width_px_N[/code]
-## and [code]line_width_px_N_P[/code]. For [code]dash_lengths_px[/code] they
-## are [code]line_dash_px_N[/code] and [code]line_dash_px_N_P[/code].
+## Theme key prefixes:
+##   - [member line_widths_px]:         [code]line_width_px[/code]
+##   - [member hovered_line_widths_px]: [code]line_hovered_width_px[/code]
+##   - [member dash_lengths_px]:        [code]line_dash_px[/code]
 ##
 ## This method writes every property unconditionally because it is called on
 ## the resolved instance, not on the user-provided resource.
@@ -110,6 +138,31 @@ func load_from_theme(p_control: Control, p_pane_index: int) -> void:
 		line_widths_px[pane_width_index] = max(float(p_control.get_theme_constant(key)), 0.0)
 		pane_width_index += 1
 
+	# hovered_line_widths_px: two-level indexed lookup.
+	# Level 1 (global): line_hovered_width_px_N
+	var global_hovered: Array[float] = []
+	var hovered_index := 0
+	while true:
+		var key := "line_hovered_width_px_%d" % hovered_index
+		if not p_control.has_theme_constant(key):
+			break
+		global_hovered.append(max(float(p_control.get_theme_constant(key)), 0.0))
+		hovered_index += 1
+
+	if not global_hovered.is_empty():
+		hovered_line_widths_px = global_hovered
+
+	# Level 2 (per-pane): line_hovered_width_px_N_P overrides series N in pane P.
+	var pane_hovered_index := 0
+	while true:
+		var key := "line_hovered_width_px_%d_%d" % [pane_hovered_index, p_pane_index]
+		if not p_control.has_theme_constant(key):
+			break
+		if pane_hovered_index >= hovered_line_widths_px.size():
+			hovered_line_widths_px.resize(pane_hovered_index + 1)
+		hovered_line_widths_px[pane_hovered_index] = max(float(p_control.get_theme_constant(key)), 0.0)
+		pane_hovered_index += 1
+
 	# dash_lengths_px: two-level indexed lookup.
 	# Level 1 (global): line_dash_px_N
 	var global_dashes: Array[int] = []
@@ -153,6 +206,10 @@ func apply_overrides_from(p_user_style: TauLineStyle) -> void:
 	if _is_line_widths_overridden(p_user_style.line_widths_px):
 		line_widths_px = p_user_style.line_widths_px.duplicate()
 
+	# hovered_line_widths_px: element-wise comparison against the default array.
+	if _is_hovered_line_widths_overridden(p_user_style.hovered_line_widths_px):
+		hovered_line_widths_px = p_user_style.hovered_line_widths_px.duplicate()
+
 	# dash_lengths_px: element-wise comparison against the default array.
 	if _is_dash_lengths_overridden(p_user_style.dash_lengths_px):
 		dash_lengths_px = p_user_style.dash_lengths_px.duplicate()
@@ -195,6 +252,11 @@ func is_equal_to(p_other: TauLineStyle) -> bool:
 	for i in range(line_widths_px.size()):
 		if line_widths_px[i] != p_other.line_widths_px[i]:
 			return false
+	if hovered_line_widths_px.size() != p_other.hovered_line_widths_px.size():
+		return false
+	for i in range(hovered_line_widths_px.size()):
+		if hovered_line_widths_px[i] != p_other.hovered_line_widths_px[i]:
+			return false
 	if dash_lengths_px.size() != p_other.dash_lengths_px.size():
 		return false
 	for i in range(dash_lengths_px.size()):
@@ -224,6 +286,17 @@ static func _is_line_widths_overridden(p_widths: Array[float]) -> bool:
 	return false
 
 
+## Returns true if [param p_widths] differs from DEFAULT_HOVERED_LINE_WIDTHS_PX
+## using a size + element loop (safest approach for typed arrays in GDScript).
+static func _is_hovered_line_widths_overridden(p_widths: Array[float]) -> bool:
+	if p_widths.size() != DEFAULT_HOVERED_LINE_WIDTHS_PX.size():
+		return true
+	for i in range(p_widths.size()):
+		if p_widths[i] != DEFAULT_HOVERED_LINE_WIDTHS_PX[i]:
+			return true
+	return false
+
+
 ## Returns true if [param p_dashes] differs from DEFAULT_DASH_LENGTHS_PX using
 ## a size + element loop (safest approach for typed arrays in GDScript).
 static func _is_dash_lengths_overridden(p_dashes: Array[int]) -> bool:
diff --git a/addons/tau-plot/plot/xy/xy_plot.gd b/addons/tau-plot/plot/xy/xy_plot.gd
index 096d4d2..e617b9e 100644
--- a/addons/tau-plot/plot/xy/xy_plot.gd
+++ b/addons/tau-plot/plot/xy/xy_plot.gd
@@ -43,6 +43,7 @@ const ScatterHitTester = preload("res://addons/tau-plot/plot/xy/scatter/scatter_
 
 const LineRenderer := preload("res://addons/tau-plot/plot/xy/line/line_renderer.gd").LineRenderer
 const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_visual_attributes.gd").LineVisualAttributes
+const LineHitTester = preload("res://addons/tau-plot/plot/xy/line/line_hit_tester.gd").LineHitTester
 
 
 # External references (provided via setup)
@@ -410,6 +411,13 @@ func setup(
 				_scatter_renderers[pane_index],
 				_dataset, _xy_layout))
 
+		if _line_renderers[pane_index] != null:
+			testers.append(LineHitTester.new(
+				pane_index,
+				_line_config_per_pane[pane_index],
+				_line_renderers[pane_index],
+				_dataset, _xy_layout))
+
 		hit_testers_per_pane.append(testers)
 
 	_hover_controller = HoverController.new()

From 56ca21885c80b954502963e6e6aec0abecac32e4 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Fri, 1 May 2026 12:26:03 +0200
Subject: [PATCH 12/23] cleanup

---
 addons/tau-plot/plot/xy/bar/bar_hit_tester.gd         |  2 +-
 addons/tau-plot/plot/xy/bar/bar_renderer.gd           | 10 +++++-----
 addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd |  2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd b/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd
index e7d136a..d4be55b 100644
--- a/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd
@@ -35,7 +35,7 @@ class BarHitTester extends OverlayHitTester:
 		return _bar_config.hoverable
 
 
-	func get_preferred_hover_mode() -> int:
+	func get_preferred_hover_mode() -> HoverMode:
 		return HoverMode.X_ALIGNED
 
 
diff --git a/addons/tau-plot/plot/xy/bar/bar_renderer.gd b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
index 6be3632..c0c88ea 100644
--- a/addons/tau-plot/plot/xy/bar/bar_renderer.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
@@ -145,6 +145,11 @@ class BarRenderer extends Control:
 			queue_redraw()
 
 
+	## Returns the per-frame hit records cache. Treat as read-only.
+	func get_hit_records() -> Array[BarHitRecord]:
+		return _hit_records
+
+
 	## Creates a legend key Control for a bar overlay: a filled square with alpha.
 	## Reads fill color and alpha from resolved styles on this renderer instance.
 	## Does not set custom_minimum_size, so the legend applies its default key_size_px.
@@ -536,11 +541,6 @@ class BarRenderer extends Control:
 		_hit_records.append(record)
 
 
-	## Returns the per-frame hit records cache. Treat as read-only.
-	func get_hit_records() -> Array[BarHitRecord]:
-		return _hit_records
-
-
 	func _draw_grouped_bars(p_pane_rect: Rect2, p_series_count: int) -> void:
 		if p_series_count <= 0:
 			return
diff --git a/addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd b/addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd
index ef2d573..1eda034 100644
--- a/addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd
+++ b/addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd
@@ -43,7 +43,7 @@ class ScatterHitTester extends OverlayHitTester:
 
 
 	## Scatter points are best selected individually, so NEAREST is preferred.
-	func get_preferred_hover_mode() -> int:
+	func get_preferred_hover_mode() -> HoverMode:
 		return HoverMode.NEAREST
 
 

From 223f8ddf11e8de3cfecca29a98e38fcad13a2cfb Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Sat, 2 May 2026 17:53:19 +0200
Subject: [PATCH 13/23] Fix stacking order (breaking change)

---
 addons/tau-plot/plot/xy/xy_plot.gd            |  22 ++
 .../stacking_order/test_bar_stacking_order.gd | 349 ++++++++++++++++++
 .../test_bar_stacking_order.gd.uid            |   1 +
 .../test_bar_stacking_order.tscn              |  85 +++++
 4 files changed, 457 insertions(+)
 create mode 100644 addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd
 create mode 100644 addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd.uid
 create mode 100644 addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.tscn

diff --git a/addons/tau-plot/plot/xy/xy_plot.gd b/addons/tau-plot/plot/xy/xy_plot.gd
index e617b9e..9438de2 100644
--- a/addons/tau-plot/plot/xy/xy_plot.gd
+++ b/addons/tau-plot/plot/xy/xy_plot.gd
@@ -231,6 +231,13 @@ func setup(
 				# Unknown overlay types are rejected by validation.
 				pass
 
+	# Bindings populate the per-pane series id arrays in binding-iteration
+	# order, which is unrelated to dataset order. Sorting here makes the
+	# stacking order predictable (layer 0 = first declared series).
+	for pane_index in range(pane_count):
+		_sort_series_ids_by_dataset_index(_bar_series_ids_per_pane[pane_index])
+		_sort_series_ids_by_dataset_index(_line_series_ids_per_pane[pane_index])
+
 	# Domain + layout creation
 	_xy_domain_overrides = XYDomainOverrides.new()
 	_xy_domain_overrides.init_panes(pane_count)
@@ -941,6 +948,21 @@ func _attach_legend_outside(p_legend: Control, p_position: Position) -> void:
 			hbox.move_child(p_legend, hbox.get_child_count() - 1)
 
 
+func _sort_series_ids_by_dataset_index(p_ids: PackedInt64Array) -> void:
+	# Insertion sort. PackedInt64Array exposes no sort_custom, and the per-pane
+	# series count is small enough that anything more elaborate is overkill.
+	var count := p_ids.size()
+	for sorted_count in range(count):
+		# Pick the next unsorted element and find where it belongs in the already-sorted [0, sorted_count) part.
+		var current_sid := p_ids[sorted_count]
+		var current_dataset_index := _dataset.get_series_index_by_id(current_sid)
+		var insert_at := sorted_count
+		while insert_at > 0 and _dataset.get_series_index_by_id(p_ids[insert_at - 1]) > current_dataset_index:
+			p_ids[insert_at] = p_ids[insert_at - 1]
+			insert_at -= 1
+		p_ids[insert_at] = current_sid
+
+
 func _init_pane_dirty_flags(p_pane_count: int) -> void:
 	_xy_dirty_panes.resize(p_pane_count)
 	_bars_dirty_panes.resize(p_pane_count)
diff --git a/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd b/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd
new file mode 100644
index 0000000..19828ca
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd
@@ -0,0 +1,349 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot1.title = "[CONTINUOUS] with stacked_normalization = NONE"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.NONE
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_c, sb_a, sb_b]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot2.title = "[CONTINUOUS] with stacked_normalization = FRACTION"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.FRACTION
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_b, sb_a, sb_c]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot3.title = "[CONTINUOUS] with stacked_normalization = PERCENT"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.format_tick_label = func(label: String) -> String:
+		return label + "%"
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.PERCENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_c, sb_b]
+
+	%TestPlot3.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four"])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot4.title = "[CATEGORICAL] with stacked_normalization = NONE"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.NONE
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_b, sb_a, sb_c]
+
+	%TestPlot4.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four"])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot5.title = "[CATEGORICAL] with stacked_normalization = FRACTION"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.FRACTION
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_c, sb_a, sb_b]
+
+	%TestPlot5.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four"])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot6.title = "[CATEGORICAL] with stacked_normalization = PERCENT"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.format_tick_label = func(label: String) -> String:
+		return label + "%"
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.PERCENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_b, sb_c, sb_a]
+
+	%TestPlot6.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd.uid b/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd.uid
new file mode 100644
index 0000000..66bf9da
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd.uid
@@ -0,0 +1 @@
+uid://dc8xbkxehai5e
diff --git a/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.tscn b/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.tscn
new file mode 100644
index 0000000..f6539b7
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.tscn
@@ -0,0 +1,85 @@
+[gd_scene load_steps=3 format=3 uid="uid://dtphakr4ucelg"]
+
+[ext_resource type="Script" uid="uid://dc8xbkxehai5e" path="res://addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd" id="1_6dmnp"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_p3gyn"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_6dmnp")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test stacking order which is dataset order, not binding order."
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_p3gyn")
+title = "[CONTINUOUS] with stacked_normalization = NONE"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_p3gyn")
+title = "[CONTINUOUS] with stacked_normalization = FRACTION"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_p3gyn")
+title = "[CONTINUOUS] with stacked_normalization = PERCENT"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_p3gyn")
+title = "[CATEGORICAL] with stacked_normalization = NONE"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_p3gyn")
+title = "[CATEGORICAL] with stacked_normalization = FRACTION"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_p3gyn")
+title = "[CATEGORICAL] with stacked_normalization = PERCENT"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"

From 7c5807b221d9202d7532b28c7053b59460f38b7e Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Sun, 3 May 2026 10:22:33 +0200
Subject: [PATCH 14/23] Callbacks receive the y raw value (breaking change)

---
 addons/tau-plot/plot/xy/bar/bar_renderer.gd | 35 ++++++++++++---------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/addons/tau-plot/plot/xy/bar/bar_renderer.gd b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
index c0c88ea..5dabab5 100644
--- a/addons/tau-plot/plot/xy/bar/bar_renderer.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
@@ -469,14 +469,15 @@ class BarRenderer extends Control:
 
 	## Draws a single bar, orientation-aware, using a StyleBox.
 	## Records a BarHitRecord for every bar that survives clipping.
+	## [param p_y_value] is stored in the hit record.
+	## [param p_y_value_for_callbacks] is passed to color, alpha, and style_box callbacks.
 	func _draw_bar(p_pane_rect: Rect2, p_x_screen: float, p_y_from_screen: float,
 				   p_y_to_screen: float, p_thickness_px: float, p_color: Color,
 				   p_series_index: int, p_sample_index: int,
-				   p_x_value: Variant, p_y_value: float) -> void:
+				   p_x_value: Variant, p_y_value: float,
+				   p_y_value_for_callbacks: float) -> void:
 		var x_is_horizontal: bool = _layout._x_is_horizontal
 
-		# TODO: replace the x_is_horizontal branches below with XYLayout.map_point_to_screen() once it exists.
-
 		# Build the clipped screen rect.
 		var rect: Rect2
 		if x_is_horizontal:
@@ -512,7 +513,7 @@ class BarRenderer extends Control:
 				return
 			rect = Rect2(Vector2(clipped_left, clipped_top), Vector2(w, h))
 
-		var style_box := _get_style_box(p_series_index, p_sample_index, p_x_value, p_y_value)
+		var style_box := _get_style_box(p_series_index, p_sample_index, p_x_value, p_y_value_for_callbacks)
 		var final_color := _apply_hover_color(p_color, _get_bar_series_id(p_series_index), p_sample_index)
 		_set_style_box_color(style_box, final_color)
 
@@ -592,7 +593,7 @@ class BarRenderer extends Control:
 				var base_color := _get_bar_color(series_index, category_index, x_value, y_value)
 				var alpha_override := _get_bar_alpha(series_index, category_index, x_value, y_value)
 				var color := _apply_alpha_override(base_color, alpha_override)
-				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, category_index, x_value, y_value)
+				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, category_index, x_value, y_value, y_value)
 
 
 	func _draw_grouped_bars_continuous(p_pane_rect: Rect2, p_series_count: int) -> void:
@@ -651,7 +652,7 @@ class BarRenderer extends Control:
 				var base_color := _get_bar_color(series_index, i, x_value, y_value)
 				var alpha_override := _get_bar_alpha(series_index, i, x_value, y_value)
 				var color := _apply_alpha_override(base_color, alpha_override)
-				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, i, x_value, y_value)
+				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, i, x_value, y_value, y_value)
 
 
 	func _draw_stacked_bars(p_pane_rect: Rect2, p_series_count: int) -> void:
@@ -744,11 +745,13 @@ class BarRenderer extends Control:
 
 				var x_value: Variant = categories[category_index]
 				var y_value: float = segment["y1"]
-				var base_color := _get_bar_color(series_index, category_index, x_value, y_value)
-				var alpha_override := _get_bar_alpha(series_index, category_index, x_value, y_value)
+				# Callbacks see the raw dataset value, not the stacked top.
+				var y_raw: float = _dataset.get_series_y(_get_bar_series_id(series_index), category_index)
+				var base_color := _get_bar_color(series_index, category_index, x_value, y_raw)
+				var alpha_override := _get_bar_alpha(series_index, category_index, x_value, y_raw)
 				var color := _apply_alpha_override(base_color, alpha_override)
 
-				_draw_bar(p_pane_rect, group_center_px, y0_px, y1_px, bar_width_px, color, series_index, category_index, x_value, y_value)
+				_draw_bar(p_pane_rect, group_center_px, y0_px, y1_px, bar_width_px, color, series_index, category_index, x_value, y_value, y_raw)
 
 
 	func _draw_stacked_bars_continuous_shared_x(p_pane_rect: Rect2, p_series_count: int) -> void:
@@ -846,11 +849,13 @@ class BarRenderer extends Control:
 				var y1_px := _layout.map_y_to_px(_pane_index, segment["y1"], stacked_axis_id)
 
 				var y_value: float = segment["y1"]
-				var base_color := _get_bar_color(series_index, i, x_value, y_value)
-				var alpha_override := _get_bar_alpha(series_index, i, x_value, y_value)
+				# Callbacks see the raw dataset value, not the stacked top.
+				var y_raw: float = _dataset.get_series_y(_get_bar_series_id(series_index), i)
+				var base_color := _get_bar_color(series_index, i, x_value, y_raw)
+				var alpha_override := _get_bar_alpha(series_index, i, x_value, y_raw)
 				var color := _apply_alpha_override(base_color, alpha_override)
 
-				_draw_bar(p_pane_rect, group_center_px, y0_px, y1_px, bar_width_px, color, series_index, i, x_value, y_value)
+				_draw_bar(p_pane_rect, group_center_px, y0_px, y1_px, bar_width_px, color, series_index, i, x_value, y_value, y_raw)
 
 
 	func _draw_independent_bars(p_pane_rect: Rect2, p_series_count: int) -> void:
@@ -903,7 +908,7 @@ class BarRenderer extends Control:
 				var alpha_override := _get_bar_alpha(series_index, category_index, x_value, y_value)
 				var color := _apply_alpha_override(base_color, alpha_override)
 
-				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, category_index, x_value, y_value)
+				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, category_index, x_value, y_value, y_value)
 
 
 	func _draw_independent_bars_continuous(p_pane_rect: Rect2, p_series_count: int) -> void:
@@ -960,7 +965,7 @@ class BarRenderer extends Control:
 				var alpha_override := _get_bar_alpha(series_index, i, x_value, y_value)
 				var color := _apply_alpha_override(base_color, alpha_override)
 
-				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, i, x_value, y_value)
+				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, i, x_value, y_value, y_value)
 
 
 	func _draw_independent_bars_continuous_per_series_x(p_pane_rect: Rect2, p_series_count: int) -> void:
@@ -1004,7 +1009,7 @@ class BarRenderer extends Control:
 				var alpha_override := _get_bar_alpha(series_index, i, x_value, y_value)
 				var color := _apply_alpha_override(base_color, alpha_override)
 
-				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, i, x_value, y_value)
+				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, i, x_value, y_value, y_value)
 
 
 	func _get_series_draw_order(p_series_count: int) -> Array[int]:

From 2e6dec8773e86e482049289d555b60c4b7d95b3c Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Sun, 3 May 2026 12:38:03 +0200
Subject: [PATCH 15/23] Hit carry both plotted and raw values (breaking change)

---
 addons/tau-plot/plot/xy/bar/bar_hit_record.gd | 11 ++--
 addons/tau-plot/plot/xy/bar/bar_hit_tester.gd |  3 +-
 addons/tau-plot/plot/xy/bar/bar_renderer.gd   | 54 ++++++++++---------
 .../tau-plot/plot/xy/hover/hover_formatter.gd |  2 +-
 addons/tau-plot/plot/xy/hover/sample_hit.gd   | 10 +++-
 .../tau-plot/plot/xy/line/line_hit_record.gd  | 10 +++-
 .../tau-plot/plot/xy/line/line_hit_tester.gd  |  3 +-
 addons/tau-plot/plot/xy/line/line_renderer.gd |  6 ++-
 .../plot/xy/scatter/scatter_hit_tester.gd     |  9 ++--
 9 files changed, 69 insertions(+), 39 deletions(-)

diff --git a/addons/tau-plot/plot/xy/bar/bar_hit_record.gd b/addons/tau-plot/plot/xy/bar/bar_hit_record.gd
index 5f09859..e53c485 100644
--- a/addons/tau-plot/plot/xy/bar/bar_hit_record.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_hit_record.gd
@@ -9,9 +9,14 @@ class BarHitRecord extends RefCounted:
 	## Float for continuous x, String for categorical.
 	var x_value: Variant
 
-	## Plotted y value. For STACKED with normalization, this is the scaled
-	## value matching the y-axis labels, not the raw dataset value.
-	var y_value: float
+	## Y position the bar's top is drawn at, in axis units.
+	## Differs from y_raw_value when STACKED is on (cumulative top) or when
+	## FRACTION/PERCENT normalization is on.
+	var y_plotted_value: float
+
+	## Original dataset value, before any stacking, normalization, or
+	## accumulation. Equal to y_plotted_value when STACKED is off.
+	var y_raw_value: float
 
 	## Painted rectangle, clipped to the pane.
 	var rect: Rect2
diff --git a/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd b/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd
index d4be55b..59eed8f 100644
--- a/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_hit_tester.gd
@@ -106,7 +106,8 @@ class BarHitTester extends OverlayHitTester:
 		hit.series_name = _dataset.get_series_name(p_record.series_id)
 		hit.sample_index = p_record.sample_index
 		hit.x_value = p_record.x_value
-		hit.y_value = p_record.y_value
+		hit.y_plotted_value = p_record.y_plotted_value
+		hit.y_raw_value = p_record.y_raw_value
 		hit.screen_position = p_record.anchor
 		hit.pane_index = _pane_index
 		hit.overlay_type = PaneOverlayType.BAR
diff --git a/addons/tau-plot/plot/xy/bar/bar_renderer.gd b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
index 5dabab5..b2b6928 100644
--- a/addons/tau-plot/plot/xy/bar/bar_renderer.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
@@ -469,27 +469,37 @@ class BarRenderer extends Control:
 
 	## Draws a single bar, orientation-aware, using a StyleBox.
 	## Records a BarHitRecord for every bar that survives clipping.
-	## [param p_y_value] is stored in the hit record.
-	## [param p_y_value_for_callbacks] is passed to color, alpha, and style_box callbacks.
-	func _draw_bar(p_pane_rect: Rect2, p_x_screen: float, p_y_from_screen: float,
-				   p_y_to_screen: float, p_thickness_px: float, p_color: Color,
-				   p_series_index: int, p_sample_index: int,
-				   p_x_value: Variant, p_y_value: float,
-				   p_y_value_for_callbacks: float) -> void:
+	## p_pane_rect: pane bounds used to clip the bar rect.
+	## p_x_axis_px: bar center along the x-axis direction, in pixels.
+	## p_y_axis_from_px: baseline end of the bar along the y-axis direction, in pixels.
+	## p_y_axis_to_px: tip end of the bar along the y-axis direction, in pixels.
+	## p_thickness_px: bar thickness across the x-axis direction, in pixels.
+	## p_color: fill color before hover remap.
+	## p_series_index: index into the bar series list, not the dataset series id.
+	## p_sample_index: sample index / category index.
+	## p_x_value: float for continuous x, String for categorical.
+	## p_y_plotted_value: cumulative top in STACKED mode, scaled when FRACTION/PERCENT is on.
+	## p_y_raw_value: original dataset value. Equal to p_y_plotted_value when STACKED is off.
+	func _draw_bar(
+			p_pane_rect: Rect2, p_x_axis_px: float, p_y_axis_from_px: float, p_y_axis_to_px: float,
+			p_thickness_px: float, p_color: Color,
+			p_series_index: int, p_sample_index: int,
+			p_x_value: Variant, p_y_plotted_value: float, p_y_raw_value: float
+		) -> void:
 		var x_is_horizontal: bool = _layout._x_is_horizontal
 
 		# Build the clipped screen rect.
 		var rect: Rect2
 		if x_is_horizontal:
-			var left := p_x_screen - p_thickness_px * 0.5
+			var left := p_x_axis_px - p_thickness_px * 0.5
 			var right := left + p_thickness_px
 			var clipped_left := max(left, p_pane_rect.position.x)
 			var clipped_right := min(right, p_pane_rect.position.x + p_pane_rect.size.x)
 			var w: float = clipped_right - clipped_left
 			if w <= 0.0:
 				return
-			var top := min(p_y_from_screen, p_y_to_screen)
-			var bottom := max(p_y_from_screen, p_y_to_screen)
+			var top := min(p_y_axis_from_px, p_y_axis_to_px)
+			var bottom := max(p_y_axis_from_px, p_y_axis_to_px)
 			var clipped_top := max(top, p_pane_rect.position.y)
 			var clipped_bottom := min(bottom, p_pane_rect.position.y + p_pane_rect.size.y)
 			var h: float = clipped_bottom - clipped_top
@@ -497,15 +507,15 @@ class BarRenderer extends Control:
 				return
 			rect = Rect2(Vector2(clipped_left, clipped_top), Vector2(w, h))
 		else:
-			var top := p_x_screen - p_thickness_px * 0.5
+			var top := p_x_axis_px - p_thickness_px * 0.5
 			var bottom := top + p_thickness_px
 			var clipped_top := max(top, p_pane_rect.position.y)
 			var clipped_bottom := min(bottom, p_pane_rect.position.y + p_pane_rect.size.y)
 			var h: float = clipped_bottom - clipped_top
 			if h <= 0.0:
 				return
-			var left := min(p_y_from_screen, p_y_to_screen)
-			var right := max(p_y_from_screen, p_y_to_screen)
+			var left := min(p_y_axis_from_px, p_y_axis_to_px)
+			var right := max(p_y_axis_from_px, p_y_axis_to_px)
 			var clipped_left := max(left, p_pane_rect.position.x)
 			var clipped_right := min(right, p_pane_rect.position.x + p_pane_rect.size.x)
 			var w: float = clipped_right - clipped_left
@@ -513,30 +523,26 @@ class BarRenderer extends Control:
 				return
 			rect = Rect2(Vector2(clipped_left, clipped_top), Vector2(w, h))
 
-		var style_box := _get_style_box(p_series_index, p_sample_index, p_x_value, p_y_value_for_callbacks)
+		var style_box := _get_style_box(p_series_index, p_sample_index, p_x_value, p_y_raw_value)
 		var final_color := _apply_hover_color(p_color, _get_bar_series_id(p_series_index), p_sample_index)
 		_set_style_box_color(style_box, final_color)
 
 		if style_box is StyleBoxFlat:
-			var tip_at_min: bool = (p_y_to_screen < p_y_from_screen)
+			var tip_at_min: bool = (p_y_axis_to_px < p_y_axis_from_px)
 			_remap_corners_and_borders(style_box as StyleBoxFlat, _derived_source_ref as StyleBoxFlat, x_is_horizontal, tip_at_min)
 
 		draw_style_box(style_box, rect)
 
-		# Tip-center in screen coords, un-clipped so the anchor stays on the data point
-		# even when the bar is partly outside the pane.
-		# TODO: use XYLayout.map_point_to_screen() once it exists.
-		var anchor: Vector2
-		if x_is_horizontal:
-			anchor = Vector2(p_x_screen, p_y_to_screen)
-		else:
-			anchor = Vector2(p_y_to_screen, p_x_screen)
+		# Tip center in screen coords, un-clipped so the anchor stays on the data
+		# point even when the bar is partly outside the pane.
+		var anchor := _layout.map_point_to_screen(p_x_axis_px, p_y_axis_to_px)
 
 		var record := BarHitRecord.new()
 		record.series_id = _get_bar_series_id(p_series_index)
 		record.sample_index = p_sample_index
 		record.x_value = p_x_value
-		record.y_value = p_y_value
+		record.y_plotted_value = p_y_plotted_value
+		record.y_raw_value = p_y_raw_value
 		record.rect = rect
 		record.anchor = anchor
 		_hit_records.append(record)
diff --git a/addons/tau-plot/plot/xy/hover/hover_formatter.gd b/addons/tau-plot/plot/xy/hover/hover_formatter.gd
index 3953868..1e8d86e 100644
--- a/addons/tau-plot/plot/xy/hover/hover_formatter.gd
+++ b/addons/tau-plot/plot/xy/hover/hover_formatter.gd
@@ -98,7 +98,7 @@ class HoverFormatter extends RefCounted:
 	## Formats the y value of a hit, using axis format_tick_label if available.
 	func _format_hit_y_value(p_hit: SampleHit) -> String:
 		var span := _get_y_domain_span(p_hit)
-		var raw_str := _format_value(p_hit.y_value, span, _precision_digits)
+		var raw_str := _format_value(p_hit.y_raw_value, span, _precision_digits)
 		return _apply_y_format_callback(raw_str, p_hit)
 
 
diff --git a/addons/tau-plot/plot/xy/hover/sample_hit.gd b/addons/tau-plot/plot/xy/hover/sample_hit.gd
index 2722a9e..e104fcc 100644
--- a/addons/tau-plot/plot/xy/hover/sample_hit.gd
+++ b/addons/tau-plot/plot/xy/hover/sample_hit.gd
@@ -16,8 +16,14 @@ class SampleHit extends RefCounted:
 	## X value: float for continuous axes, String for categorical.
 	var x_value: Variant
 
-	## Y value.
-	var y_value: float
+	## Y position the sample is drawn at, in axis units.
+	## Differs from y_raw_value when STACKED is on (cumulative top) or when
+	## FRACTION/PERCENT normalization is on.
+	var y_plotted_value: float
+
+	## Original dataset value, before any stacking, normalization, or
+	## accumulation. Equal to y_plotted_value when STACKED is off.
+	var y_raw_value: float
 
 	## Screen position of the data point in plot-local coordinates.
 	## For bars this is the top-center of the bar (or the relevant edge
diff --git a/addons/tau-plot/plot/xy/line/line_hit_record.gd b/addons/tau-plot/plot/xy/line/line_hit_record.gd
index 52f610b..a0d38d1 100644
--- a/addons/tau-plot/plot/xy/line/line_hit_record.gd
+++ b/addons/tau-plot/plot/xy/line/line_hit_record.gd
@@ -11,8 +11,14 @@ class LineHitRecord extends RefCounted:
 	## Float for continuous x, String for categorical.
 	var x_value: Variant
 
-	## Plotted y value.
-	var y_value: float
+	## Y position the polyline vertex is drawn at, in axis units.
+	## Differs from y_raw_value when STACKED is on (cumulative top) or when
+	## FRACTION/PERCENT normalization is on.
+	var y_plotted_value: float
+
+	## Original dataset value, before any stacking, normalization, or
+	## accumulation. Equal to y_plotted_value when STACKED is off.
+	var y_raw_value: float
 
 	## Real sample position in pane-local screen coordinates.
 	var screen_position: Vector2
diff --git a/addons/tau-plot/plot/xy/line/line_hit_tester.gd b/addons/tau-plot/plot/xy/line/line_hit_tester.gd
index df8be79..d5c7679 100644
--- a/addons/tau-plot/plot/xy/line/line_hit_tester.gd
+++ b/addons/tau-plot/plot/xy/line/line_hit_tester.gd
@@ -156,7 +156,8 @@ class LineHitTester extends OverlayHitTester:
 		hit.series_name = _dataset.get_series_name(p_record.series_id)
 		hit.sample_index = p_record.sample_index
 		hit.x_value = p_record.x_value
-		hit.y_value = p_record.y_value
+		hit.y_plotted_value = p_record.y_plotted_value
+		hit.y_raw_value = p_record.y_raw_value
 		hit.screen_position = p_record.screen_position
 		hit.pane_index = _pane_index
 		hit.overlay_type = PaneOverlayType.LINE
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index 1bf0708..c595cf1 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -293,7 +293,8 @@ class LineRenderer extends Control:
 			record.series_id = series_id
 			record.sample_index = i
 			record.x_value = x_value
-			record.y_value = y_value
+			record.y_plotted_value = y_value
+			record.y_raw_value = y_value
 			record.screen_position = screen_pos
 			_hit_records.append(record)
 
@@ -343,7 +344,8 @@ class LineRenderer extends Control:
 			record.series_id = series_id
 			record.sample_index = cat_idx
 			record.x_value = x_value
-			record.y_value = y_value
+			record.y_plotted_value = y_value
+			record.y_raw_value = y_value
 			record.screen_position = screen_pos
 			_hit_records.append(record)
 
diff --git a/addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd b/addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd
index 1eda034..a2f43a8 100644
--- a/addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd
+++ b/addons/tau-plot/plot/xy/scatter/scatter_hit_tester.gd
@@ -104,7 +104,8 @@ class ScatterHitTester extends OverlayHitTester:
 			hit.series_name = _dataset.get_series_name(hit.series_id)
 			hit.sample_index = sample_idx
 			hit.x_value = p_x_value
-			hit.y_value = _scatter_renderer.get_hover_y_value(i)
+			hit.y_plotted_value = _scatter_renderer.get_hover_y_value(i)
+			hit.y_raw_value = hit.y_plotted_value
 			hit.screen_position = screen_pos
 			hit.pane_index = _pane_index
 			hit.overlay_type = PaneOverlayType.SCATTER
@@ -153,7 +154,8 @@ class ScatterHitTester extends OverlayHitTester:
 			hit.series_name = _dataset.get_series_name(hit.series_id)
 			hit.sample_index = _scatter_renderer.get_hover_sample_index(i)
 			hit.x_value = _scatter_renderer.get_hover_x_value(i)
-			hit.y_value = _scatter_renderer.get_hover_y_value(i)
+			hit.y_plotted_value = _scatter_renderer.get_hover_y_value(i)
+			hit.y_raw_value = hit.y_plotted_value
 			hit.screen_position = screen_pos
 			hit.pane_index = _pane_index
 			hit.overlay_type = PaneOverlayType.SCATTER
@@ -213,7 +215,8 @@ class ScatterHitTester extends OverlayHitTester:
 		hit.series_name = _dataset.get_series_name(hit.series_id)
 		hit.sample_index = _scatter_renderer.get_hover_sample_index(p_cache_index)
 		hit.x_value = _scatter_renderer.get_hover_x_value(p_cache_index)
-		hit.y_value = _scatter_renderer.get_hover_y_value(p_cache_index)
+		hit.y_plotted_value = _scatter_renderer.get_hover_y_value(p_cache_index)
+		hit.y_raw_value = hit.y_plotted_value
 		hit.screen_position = _scatter_renderer.get_hover_screen_position(p_cache_index)
 		hit.pane_index = _pane_index
 		hit.overlay_type = PaneOverlayType.SCATTER

From 3b59c744ae84253abb67052fba822253b856aab1 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Sun, 3 May 2026 12:59:49 +0200
Subject: [PATCH 16/23] Tooltip no longer use axis-tick formatters (breaking
 change)

---
 .../tau-plot/plot/xy/hover/hover_formatter.gd | 46 +++----------------
 addons/tau-plot/plot/xy/xy_plot.gd            |  2 +-
 2 files changed, 7 insertions(+), 41 deletions(-)

diff --git a/addons/tau-plot/plot/xy/hover/hover_formatter.gd b/addons/tau-plot/plot/xy/hover/hover_formatter.gd
index 1e8d86e..eaa329b 100644
--- a/addons/tau-plot/plot/xy/hover/hover_formatter.gd
+++ b/addons/tau-plot/plot/xy/hover/hover_formatter.gd
@@ -6,22 +6,18 @@ const SeriesAxisAssignment := preload("res://addons/tau-plot/plot/xy/series_axis
 ## Produces human-readable strings from raw numeric values for tooltip display.
 ##
 ## Adapts decimal places to the visible domain span and a configurable
-## precision digit count. Honors user-provided format_tick_label callbacks
-## on axis configs when they are set.
+## precision digit count.
 class HoverFormatter extends RefCounted:
 	var _domain: XYDomain
-	var _domain_config: TauXYConfig
 	var _series_assignment: SeriesAxisAssignment
 	var _precision_digits: int
 
 
 	func _init(
 			p_domain: XYDomain,
-			p_domain_config: TauXYConfig,
 			p_series_assignment: SeriesAxisAssignment,
 			p_precision_digits: int) -> void:
 		_domain = p_domain
-		_domain_config = p_domain_config
 		_series_assignment = p_series_assignment
 		_precision_digits = p_precision_digits
 
@@ -85,21 +81,14 @@ class HoverFormatter extends RefCounted:
 		return "\n".join(lines)
 
 
-	## Formats the x value of a hit, using axis format_tick_label if available.
 	func _format_hit_x_value(p_hit: SampleHit) -> String:
 		if p_hit.x_value is String:
-			return _apply_x_format_callback(p_hit.x_value as String)
+			return p_hit.x_value as String
+		return _format_continuous_x_value(p_hit.x_value as float)
 
-		# Continuous x: format with domain-aware precision for tooltip display.
-		var raw_str := _format_continuous_x_value(p_hit.x_value as float)
-		return _apply_x_format_callback(raw_str)
 
-
-	## Formats the y value of a hit, using axis format_tick_label if available.
 	func _format_hit_y_value(p_hit: SampleHit) -> String:
-		var span := _get_y_domain_span(p_hit)
-		var raw_str := _format_value(p_hit.y_raw_value, span, _precision_digits)
-		return _apply_y_format_callback(raw_str, p_hit)
+		return _format_value(p_hit.y_raw_value, _get_y_domain_span(p_hit), _precision_digits)
 
 
 	## Formats a continuous x value for tooltip display.
@@ -110,8 +99,7 @@ class HoverFormatter extends RefCounted:
 	## places is derived from the x domain span and the configured precision
 	## digits.
 	func _format_continuous_x_value(p_value: float) -> String:
-		var span := _get_x_domain_span()
-		return _format_value(p_value, span, _precision_digits)
+		return _format_value(p_value, _get_x_domain_span(), _precision_digits)
 
 
 	## Formats a float with precision derived from the domain span.
@@ -120,12 +108,8 @@ class HoverFormatter extends RefCounted:
 	## represents roughly 1/(10^p_precision_digits) of the span. When values
 	## are extremely small or extremely large, scientific notation is used.
 	static func _format_value(p_value: float, p_domain_span: float, p_precision_digits: int) -> String:
-		# The span must be strictly positive (which is guaranteed by XYDomain).
-		if p_domain_span <= 0.0:
-			push_error("HoverFormatter: domain span must be > 0, got %f" % p_domain_span)
-			return String.num(p_value, 3)
-
 		# Compute decimals so precision is ~span / 10^p_precision_digits.
+		# The domain span is strictly positive (guaranteed by XYDomain).
 		var decimals := maxi(0, -int(floor(log(p_domain_span) / log(10.0))) + p_precision_digits)
 
 		# If we would need more than 12 decimal places, switch to scientific
@@ -153,21 +137,3 @@ class HoverFormatter extends RefCounted:
 		var pane_domain := _domain.get_pane_domain(pane_idx)
 		var y_domain := pane_domain.get_y_axis_domain(y_axis_id)
 		return y_domain.max_val - y_domain.min_val
-
-
-	## Applies the x axis format_tick_label callback if set.
-	func _apply_x_format_callback(p_text: String) -> String:
-		var x_cfg := _domain_config.x_axis
-		if x_cfg == null or not x_cfg.format_tick_label.is_valid():
-			return p_text
-		return x_cfg.format_tick_label.call(p_text)
-
-
-	## Applies the y axis format_tick_label callback if set for the hit's pane and axis.
-	func _apply_y_format_callback(p_text: String, p_hit: SampleHit) -> String:
-		var y_axis_id: int = _series_assignment.get_y_axis_id_for_series(p_hit.series_id, p_hit.pane_index)
-		var pane_config: TauPaneConfig = _domain_config.panes[p_hit.pane_index]
-		var y_cfg := pane_config.get_y_axis_config(y_axis_id)
-		if y_cfg == null or not y_cfg.format_tick_label.is_valid():
-			return p_text
-		return y_cfg.format_tick_label.call(p_text)
diff --git a/addons/tau-plot/plot/xy/xy_plot.gd b/addons/tau-plot/plot/xy/xy_plot.gd
index 9438de2..3df5348 100644
--- a/addons/tau-plot/plot/xy/xy_plot.gd
+++ b/addons/tau-plot/plot/xy/xy_plot.gd
@@ -396,7 +396,7 @@ func setup(
 
 	# Hover setup
 	var tooltip_precision_digits := p_hover_config.tooltip_precision_digits if p_hover_config != null else 3
-	var formatter := HoverFormatter.new(_xy_domain, _domain_config, _series_assignment, tooltip_precision_digits)
+	var formatter := HoverFormatter.new(_xy_domain, _series_assignment, tooltip_precision_digits)
 
 	# Create per-pane hit testers.
 	var hit_testers_per_pane: Array = []

From 39191bdbbbb0dc48c1a9241f50c3f8a279a35c84 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Sun, 3 May 2026 14:51:16 +0200
Subject: [PATCH 17/23] Add StackedNegativePolicy (breaking change)

---
 addons/tau-plot/plot/xy/bar/bar_config.gd     |  25 ++-
 addons/tau-plot/plot/xy/bar/bar_renderer.gd   | 151 +++++++++---------
 addons/tau-plot/plot/xy/bar/bar_validator.gd  |  23 +--
 addons/tau-plot/plot/xy/line/line_config.gd   |  20 ++-
 .../plot/xy/stacked_negative_policy.gd        |  12 ++
 .../plot/xy/stacked_negative_policy.gd.uid    |   1 +
 .../tau-plot/plot/xy/stacked_pinned_range.gd  |  31 ++++
 .../plot/xy/stacked_pinned_range.gd.uid       |   1 +
 addons/tau-plot/plot/xy/xy_plot.gd            |  13 +-
 9 files changed, 179 insertions(+), 98 deletions(-)
 create mode 100644 addons/tau-plot/plot/xy/stacked_negative_policy.gd
 create mode 100644 addons/tau-plot/plot/xy/stacked_negative_policy.gd.uid
 create mode 100644 addons/tau-plot/plot/xy/stacked_pinned_range.gd
 create mode 100644 addons/tau-plot/plot/xy/stacked_pinned_range.gd.uid

diff --git a/addons/tau-plot/plot/xy/bar/bar_config.gd b/addons/tau-plot/plot/xy/bar/bar_config.gd
index bf867e6..1795851 100644
--- a/addons/tau-plot/plot/xy/bar/bar_config.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_config.gd
@@ -24,6 +24,17 @@ enum BarMode
 const StackedNormalization = preload("res://addons/tau-plot/plot/xy/stacked_normalization.gd").StackedNormalization
 @export var stacked_normalization: StackedNormalization = StackedNormalization.NONE
 
+const StackedNegativePolicy = preload("res://addons/tau-plot/plot/xy/stacked_negative_policy.gd").StackedNegativePolicy
+
+## How negative values are handled in STACKED mode:
+## - SKIP_NEGATIVES (default) drops negative samples entirely from the stack.
+## - DIVERGING splits each X into an upper stack of positive values and
+## a lower stack of negative values, both anchored at zero.
+## - SIGNED_SUM is not a valid choice for bars: bar geometry cannot represent a
+## downward dip without overlapping rectangles. Setting it produces a validation
+## error.
+@export var stacked_negative_policy: StackedNegativePolicy = StackedNegativePolicy.SKIP_NEGATIVES
+
 
 enum BarWidthPolicy
 {
@@ -150,6 +161,8 @@ func is_equal_to(p_other: TauPaneOverlayConfig) -> bool:
 		return false
 	if stacked_normalization != other.stacked_normalization:
 		return false
+	if stacked_negative_policy != other.stacked_negative_policy:
+		return false
 
 	if bar_width_policy != other.bar_width_policy:
 		return false
@@ -180,10 +193,11 @@ func is_equal_to(p_other: TauPaneOverlayConfig) -> bool:
 # Returns true if the change between this and p_other affects layout/domain.
 # Returns false if the change only affects visual appearance.
 #
-# Only mode and stacked_normalization affect the domain (stacking changes Y
-# bounds via _apply_bar_domain_overrides_y). All width, gap, and spacing
-# properties are visual-only: they control how bars are drawn within a fixed
-# domain but do not feed into domain or tick computation.
+# mode, stacked_normalization, and stacked_negative_policy affect the domain:
+# stacking changes Y bounds, normalization pins the range, and the negative
+# policy decides whether the lower half-axis exists. All width, gap, and
+# spacing properties are visual-only: they control how bars are drawn within
+# a fixed domain but do not feed into domain or tick computation.
 func has_layout_affecting_change(p_other: TauPaneOverlayConfig) -> bool:
 	var other := p_other as TauBarConfig
 	if other == null:
@@ -198,4 +212,7 @@ func has_layout_affecting_change(p_other: TauPaneOverlayConfig) -> bool:
 	if mode == BarMode.STACKED and stacked_normalization != other.stacked_normalization:
 		return true
 
+	if mode == BarMode.STACKED and stacked_negative_policy != other.stacked_negative_policy:
+		return true
+
 	return false
diff --git a/addons/tau-plot/plot/xy/bar/bar_renderer.gd b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
index b2b6928..ac0cd50 100644
--- a/addons/tau-plot/plot/xy/bar/bar_renderer.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
@@ -16,7 +16,8 @@ const BarHitRecord := preload("res://addons/tau-plot/plot/xy/bar/bar_hit_record.
 # - NaN and Inf are always silently skipped
 # - Logarithmic Y scales: y <= 0 are skipped
 # - Logarithmic X scales: x <= 0 are skipped
-# - STACKED mode: negative values are skipped (would produce misleading visualization)
+# - STACKED mode: negative values follow TauBarConfig.stacked_negative_policy
+#   (DIVERGING by default: a separate downward stack from zero).
 # BarValidator is expected to enforce:
 # - dataset shape constraints for the chosen mode,
 # - length consistency in SHARED_X mode,
@@ -661,6 +662,76 @@ class BarRenderer extends Control:
 				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, i, x_value, y_value, y_value)
 
 
+	# Builds one X column's worth of stacked bar segments in dataset order,
+	# applying the active normalization and negative policy. The returned list
+	# drives the second-pass painter, which looks up segments by series_index.
+	func _compute_stacked_segments_at(p_series_count: int, p_sample_index: int) -> Array:
+		var normalization := _bar_config.stacked_normalization
+		var policy := _bar_config.stacked_negative_policy
+
+		# DIVERGING needs positive and absolute-negative totals tracked
+		# separately so each half-stack normalizes against its own total.
+		var pos_total := 0.0
+		var neg_total_abs := 0.0
+		if normalization != TauBarConfig.StackedNormalization.NONE:
+			for series_index in range(p_series_count):
+				var series_id := _get_bar_series_id(series_index)
+				var y_value := _dataset.get_series_y(series_id, p_sample_index)
+				if is_nan(y_value) or is_inf(y_value):
+					continue
+				if y_value >= 0.0:
+					pos_total += y_value
+				else:
+					neg_total_abs += -y_value
+
+		var pos_scale := 1.0
+		var neg_scale := 1.0
+		match normalization:
+			TauBarConfig.StackedNormalization.FRACTION:
+				pos_scale = 1.0 / pos_total if pos_total > 0.0 else 0.0
+				neg_scale = 1.0 / neg_total_abs if neg_total_abs > 0.0 else 0.0
+
+			TauBarConfig.StackedNormalization.PERCENT:
+				pos_scale = 100.0 / pos_total if pos_total > 0.0 else 0.0
+				neg_scale = 100.0 / neg_total_abs if neg_total_abs > 0.0 else 0.0
+
+		var segments: Array = []
+		var accum_pos := 0.0
+		var accum_neg := 0.0
+
+		for series_index in range(p_series_count):
+			var series_id := _get_bar_series_id(series_index)
+			var y_raw := _dataset.get_series_y(series_id, p_sample_index)
+			if is_nan(y_raw) or is_inf(y_raw):
+				continue
+
+			match policy:
+				TauBarConfig.StackedNegativePolicy.SKIP_NEGATIVES:
+					if y_raw < 0.0:
+						continue
+					var y := y_raw * pos_scale
+					var y0 := accum_pos
+					var y1 := accum_pos + y
+					segments.append({"series_index": series_index, "y0": y0, "y1": y1})
+					accum_pos = y1
+
+				TauBarConfig.StackedNegativePolicy.DIVERGING:
+					if y_raw >= 0.0:
+						var y := y_raw * pos_scale
+						var y0 := accum_pos
+						var y1 := accum_pos + y
+						segments.append({"series_index": series_index, "y0": y0, "y1": y1})
+						accum_pos = y1
+					else:
+						var y := y_raw * neg_scale
+						var y0 := accum_neg
+						var y1 := accum_neg + y
+						segments.append({"series_index": series_index, "y0": y0, "y1": y1})
+						accum_neg = y1
+
+		return segments
+
+
 	func _draw_stacked_bars(p_pane_rect: Rect2, p_series_count: int) -> void:
 		# Validator ensures: STACKED requires SHARED_X and SHARED y-axis
 		if p_series_count <= 0:
@@ -677,6 +748,7 @@ class BarRenderer extends Control:
 				push_error("Unexpected x-axis type %d" % int(x_config.type))
 
 
+	# FIXME: the second pass here duplicates _draw_stacked_bars_continuous_shared_x almost line-for-line.
 	func _draw_stacked_bars_categorical(p_pane_rect: Rect2, p_series_count: int) -> void:
 		var stacked_axis_id := _get_y_axis_id_for_series(_get_bar_series_id(0))
 		var categories := _layout.domain.x_categories
@@ -690,44 +762,8 @@ class BarRenderer extends Control:
 		# First pass: compute all segments for all categories (in dataset order for stacking)
 		var all_segments: Array = []  # Array of arrays, one per category. FIXME Godot 4.5 does not support nested typed collections.
 		all_segments.resize(n)
-
 		for category_index in range(n):
-			var total := 0.0
-			if _bar_config.stacked_normalization != TauBarConfig.StackedNormalization.NONE:
-				for series_index in range(p_series_count):
-					var series_id := _get_bar_series_id(series_index)
-					var y_value := _dataset.get_series_y(series_id, category_index)
-					if is_nan(y_value) or is_inf(y_value):
-						continue
-					if y_value < 0.0:
-						continue  # STACKED: skip negative values for total calculation
-					total += y_value
-
-			var scale := 1.0
-			if _bar_config.stacked_normalization == TauBarConfig.StackedNormalization.FRACTION:
-				scale = 1.0 / total if total > 0.0 else 0.0
-			elif _bar_config.stacked_normalization == TauBarConfig.StackedNormalization.PERCENT:
-				scale = 100.0 / total if total > 0.0 else 0.0
-
-			# Compute segments for this category in dataset order
-			var segments: Array = []
-			var accum := 0.0
-			for series_index in range(p_series_count):
-				var series_id := _get_bar_series_id(series_index)
-				var y_raw := _dataset.get_series_y(series_id, category_index)
-				if is_nan(y_raw) or is_inf(y_raw):
-					continue
-				if y_raw < 0.0:
-					continue  # STACKED: skip negative values
-
-				var y := y_raw * scale
-				var y0 := accum
-				var y1 := accum + y
-
-				segments.append({"series_index": series_index, "y0": y0, "y1": y1})
-				accum = y1
-
-			all_segments[category_index] = segments
+			all_segments[category_index] = _compute_stacked_segments_at(p_series_count, category_index)
 
 		# Second pass: paint in z_order (series first, then categories)
 		var draw_order := _get_series_draw_order(p_series_count)
@@ -760,6 +796,7 @@ class BarRenderer extends Control:
 				_draw_bar(p_pane_rect, group_center_px, y0_px, y1_px, bar_width_px, color, series_index, category_index, x_value, y_value, y_raw)
 
 
+	# FIXME: the second pass here duplicates _draw_stacked_bars_categorical almost line-for-line.
 	func _draw_stacked_bars_continuous_shared_x(p_pane_rect: Rect2, p_series_count: int) -> void:
 		var stacked_axis_id := _get_y_axis_id_for_series(_get_bar_series_id(0))
 		var n := _dataset.get_shared_sample_count()
@@ -771,7 +808,6 @@ class BarRenderer extends Control:
 		# First pass: compute all segments for all X positions (in dataset order for stacking)
 		var all_segments: Array = []  # Array of arrays, one per X position. FIXME Godot 4.5 does not support nested typed collections.
 		all_segments.resize(n)
-
 		for i in range(n):
 			var x_value := float(_dataset.get_shared_x(i))
 			if is_nan(x_value) or is_inf(x_value):
@@ -781,42 +817,7 @@ class BarRenderer extends Control:
 				all_segments[i] = []
 				continue
 
-			var total := 0.0
-			if _bar_config.stacked_normalization != TauBarConfig.StackedNormalization.NONE:
-				for series_index in range(p_series_count):
-					var series_id := _get_bar_series_id(series_index)
-					var y_value := _dataset.get_series_y(series_id, i)
-					if is_nan(y_value) or is_inf(y_value):
-						continue
-					if y_value < 0.0:
-						continue  # STACKED: skip negative values for total calculation
-					total += y_value
-
-			var scale := 1.0
-			if _bar_config.stacked_normalization == TauBarConfig.StackedNormalization.FRACTION:
-				scale = 1.0 / total if total > 0.0 else 0.0
-			elif _bar_config.stacked_normalization == TauBarConfig.StackedNormalization.PERCENT:
-				scale = 100.0 / total if total > 0.0 else 0.0
-
-			# Compute segments for this X position in dataset order
-			var segments: Array = []
-			var accum := 0.0
-			for series_index in range(p_series_count):
-				var series_id := _get_bar_series_id(series_index)
-				var y_raw := _dataset.get_series_y(series_id, i)
-				if is_nan(y_raw) or is_inf(y_raw):
-					continue
-				if y_raw < 0.0:
-					continue  # STACKED: skip negative values
-
-				var y := y_raw * scale
-				var y0 := accum
-				var y1 := accum + y
-
-				segments.append({"series_index": series_index, "y0": y0, "y1": y1})
-				accum = y1
-
-			all_segments[i] = segments
+			all_segments[i] = _compute_stacked_segments_at(p_series_count, i)
 
 		# Second pass: paint in z_order (series first, then X positions)
 		var draw_order := _get_series_draw_order(p_series_count)
diff --git a/addons/tau-plot/plot/xy/bar/bar_validator.gd b/addons/tau-plot/plot/xy/bar/bar_validator.gd
index a829f55..ada08b7 100644
--- a/addons/tau-plot/plot/xy/bar/bar_validator.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_validator.gd
@@ -32,7 +32,7 @@ class BarValidator extends RefCounted:
 				p_result.add_error("BarValidator: binding has pane_index %d, expected %d" % [binding.pane_index, p_pane_index])
 				return
 			if binding.overlay_type != PaneOverlayType.BAR:
-				p_result.add_error("BarValidator: binding has overlay_type %d, expected BAR" % int(binding.overlay_type))
+				p_result.add_error("BarValidator: binding has overlay_type %d, expected BAR" % binding.overlay_type)
 				return
 
 		var pane_cfg := p_domain_cfg.panes[p_pane_index]
@@ -48,7 +48,7 @@ class BarValidator extends RefCounted:
 		_validate_bar_visuals(p_pane_index, bar_config, p_bar_overlay_bindings, p_result)
 
 		var is_shared_x := (p_dataset.get_mode() == Dataset.Mode.SHARED_X)
-		_validate_bar_mode_constraints(p_pane_index, bar_config.mode, pane_cfg, p_bar_overlay_bindings, is_shared_x, p_result)
+		_validate_bar_mode_constraints(p_pane_index, bar_config, pane_cfg, p_bar_overlay_bindings, is_shared_x, p_result)
 
 		var x_cfg := p_domain_cfg.x_axis
 		if x_cfg != null:
@@ -69,8 +69,8 @@ class BarValidator extends RefCounted:
 				p_result.add_error("BarValidator: pane %d: series_id %d has visual_attributes that is not a BarVisualAttributes" % [p_pane_index, binding.series_id])
 
 
-	static func _validate_bar_mode_constraints(p_pane_index: int, p_bar_mode: TauBarConfig.BarMode, p_pane_cfg: TauPaneConfig, p_bar_overlay_bindings: Array[TauXYSeriesBinding], p_is_shared_x: bool, p_result: ValidationResult) -> void:
-		match p_bar_mode:
+	static func _validate_bar_mode_constraints(p_pane_index: int, p_bar_config: TauBarConfig, p_pane_cfg: TauPaneConfig, p_bar_overlay_bindings: Array[TauXYSeriesBinding], p_is_shared_x: bool, p_result: ValidationResult) -> void:
+		match p_bar_config.mode:
 			TauBarConfig.BarMode.GROUPED:
 				if not p_is_shared_x:
 					p_result.add_error("BarValidator: pane %d: GROUPED mode requires SHARED_X dataset mode" % p_pane_index)
@@ -79,6 +79,11 @@ class BarValidator extends RefCounted:
 				if not p_is_shared_x:
 					p_result.add_error("BarValidator: pane %d: STACKED mode requires SHARED_X dataset mode" % p_pane_index)
 
+				# SIGNED_SUM is geometrically incompatible with bar STACKED:
+				# negative contributions would require subtracting from the cumulative, which produces overlapping rectangles.
+				if p_bar_config.stacked_negative_policy == TauBarConfig.StackedNegativePolicy.SIGNED_SUM:
+					p_result.add_error("BarValidator: pane %d: STACKED mode does not support SIGNED_SUM negative policy. Use DIVERGING or SKIP_NEGATIVES." % p_pane_index)
+
 				if not p_bar_overlay_bindings.is_empty():
 					# All stacked bar series must share the same y axis.
 					var first_y_axis_id := p_bar_overlay_bindings[0].y_axis_id
@@ -95,7 +100,7 @@ class BarValidator extends RefCounted:
 				pass  # No mode-specific constraints
 
 			_:
-				p_result.add_error("BarValidator: pane %d: unsupported bar mode %d" % [p_pane_index, int(p_bar_mode)])
+				p_result.add_error("BarValidator: pane %d: unsupported bar mode %d" % [p_pane_index, p_bar_config.mode])
 
 
 	static func _validate_bar_width_config(p_pane_index: int, p_x_axis_cfg: TauAxisConfig, p_bar_config: TauBarConfig, p_result: ValidationResult) -> void:
@@ -112,17 +117,17 @@ class BarValidator extends RefCounted:
 					TauBarConfig.BarWidthPolicy.THEME, TauBarConfig.BarWidthPolicy.CATEGORY_WIDTH_FRACTION:
 						pass
 					_:
-						p_result.add_error("BarValidator: pane %d: bar_width_policy %d is not allowed for CATEGORICAL x-axis" % [p_pane_index, int(p_policy)])
+						p_result.add_error("BarValidator: pane %d: bar_width_policy %d is not allowed for CATEGORICAL x-axis" % [p_pane_index, p_policy])
 
 			TauAxisConfig.Type.CONTINUOUS:
 				match p_policy:
 					TauBarConfig.BarWidthPolicy.THEME, TauBarConfig.BarWidthPolicy.DATA_UNITS, TauBarConfig.BarWidthPolicy.NEIGHBOR_SPACING_FRACTION:
 						pass
 					_:
-						p_result.add_error("BarValidator: pane %d: bar_width_policy %d is not allowed for CONTINUOUS x-axis" % [p_pane_index, int(p_policy)])
+						p_result.add_error("BarValidator: pane %d: bar_width_policy %d is not allowed for CONTINUOUS x-axis" % [p_pane_index, p_policy])
 
 			_:
-				p_result.add_error("BarValidator: pane %d: unexpected x-axis type %d" % [p_pane_index, int(p_x_axis_type)])
+				p_result.add_error("BarValidator: pane %d: unexpected x-axis type %d" % [p_pane_index, p_x_axis_type])
 
 
 	static func _validate_bar_width_policy_params(p_pane_index: int, p_x_axis_scale: TauAxisConfig.Scale, p_policy: TauBarConfig.BarWidthPolicy, p_bar_config: TauBarConfig, p_result: ValidationResult) -> void:
@@ -163,4 +168,4 @@ class BarValidator extends RefCounted:
 						p_result.add_error("BarValidator: pane %d: neighbor_gap_fraction must be >= 0 (got %f)" % [p_pane_index, p_bar_config.neighbor_gap_fraction])
 
 			_:
-				p_result.add_error("BarValidator: pane %d: unsupported bar_width_policy %d" % [p_pane_index, int(p_policy)])
+				p_result.add_error("BarValidator: pane %d: unsupported bar_width_policy %d" % [p_pane_index, p_policy])
diff --git a/addons/tau-plot/plot/xy/line/line_config.gd b/addons/tau-plot/plot/xy/line/line_config.gd
index 2424ad4..e9e362b 100644
--- a/addons/tau-plot/plot/xy/line/line_config.gd
+++ b/addons/tau-plot/plot/xy/line/line_config.gd
@@ -23,6 +23,15 @@ enum LineMode
 const StackedNormalization = preload("res://addons/tau-plot/plot/xy/stacked_normalization.gd").StackedNormalization
 @export var stacked_normalization: StackedNormalization = StackedNormalization.NONE
 
+const StackedNegativePolicy = preload("res://addons/tau-plot/plot/xy/stacked_negative_policy.gd").StackedNegativePolicy
+
+## How negative values are handled in STACKED mode.
+## SIGNED_SUM (default) folds negative values into the cumulative as a downward
+## dip, the streamgraph behavior. DIVERGING splits each X into an upper stack
+## of positive values and a lower stack of negative values, both anchored at
+## zero. SKIP_NEGATIVES drops negative samples entirely from the stack.
+@export var stacked_negative_policy: StackedNegativePolicy = StackedNegativePolicy.SIGNED_SUM
+
 ## Strategy applied when the curve encounters a sample with a NaN or infinite
 ## X or Y value (or a value forbidden by the active axis scale, such as a
 ## non-positive value on a logarithmic axis).
@@ -115,6 +124,8 @@ func is_equal_to(p_other: TauPaneOverlayConfig) -> bool:
 		return false
 	if stacked_normalization != other.stacked_normalization:
 		return false
+	if stacked_negative_policy != other.stacked_negative_policy:
+		return false
 	if gap_policy != other.gap_policy:
 		return false
 	if interpolation_mode != other.interpolation_mode:
@@ -128,8 +139,10 @@ func is_equal_to(p_other: TauPaneOverlayConfig) -> bool:
 # Returns true if the change between this and p_other affects layout/domain.
 # Returns false if the change only affects visual appearance.
 #
-# Only mode and stacked_normalization affect the domain: stacking changes the
-# Y bounds. Hover distance is a pure hit-test parameter with no layout effect.
+# mode, stacked_normalization, and stacked_negative_policy affect the domain:
+# stacking changes Y bounds, normalization pins the range, and the negative
+# policy decides whether the lower half-axis exists. Hover distance is a pure
+# hit-test parameter with no layout effect.
 func has_layout_affecting_change(p_other: TauPaneOverlayConfig) -> bool:
 	var other := p_other as TauLineConfig
 	if other == null:
@@ -144,4 +157,7 @@ func has_layout_affecting_change(p_other: TauPaneOverlayConfig) -> bool:
 	if mode == LineMode.STACKED and stacked_normalization != other.stacked_normalization:
 		return true
 
+	if mode == LineMode.STACKED and stacked_negative_policy != other.stacked_negative_policy:
+		return true
+
 	return false
diff --git a/addons/tau-plot/plot/xy/stacked_negative_policy.gd b/addons/tau-plot/plot/xy/stacked_negative_policy.gd
new file mode 100644
index 0000000..e81be3a
--- /dev/null
+++ b/addons/tau-plot/plot/xy/stacked_negative_policy.gd
@@ -0,0 +1,12 @@
+enum StackedNegativePolicy
+{
+	DIVERGING,        ## Positive values stack upward from zero, negative values stack
+					  ## downward from zero. Two independent cumulatives per X.
+
+	SIGNED_SUM,       ## Negative values are summed signed into the cumulative.
+					  ## A negative contribution causes the cumulative to dip below
+					  ## the previous layer.
+
+	SKIP_NEGATIVES    ## Negative values are dropped from the cumulative. The sample
+					  ## is treated as if its value were zero for stacking purposes.
+}
diff --git a/addons/tau-plot/plot/xy/stacked_negative_policy.gd.uid b/addons/tau-plot/plot/xy/stacked_negative_policy.gd.uid
new file mode 100644
index 0000000..2c351bf
--- /dev/null
+++ b/addons/tau-plot/plot/xy/stacked_negative_policy.gd.uid
@@ -0,0 +1 @@
+uid://bbq86jgmtfkyu
diff --git a/addons/tau-plot/plot/xy/stacked_pinned_range.gd b/addons/tau-plot/plot/xy/stacked_pinned_range.gd
new file mode 100644
index 0000000..5c7cffc
--- /dev/null
+++ b/addons/tau-plot/plot/xy/stacked_pinned_range.gd
@@ -0,0 +1,31 @@
+const StackedNormalization = preload("res://addons/tau-plot/plot/xy/stacked_normalization.gd").StackedNormalization
+const StackedNegativePolicy = preload("res://addons/tau-plot/plot/xy/stacked_negative_policy.gd").StackedNegativePolicy
+
+
+## Computes the pinned Y axis range that a stacked overlay imposes on its
+## target axis, given the active normalization and negative policy.
+##
+## NONE normalization does not pin the range: the axis is computed from the
+## stacked data itself by the domain scanner. Returns Vector2.ZERO and the
+## caller is expected to ignore the result when normalization is NONE.
+##
+## FRACTION and PERCENT pin the range so that every per-X stack fits exactly:
+## SKIP_NEGATIVES yields [0, 1] / [0, 100], the diverging and signed_sum
+## policies need both half-axes and yield [-1, 1] / [-100, 100].
+class StackedPinnedRange extends RefCounted:
+
+	## Returns the (min, max) pinned range. Caller decides whether to apply it
+	## based on normalization (NONE means no pinning).
+	static func compute(p_normalization: StackedNormalization, p_policy: StackedNegativePolicy) -> Vector2:
+		match p_normalization:
+			StackedNormalization.FRACTION:
+				if p_policy == StackedNegativePolicy.SKIP_NEGATIVES:
+					return Vector2(0.0, 1.0)
+				return Vector2(-1.0, 1.0)
+
+			StackedNormalization.PERCENT:
+				if p_policy == StackedNegativePolicy.SKIP_NEGATIVES:
+					return Vector2(0.0, 100.0)
+				return Vector2(-100.0, 100.0)
+
+		return Vector2.ZERO
diff --git a/addons/tau-plot/plot/xy/stacked_pinned_range.gd.uid b/addons/tau-plot/plot/xy/stacked_pinned_range.gd.uid
new file mode 100644
index 0000000..8a3faa2
--- /dev/null
+++ b/addons/tau-plot/plot/xy/stacked_pinned_range.gd.uid
@@ -0,0 +1 @@
+uid://dtqwlm0r8gpw7
diff --git a/addons/tau-plot/plot/xy/xy_plot.gd b/addons/tau-plot/plot/xy/xy_plot.gd
index 3df5348..8e99409 100644
--- a/addons/tau-plot/plot/xy/xy_plot.gd
+++ b/addons/tau-plot/plot/xy/xy_plot.gd
@@ -23,6 +23,7 @@ const XYState := preload("res://addons/tau-plot/plot/xy/xy_state.gd").XYState
 const XYDomain := preload("res://addons/tau-plot/plot/xy/xy_domain.gd").XYDomain
 const XYDomainOverrides := preload("res://addons/tau-plot/plot/xy/xy_domain_overrides.gd").XYDomainOverrides
 const YDomainOverride := preload("res://addons/tau-plot/plot/xy/xy_domain_overrides.gd").YDomainOverride
+const StackedPinnedRange := preload("res://addons/tau-plot/plot/xy/stacked_pinned_range.gd").StackedPinnedRange
 const XYLayout := preload("res://addons/tau-plot/plot/xy/xy_layout.gd").XYLayout
 const XYAxisTitleLayout := preload("res://addons/tau-plot/plot/xy/xy_axis_title_layout.gd").XYAxisTitleLayout
 const VisualAttributes = preload("res://addons/tau-plot/plot/xy/visual_attributes.gd").VisualAttributes
@@ -1184,15 +1185,11 @@ func _apply_bar_domain_overrides_y() -> void:
 			TauBarConfig.StackedNormalization.NONE:
 				y_domain_override.stack_y_values = true
 
-			TauBarConfig.StackedNormalization.FRACTION:
+			TauBarConfig.StackedNormalization.FRACTION, TauBarConfig.StackedNormalization.PERCENT:
+				var pinned := StackedPinnedRange.compute(pane_bar_config.stacked_normalization, pane_bar_config.stacked_negative_policy)
 				y_domain_override.force_y_range = true
-				y_domain_override.force_y_min = 0.0
-				y_domain_override.force_y_max = 1.0
-
-			TauBarConfig.StackedNormalization.PERCENT:
-				y_domain_override.force_y_range = true
-				y_domain_override.force_y_min = 0.0
-				y_domain_override.force_y_max = 100.0
+				y_domain_override.force_y_min = pinned.x
+				y_domain_override.force_y_max = pinned.y
 
 			_:
 				push_error("_apply_bar_domain_overrides_y(): unexpected stacked normalization")

From 6f9576e4c0a8278fed35718b25ba97e43c267805 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Tue, 5 May 2026 23:02:56 +0200
Subject: [PATCH 18/23] Per-axis domain override storage

---
 .../plot/xy/dataset_change_analyzer.gd        |  6 +--
 addons/tau-plot/plot/xy/xy_domain.gd          | 30 ++++++------
 .../tau-plot/plot/xy/xy_domain_overrides.gd   | 48 ++++++++++++++-----
 addons/tau-plot/plot/xy/xy_plot.gd            |  9 ++--
 4 files changed, 57 insertions(+), 36 deletions(-)

diff --git a/addons/tau-plot/plot/xy/dataset_change_analyzer.gd b/addons/tau-plot/plot/xy/dataset_change_analyzer.gd
index ba8441b..9093652 100644
--- a/addons/tau-plot/plot/xy/dataset_change_analyzer.gd
+++ b/addons/tau-plot/plot/xy/dataset_change_analyzer.gd
@@ -113,9 +113,9 @@ class DatasetChangeAnalyzer extends RefCounted:
 					if axis_domain.config != null and axis_domain.config.range_override_enabled:
 						continue
 
-					# Bar stacking override (FRACTION/PERCENT) pins the range on the target axis.
-					var pane_override: YDomainOverride = p_domain_overrides.y_domain_overrides[pane_idx]
-					if pane_override.force_y_range and pane_override.target_y_axis_id == y_axis_id:
+					# A stacking override (FRACTION/PERCENT) on this axis pins the range.
+					var pane_override: YDomainOverride = p_domain_overrides.get_override(pane_idx, y_axis_id)
+					if pane_override != null and pane_override.force_y_range:
 						continue
 
 					# include_zero could shift bounds even if the new values are in range.
diff --git a/addons/tau-plot/plot/xy/xy_domain.gd b/addons/tau-plot/plot/xy/xy_domain.gd
index 3e6d82e..c1f6197 100644
--- a/addons/tau-plot/plot/xy/xy_domain.gd
+++ b/addons/tau-plot/plot/xy/xy_domain.gd
@@ -249,8 +249,8 @@ class XYDomain extends RefCounted:
 
 			var y_range_forced := _is_y_range_forced(p_pane_idx, y_axis_id)
 			if y_range_forced:
-				y_axis_domain.min_val = _get_forced_y_min(p_pane_idx)
-				y_axis_domain.max_val = _get_forced_y_max(p_pane_idx)
+				y_axis_domain.min_val = _get_forced_y_min(p_pane_idx, y_axis_id)
+				y_axis_domain.max_val = _get_forced_y_max(p_pane_idx, y_axis_id)
 			else:
 				var final_range := _finalize_y_axis_domain(y_axis_domain)
 				y_axis_domain.min_val = final_range.x
@@ -356,35 +356,37 @@ class XYDomain extends RefCounted:
 	func _is_y_range_forced(p_pane_index: int, p_y_axis_id: AxisId) -> bool:
 		if overrides == null:
 			return false
-		if p_pane_index < 0 or p_pane_index >= overrides.y_domain_overrides.size():
+		var ydo := overrides.get_override(p_pane_index, p_y_axis_id)
+		if ydo == null:
 			return false
-		var ydo := overrides.y_domain_overrides[p_pane_index]
-		return ydo.force_y_range and ydo.target_y_axis_id == p_y_axis_id
+		return ydo.force_y_range
 
 
-	func _get_forced_y_min(p_pane_index: int) -> float:
+	func _get_forced_y_min(p_pane_index: int, p_y_axis_id: AxisId) -> float:
 		if overrides == null:
 			return 0.0
-		if p_pane_index < 0 or p_pane_index >= overrides.y_domain_overrides.size():
+		var ydo := overrides.get_override(p_pane_index, p_y_axis_id)
+		if ydo == null:
 			return 0.0
-		return overrides.y_domain_overrides[p_pane_index].force_y_min
+		return ydo.force_y_min
 
 
-	func _get_forced_y_max(p_pane_index: int) -> float:
+	func _get_forced_y_max(p_pane_index: int, p_y_axis_id: AxisId) -> float:
 		if overrides == null:
 			return 1.0
-		if p_pane_index < 0 or p_pane_index >= overrides.y_domain_overrides.size():
+		var ydo := overrides.get_override(p_pane_index, p_y_axis_id)
+		if ydo == null:
 			return 1.0
-		return overrides.y_domain_overrides[p_pane_index].force_y_max
+		return ydo.force_y_max
 
 
 	func _must_stack_y_values(p_pane_index: int, p_y_axis_id: AxisId) -> bool:
 		if overrides == null:
 			return false
-		if p_pane_index < 0 or p_pane_index >= overrides.y_domain_overrides.size():
+		var ydo := overrides.get_override(p_pane_index, p_y_axis_id)
+		if ydo == null:
 			return false
-		var ydo := overrides.y_domain_overrides[p_pane_index]
-		return ydo.stack_y_values and ydo.target_y_axis_id == p_y_axis_id
+		return ydo.stack_y_values
 
 
 	func _scan_series_y_range(p_dataset: Dataset, p_y_axis_series_ids: PackedInt64Array, p_pane_idx: int, p_y_axis_id: AxisId, p_is_log: bool) -> Vector2:
diff --git a/addons/tau-plot/plot/xy/xy_domain_overrides.gd b/addons/tau-plot/plot/xy/xy_domain_overrides.gd
index 9242ca3..ea73630 100644
--- a/addons/tau-plot/plot/xy/xy_domain_overrides.gd
+++ b/addons/tau-plot/plot/xy/xy_domain_overrides.gd
@@ -1,10 +1,8 @@
-class YDomainOverride extends RefCounted:
-	const AxisId = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").AxisId
+const AxisId = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").AxisId
+
 
-	# The y-axis that the override targets. Only that axis is affected by
-	# force_y_range and stack_y_values. A value of -1 means "no axis targeted"
-	# (override is inactive regardless of the flags above).
-	var target_y_axis_id: int = -1
+# Stacking and forced-range override for one (pane, y-axis) pair.
+class YDomainOverride extends RefCounted:
 
 	var force_y_range: bool = false
 	var force_y_min: float = 0.0
@@ -14,23 +12,47 @@ class YDomainOverride extends RefCounted:
 
 
 	func reset() -> void:
-		target_y_axis_id = -1
 		force_y_range = false
 		force_y_min = 0.0
 		force_y_max = 1.0
 		stack_y_values = false
 
 
-# XY plot domain overrides driven by renderers.
-# Y axis overrides are per-pane.
+# Per-pane and per-axis Y domain overrides driven by renderers.
 class XYDomainOverrides extends RefCounted:
 
-	var y_domain_overrides: Array[YDomainOverride] = [] # Per-pane Y axis overrides.
+	var y_domain_overrides: Array = [] # FIXME Real type is Array[Dictionary[AxisId, YDomainOverride]. Godot 4.5 does not support nested typed collections.
 
-	# Initializes per-pane override storage. Existing entries are preserved up to
-	# p_pane_count. Excess entries are trimmed and missing entries are appended.
+
+	# Resizes per-pane storage. Existing entries below p_pane_count are kept.
 	func init_panes(p_pane_count: int) -> void:
 		while y_domain_overrides.size() > p_pane_count:
 			y_domain_overrides.pop_back()
 		while y_domain_overrides.size() < p_pane_count:
-			y_domain_overrides.append(YDomainOverride.new())
+			var empty: Dictionary[AxisId, YDomainOverride] = {}
+			y_domain_overrides.append(empty)
+
+
+	# Returns null when no override exists for that (pane, axis).
+	func get_override(p_pane_index: int, p_y_axis_id: AxisId) -> YDomainOverride:
+		if p_pane_index < 0 or p_pane_index >= y_domain_overrides.size():
+			return null
+		var pane_dict: Dictionary[AxisId, YDomainOverride] = y_domain_overrides[p_pane_index]
+		if p_y_axis_id in pane_dict:
+			return pane_dict[p_y_axis_id]
+		return null
+
+
+	func get_or_create_override(p_pane_index: int, p_y_axis_id: AxisId) -> YDomainOverride:
+		var pane_dict: Dictionary[AxisId, YDomainOverride] = y_domain_overrides[p_pane_index]
+		if p_y_axis_id in pane_dict:
+			return pane_dict[p_y_axis_id]
+		var override := YDomainOverride.new()
+		pane_dict[p_y_axis_id] = override
+		return override
+
+
+	func clear_pane(p_pane_index: int) -> void:
+		if p_pane_index < 0 or p_pane_index >= y_domain_overrides.size():
+			return
+		y_domain_overrides[p_pane_index].clear()
diff --git a/addons/tau-plot/plot/xy/xy_plot.gd b/addons/tau-plot/plot/xy/xy_plot.gd
index 8e99409..66abd8f 100644
--- a/addons/tau-plot/plot/xy/xy_plot.gd
+++ b/addons/tau-plot/plot/xy/xy_plot.gd
@@ -1148,6 +1148,8 @@ func _update_xy_layout(p_pane_view_rects: Array[Rect2], p_pane_positions: Array[
 func _apply_bar_domain_overrides_y() -> void:
 	var pane_count := _domain_config.panes.size()
 	for pane_index in range(pane_count):
+		_xy_domain_overrides.clear_pane(pane_index)
+
 		if pane_index >= _bar_series_ids_per_pane.size():
 			continue
 		if _bar_series_ids_per_pane[pane_index].is_empty():
@@ -1157,11 +1159,6 @@ func _apply_bar_domain_overrides_y() -> void:
 		if pane_bar_config == null:
 			continue
 
-		var y_domain_override: YDomainOverride = _xy_domain_overrides.y_domain_overrides[pane_index]
-
-		# Reset vertical overrides each recompute then re-apply if needed.
-		y_domain_override.reset()
-
 		if pane_bar_config.mode != TauBarConfig.BarMode.STACKED:
 			continue
 
@@ -1179,7 +1176,7 @@ func _apply_bar_domain_overrides_y() -> void:
 		if stacked_y_cfg != null and stacked_y_cfg.range_override_enabled:
 			continue
 
-		y_domain_override.target_y_axis_id = stacked_y_axis_id
+		var y_domain_override: YDomainOverride = _xy_domain_overrides.get_or_create_override(pane_index, stacked_y_axis_id)
 
 		match pane_bar_config.stacked_normalization:
 			TauBarConfig.StackedNormalization.NONE:

From 70a83cffbb3fcf72c0a572ebd1b921542847a9e6 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Wed, 6 May 2026 07:13:22 +0100
Subject: [PATCH 19/23] Fix domain computation of stacked series

---
 addons/tau-plot/plot/xy/xy_domain.gd          | 190 ++++++++++++++----
 .../tau-plot/plot/xy/xy_domain_overrides.gd   |  21 +-
 addons/tau-plot/plot/xy/xy_plot.gd            |   9 +-
 3 files changed, 175 insertions(+), 45 deletions(-)

diff --git a/addons/tau-plot/plot/xy/xy_domain.gd b/addons/tau-plot/plot/xy/xy_domain.gd
index c1f6197..4918d48 100644
--- a/addons/tau-plot/plot/xy/xy_domain.gd
+++ b/addons/tau-plot/plot/xy/xy_domain.gd
@@ -5,6 +5,7 @@ const XYDomainOverrides := preload("res://addons/tau-plot/plot/xy/xy_domain_over
 const SeriesAxisAssignment := preload("res://addons/tau-plot/plot/xy/series_axis_assignment.gd").SeriesAxisAssignment
 const AxisId = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").AxisId
 const Axis = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").Axis
+const StackedNegativePolicy = preload("res://addons/tau-plot/plot/xy/stacked_negative_policy.gd").StackedNegativePolicy
 
 
 # Resolved domain for a single axis.
@@ -66,6 +67,10 @@ class XYDomain extends RefCounted:
 	var overrides: XYDomainOverrides = null
 	var series_assignment: SeriesAxisAssignment = null
 
+	# Per-pane series ids.
+	var bar_series_ids_per_pane: Array[PackedInt64Array] = []
+	var line_series_ids_per_pane: Array[PackedInt64Array] = []
+
 	# Outputs
 	var x_axis_domain: AxisDomain = AxisDomain.new()
 	var x_categories: PackedStringArray = []
@@ -77,10 +82,15 @@ class XYDomain extends RefCounted:
 	const _LOG_MIN_DOMAIN_RATIO: float = 1.1  # Minimum ratio between max/min for log scales
 
 
-	func _init(p_dataset: Dataset, p_config: TauXYConfig, p_series_assignment: SeriesAxisAssignment, p_overrides: XYDomainOverrides = null) -> void:
+	func _init(p_dataset: Dataset, p_config: TauXYConfig, p_series_assignment: SeriesAxisAssignment,
+				p_bar_series_ids_per_pane: Array[PackedInt64Array],
+				p_line_series_ids_per_pane: Array[PackedInt64Array],
+				p_overrides: XYDomainOverrides) -> void:
 		config = p_config
 		overrides = p_overrides
 		series_assignment = p_series_assignment
+		bar_series_ids_per_pane = p_bar_series_ids_per_pane
+		line_series_ids_per_pane = p_line_series_ids_per_pane
 		update_from_dataset(p_dataset)
 
 
@@ -354,8 +364,6 @@ class XYDomain extends RefCounted:
 
 
 	func _is_y_range_forced(p_pane_index: int, p_y_axis_id: AxisId) -> bool:
-		if overrides == null:
-			return false
 		var ydo := overrides.get_override(p_pane_index, p_y_axis_id)
 		if ydo == null:
 			return false
@@ -363,8 +371,6 @@ class XYDomain extends RefCounted:
 
 
 	func _get_forced_y_min(p_pane_index: int, p_y_axis_id: AxisId) -> float:
-		if overrides == null:
-			return 0.0
 		var ydo := overrides.get_override(p_pane_index, p_y_axis_id)
 		if ydo == null:
 			return 0.0
@@ -372,37 +378,50 @@ class XYDomain extends RefCounted:
 
 
 	func _get_forced_y_max(p_pane_index: int, p_y_axis_id: AxisId) -> float:
-		if overrides == null:
-			return 1.0
 		var ydo := overrides.get_override(p_pane_index, p_y_axis_id)
 		if ydo == null:
 			return 1.0
 		return ydo.force_y_max
 
 
-	func _must_stack_y_values(p_pane_index: int, p_y_axis_id: AxisId) -> bool:
-		if overrides == null:
-			return false
-		var ydo := overrides.get_override(p_pane_index, p_y_axis_id)
-		if ydo == null:
-			return false
-		return ydo.stack_y_values
+	# Series on the axis are partitioned into three groups: bar-stacked,
+	# line-stacked, and non-stacked. Each group contributes a Y range computed
+	# in isolation, and the axis range is the union of the three. When two
+	# stacked overlay types target the same axis the validator guarantees they
+	# share normalization and negative policy.
+	func _scan_series_y_range(p_dataset: Dataset, p_y_axis_series_ids: PackedInt64Array, p_pane_idx: int, p_y_axis_id: AxisId, p_is_log: bool) -> Vector2:
+		var ydo: YDomainOverride = overrides.get_override(p_pane_idx, p_y_axis_id)
 
+		var bar_partition: PackedInt64Array
+		var line_partition: PackedInt64Array
+		if ydo != null and ydo.bar_stack_active:
+			bar_partition = _intersect_with_pane_partition(p_y_axis_series_ids, bar_series_ids_per_pane, p_pane_idx)
+		if ydo != null and ydo.line_stack_active:
+			line_partition = _intersect_with_pane_partition(p_y_axis_series_ids, line_series_ids_per_pane, p_pane_idx)
 
-	func _scan_series_y_range(p_dataset: Dataset, p_y_axis_series_ids: PackedInt64Array, p_pane_idx: int, p_y_axis_id: AxisId, p_is_log: bool) -> Vector2:
+		var non_stacked := _subtract_partitions(p_y_axis_series_ids, bar_partition, line_partition)
+
+		var range_acc := Vector2(INF, -INF)
+		range_acc = _union_range(range_acc, _scan_independent(p_dataset, non_stacked, p_is_log))
+
+		if not bar_partition.is_empty():
+			range_acc = _union_range(range_acc, _scan_stacked(p_dataset, bar_partition, ydo.stacked_negative_policy, p_is_log))
+		if not line_partition.is_empty():
+			range_acc = _union_range(range_acc, _scan_stacked(p_dataset, line_partition, ydo.stacked_negative_policy, p_is_log))
+
+		return range_acc
+
+
+	# Independent (per-series) min/max scan: each sample contributes on its own.
+	# Honors the per-dataset-mode iteration shape.
+	func _scan_independent(p_dataset: Dataset, p_series_ids: PackedInt64Array, p_is_log: bool) -> Vector2:
 		var y_min := INF
 		var y_max := -INF
 
 		match p_dataset.get_mode():
 			Dataset.Mode.SHARED_X:
-				for series_id in p_y_axis_series_ids:
-					if not p_dataset.has_series(series_id):
-						continue
-
-					if _must_stack_y_values(p_pane_idx, p_y_axis_id):
-						return _scan_stacked_series_y_range(p_dataset, p_y_axis_series_ids, p_is_log)
-
-					var sample_count := p_dataset.get_shared_sample_count()
+				var sample_count := p_dataset.get_shared_sample_count()
+				for series_id in p_series_ids:
 					for sample_index in range(sample_count):
 						var y_value := p_dataset.get_series_y(series_id, sample_index)
 						if is_nan(y_value) or is_inf(y_value):
@@ -413,10 +432,7 @@ class XYDomain extends RefCounted:
 						y_max = maxf(y_max, y_value)
 
 			Dataset.Mode.PER_SERIES_X:
-				for series_id in p_y_axis_series_ids:
-					if not p_dataset.has_series(series_id):
-						continue
-
+				for series_id in p_series_ids:
 					var sample_count := p_dataset.get_series_sample_count(series_id)
 					for sample_index in range(sample_count):
 						var y_value := p_dataset.get_series_y(series_id, sample_index)
@@ -430,29 +446,133 @@ class XYDomain extends RefCounted:
 		return Vector2(y_min, y_max)
 
 
-	func _scan_stacked_series_y_range(p_dataset: Dataset, p_y_axis_series_ids: PackedInt64Array, p_is_log: bool) -> Vector2:
+	func _scan_stacked(p_dataset: Dataset, p_series_ids: PackedInt64Array, p_policy: StackedNegativePolicy, p_is_log: bool) -> Vector2:
+		match p_policy:
+			StackedNegativePolicy.SKIP_NEGATIVES:
+				return _scan_stacked_skip_negatives(p_dataset, p_series_ids, p_policy, p_is_log)
+
+			StackedNegativePolicy.DIVERGING:
+				return _scan_stacked_diverging(p_dataset, p_series_ids, p_policy, p_is_log)
+
+			StackedNegativePolicy.SIGNED_SUM:
+				return _scan_stacked_signed_sum(p_dataset, p_series_ids, p_policy, p_is_log)
+
+			_:
+				push_error("Unexpected StackedNegativePolicy: %d" % p_policy)
+				return Vector2()
+
+
+	func _scan_stacked_skip_negatives(p_dataset: Dataset, p_series_ids: PackedInt64Array, p_policy: StackedNegativePolicy, p_is_log: bool) -> Vector2:
+		var y_min := INF
+		var y_max := -INF
+		var sample_count := p_dataset.get_shared_sample_count()
+
+		for sample_index in range(sample_count):
+			var pos_total := 0.0
+
+			for series_id in p_series_ids:
+				var y_value := p_dataset.get_series_y(series_id, sample_index)
+				if is_nan(y_value) or is_inf(y_value):
+					continue
+				if p_is_log and y_value <= 0.0:
+					continue
+
+				# SKIP_NEGATIVES
+				if y_value >= 0.0:
+					pos_total += y_value
+
+			# SKIP_NEGATIVES
+			y_min = minf(y_min, 0.0)
+			y_max = maxf(y_max, pos_total)
+
+		return Vector2(y_min, y_max)
+
+
+	func _scan_stacked_diverging(p_dataset: Dataset, p_series_ids: PackedInt64Array, p_policy: StackedNegativePolicy, p_is_log: bool) -> Vector2:
 		var y_min := INF
 		var y_max := -INF
 		var sample_count := p_dataset.get_shared_sample_count()
 
 		for sample_index in range(sample_count):
-			var sum := 0.0
-			for series_id in p_y_axis_series_ids:
-				if not p_dataset.has_series(series_id):
+			var pos_total := 0.0
+			var neg_total := 0.0
+
+			for series_id in p_series_ids:
+				var y_value := p_dataset.get_series_y(series_id, sample_index)
+				if is_nan(y_value) or is_inf(y_value):
+					continue
+				if p_is_log and y_value <= 0.0:
 					continue
 
+				# DIVERGING
+				if y_value >= 0.0:
+					pos_total += y_value
+				else:
+					neg_total += y_value
+
+			# DIVERGING
+			y_min = minf(y_min, neg_total)
+			y_max = maxf(y_max, pos_total)
+
+		return Vector2(y_min, y_max)
+
+
+	func _scan_stacked_signed_sum(p_dataset: Dataset, p_series_ids: PackedInt64Array, p_policy: StackedNegativePolicy, p_is_log: bool) -> Vector2:
+		var y_min := INF
+		var y_max := -INF
+		var sample_count := p_dataset.get_shared_sample_count()
+
+		for sample_index in range(sample_count):
+			var signed_running := 0.0
+			var signed_min_at_x := INF
+			var signed_max_at_x := -INF
+
+			for series_id in p_series_ids:
 				var y_value := p_dataset.get_series_y(series_id, sample_index)
 				if is_nan(y_value) or is_inf(y_value):
 					continue
 				if p_is_log and y_value <= 0.0:
 					continue
-				sum += y_value
-			y_min = minf(y_min, sum)
-			y_max = maxf(y_max, sum)
+
+				# SIGNED_SUM
+				signed_running += y_value
+				signed_min_at_x = minf(signed_min_at_x, signed_running)
+				signed_max_at_x = maxf(signed_max_at_x, signed_running)
+
+			# SIGNED_SUM
+			if signed_min_at_x != INF:
+				y_min = minf(y_min, signed_min_at_x)
+				y_max = maxf(y_max, signed_max_at_x)
 
 		return Vector2(y_min, y_max)
 
 
+	static func _intersect_with_pane_partition(p_axis_series_ids: PackedInt64Array,
+				p_partition_per_pane: Array[PackedInt64Array], p_pane_idx: int) -> PackedInt64Array:
+		var out := PackedInt64Array()
+		if p_pane_idx >= p_partition_per_pane.size():
+			return out
+		var partition: PackedInt64Array = p_partition_per_pane[p_pane_idx]
+		for sid in p_axis_series_ids:
+			if sid in partition:
+				out.append(sid)
+		return out
+
+
+	static func _subtract_partitions(p_axis_series_ids: PackedInt64Array,
+				p_a: PackedInt64Array, p_b: PackedInt64Array) -> PackedInt64Array:
+		var out := PackedInt64Array()
+		for sid in p_axis_series_ids:
+			if sid in p_a or sid in p_b:
+				continue
+			out.append(sid)
+		return out
+
+
+	static func _union_range(p_a: Vector2, p_b: Vector2) -> Vector2:
+		return Vector2(minf(p_a.x, p_b.x), maxf(p_a.y, p_b.y))
+
+
 	func _compute_continuous_shared_x(p_dataset: Dataset, p_is_log: bool) -> Vector2:
 		var xmin := INF
 		var xmax := -INF
@@ -473,8 +593,6 @@ class XYDomain extends RefCounted:
 		var xmax := -INF
 		for series_id_v in p_series_ids:
 			var series_id := series_id_v
-			if not p_dataset.has_series(series_id):
-				continue
 			var sample_count := p_dataset.get_series_sample_count(series_id)
 			for sample_index in range(sample_count):
 				var x_value := float(p_dataset.get_series_x(series_id, sample_index))
diff --git a/addons/tau-plot/plot/xy/xy_domain_overrides.gd b/addons/tau-plot/plot/xy/xy_domain_overrides.gd
index ea73630..8224277 100644
--- a/addons/tau-plot/plot/xy/xy_domain_overrides.gd
+++ b/addons/tau-plot/plot/xy/xy_domain_overrides.gd
@@ -1,21 +1,28 @@
 const AxisId = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").AxisId
+const StackedNormalization = preload("res://addons/tau-plot/plot/xy/stacked_normalization.gd").StackedNormalization
+const StackedNegativePolicy = preload("res://addons/tau-plot/plot/xy/stacked_negative_policy.gd").StackedNegativePolicy
 
 
 # Stacking and forced-range override for one (pane, y-axis) pair.
+#
+# bar_stack_active and line_stack_active are independent flags: each tells the
+# domain scanner that the corresponding overlay type contributes a stacked
+# cumulative on this axis. Both can be true at the same time, in which case
+# their cumulatives are computed separately and unioned with the non-stacked
+# range. Cross-overlay validation enforces a single shared
+# stacked_normalization and a single shared stacked_negative_policy on the
+# axis when both flags are true.
 class YDomainOverride extends RefCounted:
 
 	var force_y_range: bool = false
 	var force_y_min: float = 0.0
 	var force_y_max: float = 1.0
 
-	var stack_y_values: bool = false
+	var bar_stack_active: bool = false
+	var line_stack_active: bool = false
 
-
-	func reset() -> void:
-		force_y_range = false
-		force_y_min = 0.0
-		force_y_max = 1.0
-		stack_y_values = false
+	var stacked_normalization: StackedNormalization = StackedNormalization.NONE
+	var stacked_negative_policy: StackedNegativePolicy = StackedNegativePolicy.DIVERGING
 
 
 # Per-pane and per-axis Y domain overrides driven by renderers.
diff --git a/addons/tau-plot/plot/xy/xy_plot.gd b/addons/tau-plot/plot/xy/xy_plot.gd
index 66abd8f..ce28090 100644
--- a/addons/tau-plot/plot/xy/xy_plot.gd
+++ b/addons/tau-plot/plot/xy/xy_plot.gd
@@ -242,7 +242,8 @@ func setup(
 	# Domain + layout creation
 	_xy_domain_overrides = XYDomainOverrides.new()
 	_xy_domain_overrides.init_panes(pane_count)
-	_xy_domain = XYDomain.new(_dataset, _domain_config, _series_assignment, _xy_domain_overrides)
+	_xy_domain = XYDomain.new(_dataset, _domain_config, _series_assignment,
+			_bar_series_ids_per_pane, _line_series_ids_per_pane, _xy_domain_overrides)
 	_xy_layout = XYLayout.new(_xy_domain)
 
 	# Connect style changed signals for programmatic mutation detection.
@@ -1178,9 +1179,13 @@ func _apply_bar_domain_overrides_y() -> void:
 
 		var y_domain_override: YDomainOverride = _xy_domain_overrides.get_or_create_override(pane_index, stacked_y_axis_id)
 
+		y_domain_override.bar_stack_active = true
+		y_domain_override.stacked_normalization = pane_bar_config.stacked_normalization
+		y_domain_override.stacked_negative_policy = pane_bar_config.stacked_negative_policy
+
 		match pane_bar_config.stacked_normalization:
 			TauBarConfig.StackedNormalization.NONE:
-				y_domain_override.stack_y_values = true
+				pass
 
 			TauBarConfig.StackedNormalization.FRACTION, TauBarConfig.StackedNormalization.PERCENT:
 				var pinned := StackedPinnedRange.compute(pane_bar_config.stacked_normalization, pane_bar_config.stacked_negative_policy)

From e965166a2361c3bd1dcb8e78761227c68d598927 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Wed, 6 May 2026 22:43:47 +0200
Subject: [PATCH 20/23] Validate stacked overlays

---
 .../tau-plot/plot/xy/line/line_validator.gd   | 32 +++++++
 addons/tau-plot/plot/xy/xy_plot_validator.gd  | 84 +++++++++++++++++++
 2 files changed, 116 insertions(+)

diff --git a/addons/tau-plot/plot/xy/line/line_validator.gd b/addons/tau-plot/plot/xy/line/line_validator.gd
index fc919d6..5488adc 100644
--- a/addons/tau-plot/plot/xy/line/line_validator.gd
+++ b/addons/tau-plot/plot/xy/line/line_validator.gd
@@ -1,6 +1,7 @@
 # Dependencies
 const Dataset := preload("res://addons/tau-plot/model/dataset.gd").Dataset
 const PaneOverlayType = preload("res://addons/tau-plot/plot/xy/pane_overlay_type.gd").PaneOverlayType
+const Axis = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").Axis
 const LineVisualAttributes = preload("res://addons/tau-plot/plot/xy/line/line_visual_attributes.gd").LineVisualAttributes
 const LineVisualCallbacks = preload("res://addons/tau-plot/plot/xy/line/line_visual_callbacks.gd").LineVisualCallbacks
 const ValidationResult = preload("res://addons/tau-plot/plot/validation_result.gd").ValidationResult
@@ -46,6 +47,9 @@ class LineValidator extends RefCounted:
 
 		_validate_line_visuals(p_pane_index, line_config, p_line_overlay_bindings, p_result)
 
+		var is_shared_x := (p_dataset.get_mode() == Dataset.Mode.SHARED_X)
+		_validate_line_mode_constraints(p_pane_index, line_config, pane_cfg, p_line_overlay_bindings, is_shared_x, p_result)
+
 
 	####################################################################################################
 	# Private
@@ -59,3 +63,31 @@ class LineValidator extends RefCounted:
 			var binding: TauXYSeriesBinding = p_line_overlay_bindings[i]
 			if binding.visual_attributes != null and binding.visual_attributes is not LineVisualAttributes:
 				p_result.add_error("LineValidator: pane %d: series_id %d has visual_attributes that is not a LineVisualAttributes" % [p_pane_index, binding.series_id])
+
+
+	static func _validate_line_mode_constraints(p_pane_index: int, p_line_config: TauLineConfig, p_pane_cfg: TauPaneConfig, p_line_overlay_bindings: Array[TauXYSeriesBinding], p_is_shared_x: bool, p_result: ValidationResult) -> void:
+		match p_line_config.mode:
+			TauLineConfig.LineMode.INDEPENDENT:
+				pass
+
+			TauLineConfig.LineMode.STACKED:
+				# STACKED computes a per-X cumulative across series, so all series
+				# must share aligned X positions.
+				if not p_is_shared_x:
+					p_result.add_error("LineValidator: pane %d: STACKED mode requires SHARED_X dataset mode" % p_pane_index)
+
+				if not p_line_overlay_bindings.is_empty():
+					# All stacked line series must share the same y axis.
+					var first_y_axis_id := p_line_overlay_bindings[0].y_axis_id
+					for i in range(1, p_line_overlay_bindings.size()):
+						var binding: TauXYSeriesBinding = p_line_overlay_bindings[i]
+						if binding.y_axis_id != first_y_axis_id:
+							p_result.add_error("LineValidator: pane %d: STACKED mode requires all line series on the same y axis, but series_id %d uses %s (expected %s)" % [p_pane_index, binding.series_id, Axis.as_string(binding.y_axis_id), Axis.as_string(first_y_axis_id)])
+
+					# Cumulative sums on a logarithmic axis are not meaningful.
+					var y_axis_config: TauAxisConfig = p_pane_cfg.get_y_axis_config(first_y_axis_id)
+					if y_axis_config != null and y_axis_config.scale == TauAxisConfig.Scale.LOGARITHMIC:
+						p_result.add_error("LineValidator: pane %d: STACKED mode is incompatible with logarithmic y axis" % p_pane_index)
+
+			_:
+				p_result.add_error("LineValidator: pane %d: unsupported line mode %d" % [p_pane_index, p_line_config.mode])
diff --git a/addons/tau-plot/plot/xy/xy_plot_validator.gd b/addons/tau-plot/plot/xy/xy_plot_validator.gd
index 4b6ab72..e9ec14b 100644
--- a/addons/tau-plot/plot/xy/xy_plot_validator.gd
+++ b/addons/tau-plot/plot/xy/xy_plot_validator.gd
@@ -57,6 +57,14 @@ class XYPlotValidator extends RefCounted:
 		if p_result.has_errors():
 			return false
 
+		# -- Cross-overlay stacking constraints --
+		# When two stacked overlays share a Y axis in the same pane, their
+		# stacked normalization and negative policy must agree because both
+		# contribute to the same axis range computation.
+		_validate_cross_overlay_stacking(p_xy_config, p_series_bindings, p_result)
+		if p_result.has_errors():
+			return false
+
 		# -- Warnings (never stop validation) --
 		_collect_warnings(p_xy_config, p_result)
 
@@ -299,6 +307,82 @@ class XYPlotValidator extends RefCounted:
 			LineValidator.validate(p_dataset, p_xy_config, pane_index, line_overlay_bindings, p_result)
 
 
+	####################################################################################################
+	# Cross-overlay stacking constraints
+	####################################################################################################
+
+	## Two stacked overlays sharing the same Y axis in the same pane both feed
+	## the axis range computation. They must therefore agree on
+	## [code]stacked_normalization[/code] (the pinned range vs data-derived
+	## range cannot coexist) and on [code]stacked_negative_policy[/code] (the
+	## range computation depends on a single coherent policy).
+	static func _validate_cross_overlay_stacking(p_xy_config: TauXYConfig, p_series_bindings: Array[TauXYSeriesBinding], p_result: ValidationResult) -> void:
+		# For each pane, resolve the y axis used by each stacked overlay.
+		# Only stacked overlays whose bindings are non-empty are considered:
+		# without bindings there is no axis to clash on.
+		var stacked_axis_by_pane_bar: Dictionary[int, AxisId] = {}
+		var stacked_axis_by_pane_line: Dictionary[int, AxisId] = {}
+
+		for binding in p_series_bindings:
+			match binding.overlay_type:
+				TauXYSeriesBinding.PaneOverlayType.BAR:
+					if not stacked_axis_by_pane_bar.has(binding.pane_index):
+						var bar_cfg := _get_stacked_bar_config(p_xy_config, binding.pane_index)
+						if bar_cfg != null:
+							stacked_axis_by_pane_bar[binding.pane_index] = binding.y_axis_id
+				TauXYSeriesBinding.PaneOverlayType.LINE:
+					if not stacked_axis_by_pane_line.has(binding.pane_index):
+						var line_cfg := _get_stacked_line_config(p_xy_config, binding.pane_index)
+						if line_cfg != null:
+							stacked_axis_by_pane_line[binding.pane_index] = binding.y_axis_id
+
+		# A clash exists when both a bar and a line stacked overlay land on the
+		# same axis in the same pane. The renderer-specific phase has already
+		# enforced "all stacked series of one overlay share a single axis", so
+		# the axis recorded above is unambiguous for each (pane, overlay) pair.
+		for pane_index in stacked_axis_by_pane_bar:
+			if not stacked_axis_by_pane_line.has(pane_index):
+				continue
+			var bar_axis: AxisId = stacked_axis_by_pane_bar[pane_index]
+			var line_axis: AxisId = stacked_axis_by_pane_line[pane_index]
+			if bar_axis != line_axis:
+				continue
+
+			var pane_cfg: TauPaneConfig = p_xy_config.panes[pane_index]
+			var bar_cfg := pane_cfg.get_overlay_config(TauXYSeriesBinding.PaneOverlayType.BAR) as TauBarConfig
+			var line_cfg := pane_cfg.get_overlay_config(TauXYSeriesBinding.PaneOverlayType.LINE) as TauLineConfig
+
+			if bar_cfg.stacked_normalization != line_cfg.stacked_normalization:
+				p_result.add_error("XYPlotValidator: pane %d, axis %s: stacked BAR and stacked LINE declare different stacked_normalization (BAR=%d, LINE=%d)" % [pane_index, Axis.as_string(bar_axis), int(bar_cfg.stacked_normalization), int(line_cfg.stacked_normalization)])
+
+			if bar_cfg.stacked_negative_policy != line_cfg.stacked_negative_policy:
+				p_result.add_error("XYPlotValidator: pane %d, axis %s: stacked BAR and stacked LINE declare different stacked_negative_policy (BAR=%d, LINE=%d)" % [pane_index, Axis.as_string(bar_axis), int(bar_cfg.stacked_negative_policy), int(line_cfg.stacked_negative_policy)])
+
+
+	## Returns the bar overlay config for the pane if it is in STACKED mode,
+	## null otherwise.
+	static func _get_stacked_bar_config(p_xy_config: TauXYConfig, p_pane_index: int) -> TauBarConfig:
+		var pane_cfg: TauPaneConfig = p_xy_config.panes[p_pane_index]
+		var bar_cfg := pane_cfg.get_overlay_config(TauXYSeriesBinding.PaneOverlayType.BAR) as TauBarConfig
+		if bar_cfg == null:
+			return null
+		if bar_cfg.mode != TauBarConfig.BarMode.STACKED:
+			return null
+		return bar_cfg
+
+
+	## Returns the line overlay config for the pane if it is in STACKED mode,
+	## null otherwise.
+	static func _get_stacked_line_config(p_xy_config: TauXYConfig, p_pane_index: int) -> TauLineConfig:
+		var pane_cfg: TauPaneConfig = p_xy_config.panes[p_pane_index]
+		var line_cfg := pane_cfg.get_overlay_config(TauXYSeriesBinding.PaneOverlayType.LINE) as TauLineConfig
+		if line_cfg == null:
+			return null
+		if line_cfg.mode != TauLineConfig.LineMode.STACKED:
+			return null
+		return line_cfg
+
+
 	####################################################################################################
 	# Warnings
 	####################################################################################################

From a255422d5f50e13e1532aa26ef54ea8e99e03554 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Fri, 8 May 2026 12:40:02 +0200
Subject: [PATCH 21/23] Add tests for STACKED bars

---
 .../test_bar_stacked_negative_fraction.gd}    | 152 ++---------
 .../test_bar_stacked_negative_fraction.gd.uid |   1 +
 .../test_bar_stacked_negative_fraction.tscn}  |  32 ++-
 .../stacked/test_bar_stacked_negative_none.gd | 253 ++++++++++++++++++
 .../test_bar_stacked_negative_none.gd.uid     |   1 +
 .../test_bar_stacked_negative_none.tscn       |  83 ++++++
 .../test_bar_stacked_negative_percent.gd      | 253 ++++++++++++++++++
 .../test_bar_stacked_negative_percent.gd.uid  |   1 +
 .../test_bar_stacked_negative_percent.tscn    |  83 ++++++
 .../test_bar_stacking_order.gd                |   0
 .../test_bar_stacking_order.gd.uid            |   0
 .../test_bar_stacking_order.tscn              |   2 +-
 .../test_bar_stacked_normalization.gd.uid     |   1 -
 13 files changed, 719 insertions(+), 143 deletions(-)
 rename addons/tau-plot/tests/bar/{stacked_normalization/test_bar_stacked_normalization.gd => stacked/test_bar_stacked_negative_fraction.gd} (60%)
 create mode 100644 addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.gd.uid
 rename addons/tau-plot/tests/bar/{stacked_normalization/test_bar_stacked_normalization.tscn => stacked/test_bar_stacked_negative_fraction.tscn} (69%)
 create mode 100644 addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd
 create mode 100644 addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd.uid
 create mode 100644 addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.tscn
 create mode 100644 addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.gd
 create mode 100644 addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.gd.uid
 create mode 100644 addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.tscn
 rename addons/tau-plot/tests/bar/{stacking_order => stacked}/test_bar_stacking_order.gd (100%)
 rename addons/tau-plot/tests/bar/{stacking_order => stacked}/test_bar_stacking_order.gd.uid (100%)
 rename addons/tau-plot/tests/bar/{stacking_order => stacked}/test_bar_stacking_order.tscn (97%)
 delete mode 100644 addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.gd.uid

diff --git a/addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.gd b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.gd
similarity index 60%
rename from addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.gd
rename to addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.gd
index 784fd8b..1a1bcdd 100644
--- a/addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.gd
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.gd
@@ -16,14 +16,14 @@ func _ready() -> void:
 
 func _setup_test_1() -> void:
 	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
-	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
-	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
-	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
-	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
 
 	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
 
-	%TestPlot1.title = "[CONTINUOUS] with stacked_normalization = NONE"
+	%TestPlot1.title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
 
 	var x_axis := TauAxisConfig.new()
 	x_axis.type = TauAxisConfig.Type.CONTINUOUS
@@ -38,7 +38,8 @@ func _setup_test_1() -> void:
 
 	var bar_config := TauBarConfig.new()
 	bar_config.mode = TauBarConfig.BarMode.STACKED
-	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.NONE
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.FRACTION
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.SKIP_NEGATIVES
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -74,14 +75,14 @@ func _setup_test_1() -> void:
 
 func _setup_test_2() -> void:
 	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
-	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
-	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
-	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
-	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
 
 	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
 
-	%TestPlot2.title = "[CONTINUOUS] with stacked_normalization = FRACTION"
+	%TestPlot2.title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
 
 	var x_axis := TauAxisConfig.new()
 	x_axis.type = TauAxisConfig.Type.CONTINUOUS
@@ -97,6 +98,7 @@ func _setup_test_2() -> void:
 	var bar_config := TauBarConfig.new()
 	bar_config.mode = TauBarConfig.BarMode.STACKED
 	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.FRACTION
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.DIVERGING
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -131,59 +133,7 @@ func _setup_test_2() -> void:
 ####################################################################################################
 
 func _setup_test_3() -> void:
-	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
-	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
-	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
-	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
-	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
-
-	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
-
-	%TestPlot3.title = "[CONTINUOUS] with stacked_normalization = PERCENT"
-
-	var x_axis := TauAxisConfig.new()
-	x_axis.type = TauAxisConfig.Type.CONTINUOUS
-	x_axis.scale = TauAxisConfig.Scale.LINEAR
-	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
-	x_axis.domain_padding_min = 0.5
-	x_axis.domain_padding_max = 0.5
-
-	var y_axis := TauAxisConfig.new()
-	y_axis.type = TauAxisConfig.Type.CONTINUOUS
-	y_axis.scale = TauAxisConfig.Scale.LINEAR
-	y_axis.format_tick_label = func(label: String) -> String:
-		return label + "%"
-
-	var bar_config := TauBarConfig.new()
-	bar_config.mode = TauBarConfig.BarMode.STACKED
-	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.PERCENT
-
-	var pane := TauPaneConfig.new()
-	pane.y_left_axis = y_axis
-	pane.overlays = [bar_config]
-
-	var config := TauXYConfig.new()
-	config.x_axis = x_axis
-	config.panes = [pane]
-
-	var sb_a := TauXYSeriesBinding.new()
-	sb_a.series_id = dataset.get_series_id_by_index(0)
-	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
-	sb_a.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_b := TauXYSeriesBinding.new()
-	sb_b.series_id = dataset.get_series_id_by_index(1)
-	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
-	sb_b.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_c := TauXYSeriesBinding.new()
-	sb_c.series_id = dataset.get_series_id_by_index(2)
-	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
-	sb_c.y_axis_id = TauPlot.AxisId.LEFT
-
-	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
-
-	%TestPlot3.plot_xy(dataset, config, bindings)
+	pass
 
 ####################################################################################################
 # Test 4
@@ -191,14 +141,14 @@ func _setup_test_3() -> void:
 
 func _setup_test_4() -> void:
 	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
-	var x := PackedStringArray(["One", "Two", "Three", "Four"])
-	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
-	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
-	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
 
 	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
 
-	%TestPlot4.title = "[CATEGORICAL] with stacked_normalization = NONE"
+	%TestPlot4.title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
 
 	var x_axis := TauAxisConfig.new()
 	x_axis.type = TauAxisConfig.Type.CATEGORICAL
@@ -209,7 +159,8 @@ func _setup_test_4() -> void:
 
 	var bar_config := TauBarConfig.new()
 	bar_config.mode = TauBarConfig.BarMode.STACKED
-	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.NONE
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.FRACTION
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.SKIP_NEGATIVES
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -245,14 +196,14 @@ func _setup_test_4() -> void:
 
 func _setup_test_5() -> void:
 	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
-	var x := PackedStringArray(["One", "Two", "Three", "Four"])
-	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
-	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
-	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
 
 	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
 
-	%TestPlot5.title = "[CATEGORICAL] with stacked_normalization = FRACTION"
+	%TestPlot5.title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
 
 	var x_axis := TauAxisConfig.new()
 	x_axis.type = TauAxisConfig.Type.CATEGORICAL
@@ -264,6 +215,7 @@ func _setup_test_5() -> void:
 	var bar_config := TauBarConfig.new()
 	bar_config.mode = TauBarConfig.BarMode.STACKED
 	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.FRACTION
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.DIVERGING
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -298,52 +250,4 @@ func _setup_test_5() -> void:
 ####################################################################################################
 
 func _setup_test_6() -> void:
-	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
-	var x := PackedStringArray(["One", "Two", "Three", "Four"])
-	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
-	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
-	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
-
-	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
-
-	%TestPlot6.title = "[CATEGORICAL] with stacked_normalization = PERCENT"
-
-	var x_axis := TauAxisConfig.new()
-	x_axis.type = TauAxisConfig.Type.CATEGORICAL
-
-	var y_axis := TauAxisConfig.new()
-	y_axis.type = TauAxisConfig.Type.CONTINUOUS
-	y_axis.scale = TauAxisConfig.Scale.LINEAR
-	y_axis.format_tick_label = func(label: String) -> String:
-		return label + "%"
-
-	var bar_config := TauBarConfig.new()
-	bar_config.mode = TauBarConfig.BarMode.STACKED
-	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.PERCENT
-
-	var pane := TauPaneConfig.new()
-	pane.y_left_axis = y_axis
-	pane.overlays = [bar_config]
-
-	var config := TauXYConfig.new()
-	config.x_axis = x_axis
-	config.panes = [pane]
-
-	var sb_a := TauXYSeriesBinding.new()
-	sb_a.series_id = dataset.get_series_id_by_index(0)
-	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
-	sb_a.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_b := TauXYSeriesBinding.new()
-	sb_b.series_id = dataset.get_series_id_by_index(1)
-	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
-	sb_b.y_axis_id = TauPlot.AxisId.LEFT
-
-	var sb_c := TauXYSeriesBinding.new()
-	sb_c.series_id = dataset.get_series_id_by_index(2)
-	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
-	sb_c.y_axis_id = TauPlot.AxisId.LEFT
-
-	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
-
-	%TestPlot6.plot_xy(dataset, config, bindings)
+	pass
diff --git a/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.gd.uid b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.gd.uid
new file mode 100644
index 0000000..8491167
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.gd.uid
@@ -0,0 +1 @@
+uid://cupqyf70ivodk
diff --git a/addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.tscn b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.tscn
similarity index 69%
rename from addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.tscn
rename to addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.tscn
index d2167ff..fec74e1 100644
--- a/addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.tscn
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.tscn
@@ -1,7 +1,7 @@
-[gd_scene load_steps=3 format=3 uid="uid://b3ryyw2r4icth"]
+[gd_scene load_steps=3 format=3 uid="uid://c4vb1a5ah2gsq"]
 
-[ext_resource type="Script" uid="uid://bvr1lhw6xrucv" path="res://addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.gd" id="1_13osl"]
-[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_t5ugu"]
+[ext_resource type="Script" uid="uid://cupqyf70ivodk" path="res://addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_fraction.gd" id="1_ak25b"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_x74kx"]
 
 [node name="Bars" type="VBoxContainer"]
 anchors_preset = 15
@@ -9,12 +9,12 @@ anchor_right = 1.0
 anchor_bottom = 1.0
 grow_horizontal = 2
 grow_vertical = 2
-script = ExtResource("1_13osl")
+script = ExtResource("1_ak25b")
 
 [node name="Title" type="Label" parent="."]
 layout_mode = 2
 theme_override_font_sizes/font_size = 32
-text = "Test stacked bars normalization"
+text = "Test stacked bars negative policy with normalization = FRACTION"
 horizontal_alignment = 1
 
 [node name="GridContainer" type="GridContainer" parent="."]
@@ -30,8 +30,8 @@ layout_mode = 2
 size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
-script = ExtResource("2_t5ugu")
-title = "[CONTINUOUS] with stacked_normalization = NONE"
+script = ExtResource("2_x74kx")
+title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
@@ -40,8 +40,8 @@ layout_mode = 2
 size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
-script = ExtResource("2_t5ugu")
-title = "[CONTINUOUS] with stacked_normalization = FRACTION"
+script = ExtResource("2_x74kx")
+title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
@@ -50,8 +50,7 @@ layout_mode = 2
 size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
-script = ExtResource("2_t5ugu")
-title = "[CONTINUOUS] with stacked_normalization = PERCENT"
+script = ExtResource("2_x74kx")
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
@@ -60,8 +59,8 @@ layout_mode = 2
 size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
-script = ExtResource("2_t5ugu")
-title = "[CATEGORICAL] with stacked_normalization = NONE"
+script = ExtResource("2_x74kx")
+title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
@@ -70,8 +69,8 @@ layout_mode = 2
 size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
-script = ExtResource("2_t5ugu")
-title = "[CATEGORICAL] with stacked_normalization = FRACTION"
+script = ExtResource("2_x74kx")
+title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
@@ -80,6 +79,5 @@ layout_mode = 2
 size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
-script = ExtResource("2_t5ugu")
-title = "[CATEGORICAL] with stacked_normalization = PERCENT"
+script = ExtResource("2_x74kx")
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd
new file mode 100644
index 0000000..6b6675e
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd
@@ -0,0 +1,253 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot1.title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.NONE
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.SKIP_NEGATIVES
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot2.title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.NONE
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	pass
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot4.title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.NONE
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.SKIP_NEGATIVES
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot4.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot5.title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.NONE
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot5.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	pass
diff --git a/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd.uid b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd.uid
new file mode 100644
index 0000000..5eb42a0
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd.uid
@@ -0,0 +1 @@
+uid://dwn5xtyqivtr
diff --git a/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.tscn b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.tscn
new file mode 100644
index 0000000..94ff99a
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.tscn
@@ -0,0 +1,83 @@
+[gd_scene load_steps=3 format=3 uid="uid://dlcfw43nxd2lh"]
+
+[ext_resource type="Script" uid="uid://dwn5xtyqivtr" path="res://addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd" id="1_543ko"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_xjs2v"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_543ko")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test stacked bars negative policy with normalization = NONE"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xjs2v")
+title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xjs2v")
+title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xjs2v")
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xjs2v")
+title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xjs2v")
+title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_xjs2v")
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.gd b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.gd
new file mode 100644
index 0000000..a8ab269
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.gd
@@ -0,0 +1,253 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot1.title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.PERCENT
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.SKIP_NEGATIVES
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot2.title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.PERCENT
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	pass
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot4.title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.PERCENT
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.SKIP_NEGATIVES
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot4.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([-5.0, -10.0, 15.0, -20.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, -30.0, -35.0, -40.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, -50.0, -60.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot5.title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var bar_config := TauBarConfig.new()
+	bar_config.mode = TauBarConfig.BarMode.STACKED
+	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.PERCENT
+	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [bar_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.BAR
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot5.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	pass
diff --git a/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.gd.uid b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.gd.uid
new file mode 100644
index 0000000..5569c29
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.gd.uid
@@ -0,0 +1 @@
+uid://54kryum6jpqn
diff --git a/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.tscn b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.tscn
new file mode 100644
index 0000000..883707b
--- /dev/null
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.tscn
@@ -0,0 +1,83 @@
+[gd_scene load_steps=3 format=3 uid="uid://15u65yn0mbjv"]
+
+[ext_resource type="Script" uid="uid://54kryum6jpqn" path="res://addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_percent.gd" id="1_ru6as"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_1qp56"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_ru6as")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test stacked bars negative policy with normalization = PERCENT"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_1qp56")
+title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_1qp56")
+title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_1qp56")
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_1qp56")
+title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_1qp56")
+title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_1qp56")
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd b/addons/tau-plot/tests/bar/stacked/test_bar_stacking_order.gd
similarity index 100%
rename from addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd
rename to addons/tau-plot/tests/bar/stacked/test_bar_stacking_order.gd
diff --git a/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd.uid b/addons/tau-plot/tests/bar/stacked/test_bar_stacking_order.gd.uid
similarity index 100%
rename from addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd.uid
rename to addons/tau-plot/tests/bar/stacked/test_bar_stacking_order.gd.uid
diff --git a/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.tscn b/addons/tau-plot/tests/bar/stacked/test_bar_stacking_order.tscn
similarity index 97%
rename from addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.tscn
rename to addons/tau-plot/tests/bar/stacked/test_bar_stacking_order.tscn
index f6539b7..679504f 100644
--- a/addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.tscn
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacking_order.tscn
@@ -1,6 +1,6 @@
 [gd_scene load_steps=3 format=3 uid="uid://dtphakr4ucelg"]
 
-[ext_resource type="Script" uid="uid://dc8xbkxehai5e" path="res://addons/tau-plot/tests/bar/stacking_order/test_bar_stacking_order.gd" id="1_6dmnp"]
+[ext_resource type="Script" uid="uid://dc8xbkxehai5e" path="res://addons/tau-plot/tests/bar/stacked/test_bar_stacking_order.gd" id="1_6dmnp"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_p3gyn"]
 
 [node name="Bars" type="VBoxContainer"]
diff --git a/addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.gd.uid b/addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.gd.uid
deleted file mode 100644
index 4518e76..0000000
--- a/addons/tau-plot/tests/bar/stacked_normalization/test_bar_stacked_normalization.gd.uid
+++ /dev/null
@@ -1 +0,0 @@
-uid://bvr1lhw6xrucv

From 02e3e16655b319f29c79769b6061efc4cae5a414 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Mon, 11 May 2026 23:33:47 +0200
Subject: [PATCH 22/23] Implement stacked lines

---
 addons/tau-plot/plot/xy/bar/bar_renderer.gd   | 151 ++------
 addons/tau-plot/plot/xy/line/line_renderer.gd | 103 +++--
 .../tau-plot/plot/xy/stacked_series_values.gd | 176 +++++++++
 .../plot/xy/stacked_series_values.gd.uid      |   1 +
 addons/tau-plot/plot/xy/xy_plot.gd            | 131 ++++---
 .../stacked/test_bar_stacked_negative_none.gd |   4 +
 .../test_line_stacked_negative_fraction.gd    | 351 +++++++++++++++++
 ...test_line_stacked_negative_fraction.gd.uid |   1 +
 .../test_line_stacked_negative_fraction.tscn  |  85 +++++
 .../test_line_stacked_negative_none.gd        | 358 ++++++++++++++++++
 .../test_line_stacked_negative_none.gd.uid    |   1 +
 .../test_line_stacked_negative_none.tscn      |  85 +++++
 .../test_line_stacked_negative_percent.gd     | 351 +++++++++++++++++
 .../test_line_stacked_negative_percent.gd.uid |   1 +
 .../test_line_stacked_negative_percent.tscn   |  83 ++++
 .../line/stacked/test_line_stacking_order.gd  | 349 +++++++++++++++++
 .../stacked/test_line_stacking_order.gd.uid   |   1 +
 .../stacked/test_line_stacking_order.tscn     |  85 +++++
 18 files changed, 2118 insertions(+), 199 deletions(-)
 create mode 100644 addons/tau-plot/plot/xy/stacked_series_values.gd
 create mode 100644 addons/tau-plot/plot/xy/stacked_series_values.gd.uid
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd.uid
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.tscn
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd.uid
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.tscn
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd.uid
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.tscn
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd.uid
 create mode 100644 addons/tau-plot/tests/line/stacked/test_line_stacking_order.tscn

diff --git a/addons/tau-plot/plot/xy/bar/bar_renderer.gd b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
index ac0cd50..bda77b0 100644
--- a/addons/tau-plot/plot/xy/bar/bar_renderer.gd
+++ b/addons/tau-plot/plot/xy/bar/bar_renderer.gd
@@ -8,6 +8,7 @@ const Axis = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").Axis
 const VisualAttributes = preload("res://addons/tau-plot/plot/xy/visual_attributes.gd").VisualAttributes
 const BarVisualAttributes := preload("res://addons/tau-plot/plot/xy/bar/bar_visual_attributes.gd").BarVisualAttributes
 const BarHitRecord := preload("res://addons/tau-plot/plot/xy/bar/bar_hit_record.gd").BarHitRecord
+const StackedSeriesValues := preload("res://addons/tau-plot/plot/xy/stacked_series_values.gd").StackedSeriesValues
 
 
 # Draws bar overlays from a XYLayout + Dataset.
@@ -662,74 +663,14 @@ class BarRenderer extends Control:
 				_draw_bar(p_pane_rect, center_px, zero_px, y_px, bar_width_px, color, series_index, i, x_value, y_value, y_value)
 
 
-	# Builds one X column's worth of stacked bar segments in dataset order,
-	# applying the active normalization and negative policy. The returned list
-	# drives the second-pass painter, which looks up segments by series_index.
-	func _compute_stacked_segments_at(p_series_count: int, p_sample_index: int) -> Array:
-		var normalization := _bar_config.stacked_normalization
-		var policy := _bar_config.stacked_negative_policy
-
-		# DIVERGING needs positive and absolute-negative totals tracked
-		# separately so each half-stack normalizes against its own total.
-		var pos_total := 0.0
-		var neg_total_abs := 0.0
-		if normalization != TauBarConfig.StackedNormalization.NONE:
-			for series_index in range(p_series_count):
-				var series_id := _get_bar_series_id(series_index)
-				var y_value := _dataset.get_series_y(series_id, p_sample_index)
-				if is_nan(y_value) or is_inf(y_value):
-					continue
-				if y_value >= 0.0:
-					pos_total += y_value
-				else:
-					neg_total_abs += -y_value
-
-		var pos_scale := 1.0
-		var neg_scale := 1.0
-		match normalization:
-			TauBarConfig.StackedNormalization.FRACTION:
-				pos_scale = 1.0 / pos_total if pos_total > 0.0 else 0.0
-				neg_scale = 1.0 / neg_total_abs if neg_total_abs > 0.0 else 0.0
-
-			TauBarConfig.StackedNormalization.PERCENT:
-				pos_scale = 100.0 / pos_total if pos_total > 0.0 else 0.0
-				neg_scale = 100.0 / neg_total_abs if neg_total_abs > 0.0 else 0.0
-
-		var segments: Array = []
-		var accum_pos := 0.0
-		var accum_neg := 0.0
-
-		for series_index in range(p_series_count):
-			var series_id := _get_bar_series_id(series_index)
-			var y_raw := _dataset.get_series_y(series_id, p_sample_index)
-			if is_nan(y_raw) or is_inf(y_raw):
-				continue
-
-			match policy:
-				TauBarConfig.StackedNegativePolicy.SKIP_NEGATIVES:
-					if y_raw < 0.0:
-						continue
-					var y := y_raw * pos_scale
-					var y0 := accum_pos
-					var y1 := accum_pos + y
-					segments.append({"series_index": series_index, "y0": y0, "y1": y1})
-					accum_pos = y1
-
-				TauBarConfig.StackedNegativePolicy.DIVERGING:
-					if y_raw >= 0.0:
-						var y := y_raw * pos_scale
-						var y0 := accum_pos
-						var y1 := accum_pos + y
-						segments.append({"series_index": series_index, "y0": y0, "y1": y1})
-						accum_pos = y1
-					else:
-						var y := y_raw * neg_scale
-						var y0 := accum_neg
-						var y1 := accum_neg + y
-						segments.append({"series_index": series_index, "y0": y0, "y1": y1})
-						accum_neg = y1
-
-		return segments
+	# Builds the cumulative stacked values for every (series, sample) at once,
+	# delegating normalization and negative-policy handling to the shared
+	# helper. The two stacked painters look up y_plotted/y_baseline by
+	# (series_local, sample_index) instead of carrying their own pass.
+	func _compute_stacked_values() -> StackedSeriesValues:
+		return StackedSeriesValues.new(_dataset, _bar_series_ids,
+				_bar_config.stacked_normalization,
+				_bar_config.stacked_negative_policy)
 
 
 	func _draw_stacked_bars(p_pane_rect: Rect2, p_series_count: int) -> void:
@@ -759,41 +700,27 @@ class BarRenderer extends Control:
 		var bar_width_px := _geometry_cache.compute_categorical_bar_width_px(p_pane_rect, n)
 		bar_width_px = max(bar_width_px, _MIN_BAR_WIDTH_PX)
 
-		# First pass: compute all segments for all categories (in dataset order for stacking)
-		var all_segments: Array = []  # Array of arrays, one per category. FIXME Godot 4.5 does not support nested typed collections.
-		all_segments.resize(n)
-		for category_index in range(n):
-			all_segments[category_index] = _compute_stacked_segments_at(p_series_count, category_index)
+		var stacked_values := _compute_stacked_values()
 
-		# Second pass: paint in z_order (series first, then categories)
 		var draw_order := _get_series_draw_order(p_series_count)
 		for series_index: int in draw_order:
 			for category_index in range(n):
-				var group_center_px := _layout.map_x_category_center_to_px(_pane_index, category_index)
-				var segments = all_segments[category_index]
-
-				# Find the segment for this series at this category
-				var segment = null
-				for seg in segments:
-					if seg["series_index"] == series_index:
-						segment = seg
-						break
-
-				if segment == null:
-					continue  # This series had no valid data at this category
+				var y_plotted: float = stacked_values.get_y_plotted(series_index, category_index)
+				if is_nan(y_plotted):
+					continue
 
-				var y0_px := _layout.map_y_to_px(_pane_index, segment["y0"], stacked_axis_id)
-				var y1_px := _layout.map_y_to_px(_pane_index, segment["y1"], stacked_axis_id)
+				var group_center_px := _layout.map_x_category_center_to_px(_pane_index, category_index)
+				var y0_px := _layout.map_y_to_px(_pane_index, stacked_values.get_y_baseline(series_index, category_index), stacked_axis_id)
+				var y1_px := _layout.map_y_to_px(_pane_index, y_plotted, stacked_axis_id)
 
 				var x_value: Variant = categories[category_index]
-				var y_value: float = segment["y1"]
 				# Callbacks see the raw dataset value, not the stacked top.
-				var y_raw: float = _dataset.get_series_y(_get_bar_series_id(series_index), category_index)
+				var y_raw: float = stacked_values.get_y_raw(series_index, category_index)
 				var base_color := _get_bar_color(series_index, category_index, x_value, y_raw)
 				var alpha_override := _get_bar_alpha(series_index, category_index, x_value, y_raw)
 				var color := _apply_alpha_override(base_color, alpha_override)
 
-				_draw_bar(p_pane_rect, group_center_px, y0_px, y1_px, bar_width_px, color, series_index, category_index, x_value, y_value, y_raw)
+				_draw_bar(p_pane_rect, group_center_px, y0_px, y1_px, bar_width_px, color, series_index, category_index, x_value, y_plotted, y_raw)
 
 
 	# FIXME: the second pass here duplicates _draw_stacked_bars_categorical almost line-for-line.
@@ -805,42 +732,21 @@ class BarRenderer extends Control:
 
 		var resolved_bar_width_policy := _geometry_cache.get_resolved_bar_width_policy()
 
-		# First pass: compute all segments for all X positions (in dataset order for stacking)
-		var all_segments: Array = []  # Array of arrays, one per X position. FIXME Godot 4.5 does not support nested typed collections.
-		all_segments.resize(n)
-		for i in range(n):
-			var x_value := float(_dataset.get_shared_x(i))
-			if is_nan(x_value) or is_inf(x_value):
-				all_segments[i] = []
-				continue
-			if not _is_x_value_valid_for_scale(x_value):
-				all_segments[i] = []
-				continue
-
-			all_segments[i] = _compute_stacked_segments_at(p_series_count, i)
-
-		# Second pass: paint in z_order (series first, then X positions)
+		var stacked_values := _compute_stacked_values()
+
 		var draw_order := _get_series_draw_order(p_series_count)
 		for series_index: int in draw_order:
 			for i in range(n):
+				var y_plotted: float = stacked_values.get_y_plotted(series_index, i)
+				if is_nan(y_plotted):
+					continue
+
 				var x_value := float(_dataset.get_shared_x(i))
 				if is_nan(x_value) or is_inf(x_value):
 					continue
 				if not _is_x_value_valid_for_scale(x_value):
 					continue
 
-				var segments = all_segments[i]
-
-				# Find the segment for this series at this X position
-				var segment = null
-				for seg in segments:
-					if seg["series_index"] == series_index:
-						segment = seg
-						break
-
-				if segment == null:
-					continue  # This series had no valid data at this X position
-
 				var group_center_px := _layout.map_x_to_px(_pane_index, x_value)
 
 				var bar_width_px := 0.0
@@ -852,17 +758,16 @@ class BarRenderer extends Control:
 						push_error("BarRenderer: bar_width_policy %d is not supported for STACKED + CONTINUOUS" % int(resolved_bar_width_policy))
 						return
 
-				var y0_px := _layout.map_y_to_px(_pane_index, segment["y0"], stacked_axis_id)
-				var y1_px := _layout.map_y_to_px(_pane_index, segment["y1"], stacked_axis_id)
+				var y0_px := _layout.map_y_to_px(_pane_index, stacked_values.get_y_baseline(series_index, i), stacked_axis_id)
+				var y1_px := _layout.map_y_to_px(_pane_index, y_plotted, stacked_axis_id)
 
-				var y_value: float = segment["y1"]
 				# Callbacks see the raw dataset value, not the stacked top.
-				var y_raw: float = _dataset.get_series_y(_get_bar_series_id(series_index), i)
+				var y_raw: float = stacked_values.get_y_raw(series_index, i)
 				var base_color := _get_bar_color(series_index, i, x_value, y_raw)
 				var alpha_override := _get_bar_alpha(series_index, i, x_value, y_raw)
 				var color := _apply_alpha_override(base_color, alpha_override)
 
-				_draw_bar(p_pane_rect, group_center_px, y0_px, y1_px, bar_width_px, color, series_index, i, x_value, y_value, y_raw)
+				_draw_bar(p_pane_rect, group_center_px, y0_px, y1_px, bar_width_px, color, series_index, i, x_value, y_plotted, y_raw)
 
 
 	func _draw_independent_bars(p_pane_rect: Rect2, p_series_count: int) -> void:
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index c595cf1..1c324d3 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -7,6 +7,7 @@ const Axis = preload("res://addons/tau-plot/plot/xy/xy_axes.gd").Axis
 const VisualAttributes = preload("res://addons/tau-plot/plot/xy/visual_attributes.gd").VisualAttributes
 const LineVisualAttributes := preload("res://addons/tau-plot/plot/xy/line/line_visual_attributes.gd").LineVisualAttributes
 const LineHitRecord := preload("res://addons/tau-plot/plot/xy/line/line_hit_record.gd").LineHitRecord
+const StackedSeriesValues := preload("res://addons/tau-plot/plot/xy/stacked_series_values.gd").StackedSeriesValues
 
 
 # Draws line overlays from an XYLayout + Dataset.
@@ -77,6 +78,14 @@ const LineHitRecord := preload("res://addons/tau-plot/plot/xy/line/line_hit_reco
 #   are colored consistently with the underlying segment endpoints so the
 #   resulting interpolation matches the chosen interpolation mode.
 #
+# STACKED mode:
+# - Each polyline is drawn at the per-X cumulative top of its layer.
+#   Layer 0 sits at the bottom, ordered by dataset index.
+# - Color and alpha callbacks always receive the original dataset value,
+#   never the cumulative or the normalized value.
+# - LineHitRecord.y_plotted_value carries the cumulative top.
+#   LineHitRecord.y_raw_value carries the original dataset value.
+#
 # LineValidator is expected to enforce binding-level typing constraints.
 class LineRenderer extends Control:
 	# Number of sub-segments inserted between two consecutive samples by
@@ -210,30 +219,35 @@ class LineRenderer extends Control:
 		if series_count <= 0:
 			return
 
-		var draw_order := _get_series_draw_order(series_count)
+		var stacked_values: StackedSeriesValues = null
+		if _line_config.mode == TauLineConfig.LineMode.STACKED:
+			stacked_values = StackedSeriesValues.new(_dataset, _line_series_ids,
+					_line_config.stacked_normalization,
+					_line_config.stacked_negative_policy)
 
+		var draw_order := _get_series_draw_order(series_count)
 		for draw_rank in range(draw_order.size()):
 			var series_index: int = draw_order[draw_rank]
-			_draw_series_independent(series_index)
+			_draw_series(series_index, stacked_values)
 
 
-	# Draws a single series as one or more polyline runs, respecting the
-	# active gap policy. Run emission follows these rules:
+	# Run emission rules, applied by both variants:
 	#   - A valid sample is appended to the current run.
-	#   - An invalid sample (NaN/Inf X or Y, or a value forbidden by the
-	#     active axis scale) is handled according to gap_policy:
+	#   - An invalid sample (NaN/Inf X or Y, value forbidden by the active
+	#     axis scale, or dropped by the negative policy in STACKED mode)
+	#     is handled according to gap_policy:
 	#     - SKIP   flushes the current run and starts a new one.
 	#     - BRIDGE drops the sample and keeps appending into the same run.
-	#   - A run of fewer than two points is discarded (no polyline).
-	func _draw_series_independent(p_series_index: int) -> void:
+	#   - A run of fewer than two points is discarded.
+	func _draw_series(p_series_index: int, p_stacked: StackedSeriesValues) -> void:
 		var x_cfg := _get_x_axis_config()
 		if x_cfg != null and x_cfg.type == TauAxisConfig.Type.CATEGORICAL:
-			_draw_series_categorical(p_series_index)
+			_draw_series_categorical(p_series_index, p_stacked)
 		else:
-			_draw_series_continuous(p_series_index)
+			_draw_series_continuous(p_series_index, p_stacked)
 
 
-	func _draw_series_continuous(p_series_index: int) -> void:
+	func _draw_series_continuous(p_series_index: int, p_stacked: StackedSeriesValues) -> void:
 		var series_id := _get_line_series_id(p_series_index)
 		var global_series_index := _get_global_series_index(p_series_index)
 		var width_px: float = _line_style.get_series_width_px(global_series_index)
@@ -245,6 +259,10 @@ class LineRenderer extends Control:
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
 
+		var independent_y: PackedFloat64Array
+		if p_stacked == null:
+			independent_y = _build_independent_y_row(series_id)
+
 		var run := PackedVector2Array()
 		var run_colors := PackedColorArray()
 		# Parallel arrays describing the real samples appended to the current
@@ -269,8 +287,16 @@ class LineRenderer extends Control:
 					real_dataset_indices = PackedInt32Array()
 				continue
 
-			var y_value := _dataset.get_series_y(series_id, i)
-			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
+			var y_plotted: float
+			var y_raw: float
+			if p_stacked != null:
+				y_plotted = p_stacked.get_y_plotted(p_series_index, i)
+				y_raw = p_stacked.get_y_raw(p_series_index, i)
+			else:
+				y_plotted = independent_y[i]
+				y_raw = y_plotted
+
+			if is_nan(y_plotted):
 				if not bridge:
 					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
 					run = PackedVector2Array()
@@ -280,9 +306,9 @@ class LineRenderer extends Control:
 				continue
 
 			var x_px := _layout.map_x_to_px(_pane_index, x_value)
-			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
+			var y_px := _layout.map_y_to_px(_pane_index, y_plotted, y_axis_id)
 			var screen_pos := _layout.map_point_to_screen(x_px, y_px)
-			var sample_color := _resolve_sample_color(p_series_index, i, x_value, y_value)
+			var sample_color := _resolve_sample_color(p_series_index, i, x_value, y_raw)
 			_append_with_interpolation(run, run_colors, screen_pos, sample_color, interpolation)
 			# The real sample is always the last vertex appended by
 			# _append_with_interpolation, regardless of the interpolation mode.
@@ -293,15 +319,15 @@ class LineRenderer extends Control:
 			record.series_id = series_id
 			record.sample_index = i
 			record.x_value = x_value
-			record.y_plotted_value = y_value
-			record.y_raw_value = y_value
+			record.y_plotted_value = y_plotted
+			record.y_raw_value = y_raw
 			record.screen_position = screen_pos
 			_hit_records.append(record)
 
 		_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
 
 
-	func _draw_series_categorical(p_series_index: int) -> void:
+	func _draw_series_categorical(p_series_index: int, p_stacked: StackedSeriesValues) -> void:
 		var series_id := _get_line_series_id(p_series_index)
 		var global_series_index := _get_global_series_index(p_series_index)
 		var width_px: float = _line_style.get_series_width_px(global_series_index)
@@ -313,6 +339,10 @@ class LineRenderer extends Control:
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
 
+		var independent_y: PackedFloat64Array
+		if p_stacked == null:
+			independent_y = _build_independent_y_row(series_id)
+
 		var categories := _layout.domain.x_categories
 		var run := PackedVector2Array()
 		var run_colors := PackedColorArray()
@@ -321,8 +351,16 @@ class LineRenderer extends Control:
 		var sample_count := _dataset.get_series_sample_count(series_id)
 
 		for cat_idx in range(sample_count):
-			var y_value := _dataset.get_series_y(series_id, cat_idx)
-			if is_nan(y_value) or is_inf(y_value) or not _is_y_value_valid_for_scale(series_id, y_value):
+			var y_plotted: float
+			var y_raw: float
+			if p_stacked != null:
+				y_plotted = p_stacked.get_y_plotted(p_series_index, cat_idx)
+				y_raw = p_stacked.get_y_raw(p_series_index, cat_idx)
+			else:
+				y_plotted = independent_y[cat_idx]
+				y_raw = y_plotted
+
+			if is_nan(y_plotted):
 				if not bridge:
 					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
 					run = PackedVector2Array()
@@ -332,10 +370,10 @@ class LineRenderer extends Control:
 				continue
 
 			var x_px := _layout.map_x_category_center_to_px(_pane_index, cat_idx)
-			var y_px := _layout.map_y_to_px(_pane_index, y_value, y_axis_id)
+			var y_px := _layout.map_y_to_px(_pane_index, y_plotted, y_axis_id)
 			var screen_pos := _layout.map_point_to_screen(x_px, y_px)
 			var x_value: Variant = categories[cat_idx]
-			var sample_color := _resolve_sample_color(p_series_index, cat_idx, x_value, y_value)
+			var sample_color := _resolve_sample_color(p_series_index, cat_idx, x_value, y_raw)
 			_append_with_interpolation(run, run_colors, screen_pos, sample_color, interpolation)
 			real_polyline_indices.append(run.size() - 1)
 			real_dataset_indices.append(cat_idx)
@@ -344,14 +382,31 @@ class LineRenderer extends Control:
 			record.series_id = series_id
 			record.sample_index = cat_idx
 			record.x_value = x_value
-			record.y_plotted_value = y_value
-			record.y_raw_value = y_value
+			record.y_plotted_value = y_plotted
+			record.y_raw_value = y_raw
 			record.screen_position = screen_pos
 			_hit_records.append(record)
 
 		_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
 
 
+	# Marks dropped samples (NaN, Inf, log-axis violations) as NAN up front
+	# so the inner draw loop only needs a single is_nan() check per sample.
+	func _build_independent_y_row(p_series_id: int) -> PackedFloat64Array:
+		var sample_count := _dataset.get_series_sample_count(p_series_id)
+		var y_plotted := PackedFloat64Array()
+		y_plotted.resize(sample_count)
+		y_plotted.fill(NAN)
+		for i in range(sample_count):
+			var y := _dataset.get_series_y(p_series_id, i)
+			if is_nan(y) or is_inf(y):
+				continue
+			if not _is_y_value_valid_for_scale(p_series_id, y):
+				continue
+			y_plotted[i] = y
+		return y_plotted
+
+
 	# Each appended sample (real or synthetic) gets the new sample's color.
 	# Combined with linear interpolation by draw_polyline_colors() between
 	# consecutive vertices, this places the color transition at the segment
diff --git a/addons/tau-plot/plot/xy/stacked_series_values.gd b/addons/tau-plot/plot/xy/stacked_series_values.gd
new file mode 100644
index 0000000..aff6c4b
--- /dev/null
+++ b/addons/tau-plot/plot/xy/stacked_series_values.gd
@@ -0,0 +1,176 @@
+const Dataset := preload("res://addons/tau-plot/model/dataset.gd").Dataset
+const StackedNormalization = preload("res://addons/tau-plot/plot/xy/stacked_normalization.gd").StackedNormalization
+const StackedNegativePolicy = preload("res://addons/tau-plot/plot/xy/stacked_negative_policy.gd").StackedNegativePolicy
+
+
+## Per-(series, sample) cumulative values for a stacked overlay.
+##
+## Built from an ordered list of stacked series sharing a SHARED_X dataset.
+## Layer order matches the order of series_ids: layer 0 sits at the bottom.
+##
+## Values are read through [method get_y_plotted], [method get_y_baseline],
+## and [method get_y_raw], all keyed by (series_local, sample_index).
+## series_local matches the position of the corresponding series_id in the
+## list passed at construction. NAN means the sample is dropped (NaN/Inf
+## in the dataset, or removed by the active negative policy) and must be
+## ignored by the caller.
+class StackedSeriesValues extends RefCounted:
+
+	var _series_count: int = 0
+	var _sample_count: int = 0
+
+	# Flat layout sidesteps the copy-on-write of nested
+	# Array[PackedFloat64Array] element access in GDScript, where reading
+	# an element into a local yields a copy and breaks in-place mutation.
+	# Index = series_local * _sample_count + sample_index.
+	var _y_plotted: PackedFloat64Array = PackedFloat64Array()
+	var _y_baseline: PackedFloat64Array = PackedFloat64Array()
+	var _y_raw: PackedFloat64Array = PackedFloat64Array()
+
+
+	## p_series_ids must already be in stacking order (layer 0 first) and
+	## refer to series of the SHARED_X p_dataset.
+	func _init(p_dataset: Dataset, p_series_ids: PackedInt64Array,
+				p_normalization: StackedNormalization,
+				p_negative_policy: StackedNegativePolicy) -> void:
+		_series_count = p_series_ids.size()
+		_sample_count = p_dataset.get_shared_sample_count()
+
+		var cell_count := _series_count * _sample_count
+		_y_plotted.resize(cell_count)
+		_y_plotted.fill(NAN)
+		_y_baseline.resize(cell_count)
+		_y_baseline.fill(NAN)
+		_y_raw.resize(cell_count)
+		_y_raw.fill(NAN)
+
+		_fill_y_raw(p_dataset, p_series_ids)
+
+		for sample_index in range(_sample_count):
+			var pos_scale := 1.0
+			var neg_scale := 1.0
+			if p_normalization != StackedNormalization.NONE:
+				var totals := _per_x_totals(sample_index, p_negative_policy)
+				var pos_total: float = totals.x
+				var neg_total_abs: float = totals.y
+				match p_normalization:
+					StackedNormalization.FRACTION:
+						pos_scale = 1.0 / pos_total if pos_total > 0.0 else 0.0
+						neg_scale = 1.0 / neg_total_abs if neg_total_abs > 0.0 else 0.0
+					StackedNormalization.PERCENT:
+						pos_scale = 100.0 / pos_total if pos_total > 0.0 else 0.0
+						neg_scale = 100.0 / neg_total_abs if neg_total_abs > 0.0 else 0.0
+
+			match p_negative_policy:
+				StackedNegativePolicy.SKIP_NEGATIVES:
+					_accumulate_skip_negatives(sample_index, pos_scale)
+				StackedNegativePolicy.DIVERGING:
+					_accumulate_diverging(sample_index, pos_scale, neg_scale)
+				StackedNegativePolicy.SIGNED_SUM:
+					_accumulate_signed_sum(sample_index, pos_scale)
+
+
+	## Painted top of this (series, sample) in axis units.
+	func get_y_plotted(p_series_local: int, p_sample_index: int) -> float:
+		return _y_plotted[p_series_local * _sample_count + p_sample_index]
+
+
+	## Painted top of the layer below this (series, sample) in the same
+	## half-stack, or 0.0 for the bottom-most contribution at this X.
+	func get_y_baseline(p_series_local: int, p_sample_index: int) -> float:
+		return _y_baseline[p_series_local * _sample_count + p_sample_index]
+
+
+	## Original dataset value at this (series, sample), before stacking,
+	## normalization, or accumulation.
+	func get_y_raw(p_series_local: int, p_sample_index: int) -> float:
+		return _y_raw[p_series_local * _sample_count + p_sample_index]
+
+
+	####################################################################################################
+	# Private
+	####################################################################################################
+
+	# Negative-policy filtering belongs to the accumulation step, so this
+	# pass keeps every finite raw value regardless of sign.
+	func _fill_y_raw(p_dataset: Dataset, p_series_ids: PackedInt64Array) -> void:
+		for series_local in range(_series_count):
+			var series_id := p_series_ids[series_local]
+			var row_offset := series_local * _sample_count
+			for sample_index in range(_sample_count):
+				var v := p_dataset.get_series_y(series_id, sample_index)
+				if is_nan(v) or is_inf(v):
+					continue
+				_y_raw[row_offset + sample_index] = v
+
+
+	# DIVERGING is the only policy that needs the absolute negative total.
+	# The other policies leave it at zero.
+	func _per_x_totals(p_sample_index: int, p_policy: StackedNegativePolicy) -> Vector2:
+		var pos_total := 0.0
+		var neg_total_abs := 0.0
+		for series_local in range(_series_count):
+			var v: float = _y_raw[series_local * _sample_count + p_sample_index]
+			if is_nan(v):
+				continue
+			match p_policy:
+				StackedNegativePolicy.SKIP_NEGATIVES:
+					if v >= 0.0:
+						pos_total += v
+				StackedNegativePolicy.DIVERGING:
+					if v >= 0.0:
+						pos_total += v
+					else:
+						neg_total_abs += -v
+				StackedNegativePolicy.SIGNED_SUM:
+					pos_total += v
+		return Vector2(pos_total, neg_total_abs)
+
+
+	func _accumulate_skip_negatives(p_sample_index: int, p_pos_scale: float) -> void:
+		var accum_pos := 0.0
+		for series_local in range(_series_count):
+			var idx := series_local * _sample_count + p_sample_index
+			var v: float = _y_raw[idx]
+			if is_nan(v) or v < 0.0:
+				continue
+			var scaled := v * p_pos_scale
+			_y_baseline[idx] = accum_pos
+			accum_pos += scaled
+			_y_plotted[idx] = accum_pos
+
+
+	func _accumulate_diverging(p_sample_index: int, p_pos_scale: float, p_neg_scale: float) -> void:
+		var accum_pos := 0.0
+		var accum_neg := 0.0
+		for series_local in range(_series_count):
+			var idx := series_local * _sample_count + p_sample_index
+			var v: float = _y_raw[idx]
+			if is_nan(v):
+				continue
+			if v >= 0.0:
+				var scaled := v * p_pos_scale
+				_y_baseline[idx] = accum_pos
+				accum_pos += scaled
+				_y_plotted[idx] = accum_pos
+			else:
+				var scaled := v * p_neg_scale
+				_y_baseline[idx] = accum_neg
+				accum_neg += scaled
+				_y_plotted[idx] = accum_neg
+
+
+	# A negative contribution dips the cumulative below the previous layer,
+	# producing the streamgraph pattern. The baseline of layer N is always
+	# the painted top of layer N-1, even when that top went down.
+	func _accumulate_signed_sum(p_sample_index: int, p_scale: float) -> void:
+		var accum := 0.0
+		for series_local in range(_series_count):
+			var idx := series_local * _sample_count + p_sample_index
+			var v: float = _y_raw[idx]
+			if is_nan(v):
+				continue
+			var scaled := v * p_scale
+			_y_baseline[idx] = accum
+			accum += scaled
+			_y_plotted[idx] = accum
diff --git a/addons/tau-plot/plot/xy/stacked_series_values.gd.uid b/addons/tau-plot/plot/xy/stacked_series_values.gd.uid
new file mode 100644
index 0000000..29260d1
--- /dev/null
+++ b/addons/tau-plot/plot/xy/stacked_series_values.gd.uid
@@ -0,0 +1 @@
+uid://bse08nh8j638m
diff --git a/addons/tau-plot/plot/xy/xy_plot.gd b/addons/tau-plot/plot/xy/xy_plot.gd
index ce28090..bbd97a9 100644
--- a/addons/tau-plot/plot/xy/xy_plot.gd
+++ b/addons/tau-plot/plot/xy/xy_plot.gd
@@ -24,6 +24,8 @@ const XYDomain := preload("res://addons/tau-plot/plot/xy/xy_domain.gd").XYDomain
 const XYDomainOverrides := preload("res://addons/tau-plot/plot/xy/xy_domain_overrides.gd").XYDomainOverrides
 const YDomainOverride := preload("res://addons/tau-plot/plot/xy/xy_domain_overrides.gd").YDomainOverride
 const StackedPinnedRange := preload("res://addons/tau-plot/plot/xy/stacked_pinned_range.gd").StackedPinnedRange
+const StackedNormalization = preload("res://addons/tau-plot/plot/xy/stacked_normalization.gd").StackedNormalization
+const StackedNegativePolicy = preload("res://addons/tau-plot/plot/xy/stacked_negative_policy.gd").StackedNegativePolicy
 const XYLayout := preload("res://addons/tau-plot/plot/xy/xy_layout.gd").XYLayout
 const XYAxisTitleLayout := preload("res://addons/tau-plot/plot/xy/xy_axis_title_layout.gd").XYAxisTitleLayout
 const VisualAttributes = preload("res://addons/tau-plot/plot/xy/visual_attributes.gd").VisualAttributes
@@ -522,10 +524,10 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 
 	if has_any_bar:
 		for pane_index in range(pane_count):
-			var pane_bar_config: TauBarConfig = _bar_config_per_pane[pane_index] if pane_index < _bar_config_per_pane.size() else null
+			var pane_bar_config: TauBarConfig = _bar_config_per_pane[pane_index]
 			if pane_bar_config == null:
 				continue
-			var prev_bar_config: TauBarConfig = _state.bar_config_per_pane[pane_index] if pane_index < _state.bar_config_per_pane.size() else null
+			var prev_bar_config: TauBarConfig = _state.bar_config_per_pane[pane_index]
 			if not pane_bar_config.is_equal_to(prev_bar_config):
 				if pane_bar_config.has_layout_affecting_change(prev_bar_config):
 					_domain_dirty = true
@@ -546,10 +548,10 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 
 	if has_any_scatter:
 		for pane_index in range(pane_count):
-			var pane_scatter_config: TauScatterConfig = _scatter_config_per_pane[pane_index] if pane_index < _scatter_config_per_pane.size() else null
+			var pane_scatter_config: TauScatterConfig = _scatter_config_per_pane[pane_index]
 			if pane_scatter_config == null:
 				continue
-			var prev_scatter_config: TauScatterConfig = _state.scatter_config_per_pane[pane_index] if pane_index < _state.scatter_config_per_pane.size() else null
+			var prev_scatter_config: TauScatterConfig = _state.scatter_config_per_pane[pane_index]
 			if not pane_scatter_config.is_equal_to(prev_scatter_config):
 				if pane_scatter_config.has_layout_affecting_change(prev_scatter_config):
 					_domain_dirty = true
@@ -570,10 +572,10 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 
 	if has_any_line:
 		for pane_index in range(pane_count):
-			var pane_line_config: TauLineConfig = _line_config_per_pane[pane_index] if pane_index < _line_config_per_pane.size() else null
+			var pane_line_config: TauLineConfig = _line_config_per_pane[pane_index]
 			if pane_line_config == null:
 				continue
-			var prev_line_config: TauLineConfig = _state.line_config_per_pane[pane_index] if pane_index < _state.line_config_per_pane.size() else null
+			var prev_line_config: TauLineConfig = _state.line_config_per_pane[pane_index]
 			if not pane_line_config.is_equal_to(prev_line_config):
 				if pane_line_config.has_layout_affecting_change(prev_line_config):
 					_domain_dirty = true
@@ -641,7 +643,7 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 	# All TauBarStyle properties are visual-only, so only dirty the owning bar pane.
 	if has_any_bar:
 		for pane_index in range(pane_count):
-			var bar_config: TauBarConfig = _bar_config_per_pane[pane_index] if pane_index < _bar_config_per_pane.size() else null
+			var bar_config: TauBarConfig = _bar_config_per_pane[pane_index]
 			if bar_config == null:
 				continue
 			var needs_bar_re_resolve := _styles_dirty
@@ -653,7 +655,7 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 
 			# Content mutation: user changed a property on the existing TauBarStyle.
 			if not needs_bar_re_resolve:
-				var prev_bar_style: TauBarStyle = _state.bar_style_per_pane[pane_index] if pane_index < _state.bar_style_per_pane.size() else null
+				var prev_bar_style: TauBarStyle = _state.bar_style_per_pane[pane_index]
 				if not bar_config.style.is_equal_to(prev_bar_style):
 					needs_bar_re_resolve = true
 
@@ -669,7 +671,7 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 	# All TauScatterStyle properties are visual-only, so only dirty the owning scatter pane.
 	if has_any_scatter:
 		for pane_index in range(pane_count):
-			var scatter_config: TauScatterConfig = _scatter_config_per_pane[pane_index] if pane_index < _scatter_config_per_pane.size() else null
+			var scatter_config: TauScatterConfig = _scatter_config_per_pane[pane_index]
 			if scatter_config == null:
 				continue
 			var needs_scatter_re_resolve := _styles_dirty
@@ -681,7 +683,7 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 
 			# Content mutation: user changed a property on the existing TauScatterStyle.
 			if not needs_scatter_re_resolve:
-				var prev_scatter_style: TauScatterStyle = _state.scatter_style_per_pane[pane_index] if pane_index < _state.scatter_style_per_pane.size() else null
+				var prev_scatter_style: TauScatterStyle = _state.scatter_style_per_pane[pane_index]
 				if not scatter_config.style.is_equal_to(prev_scatter_style):
 					needs_scatter_re_resolve = true
 
@@ -697,7 +699,7 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 	# All TauLineStyle properties are visual-only, so only dirty the owning line pane.
 	if has_any_line:
 		for pane_index in range(pane_count):
-			var line_config: TauLineConfig = _line_config_per_pane[pane_index] if pane_index < _line_config_per_pane.size() else null
+			var line_config: TauLineConfig = _line_config_per_pane[pane_index]
 			if line_config == null:
 				continue
 			var needs_line_re_resolve := _styles_dirty
@@ -709,7 +711,7 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 
 			# Content mutation: user changed a property on the existing TauLineStyle.
 			if not needs_line_re_resolve:
-				var prev_line_style: TauLineStyle = _state.line_style_per_pane[pane_index] if pane_index < _state.line_style_per_pane.size() else null
+				var prev_line_style: TauLineStyle = _state.line_style_per_pane[pane_index]
 				if not line_config.style.is_equal_to(prev_line_style):
 					needs_line_re_resolve = true
 
@@ -741,7 +743,7 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 
 		# TauPaneStyle resource mutation (user changed a property on the assigned style).
 		if not needs_re_resolve:
-			var prev_pane_style: TauPaneStyle = _state.pane_style_per_pane[pane_index] if pane_index < _state.pane_style_per_pane.size() else null
+			var prev_pane_style: TauPaneStyle = _state.pane_style_per_pane[pane_index]
 			var user_style_check: TauPaneStyle = pane_config.style
 			if user_style_check != null:
 				if not user_style_check.is_equal_to(prev_pane_style):
@@ -800,9 +802,11 @@ func refresh(p_plot_global_position: Vector2, p_legend_position: Position) -> vo
 		if _hover_controller != null:
 			_hover_controller.invalidate()
 
-	# Step 5: Apply bar-specific Y overrides (stacking normalization) only if bars active
-	if _domain_dirty and has_any_bar:
-		_apply_bar_domain_overrides_y()
+	# Step 5: Apply stacking Y overrides. Bar and line stacked overlays
+	# write to the same per-axis entry, with the cross-overlay validator
+	# guaranteeing they agree on the shared fields.
+	if _domain_dirty and (has_any_bar or has_any_line):
+		_apply_stacking_domain_overrides_y()
 
 	# Step 6: Recompute domain from dataset if needed
 	if _domain_dirty:
@@ -1146,52 +1150,75 @@ func _update_xy_layout(p_pane_view_rects: Array[Rect2], p_pane_positions: Array[
 	_xy_layout.update()
 
 
-func _apply_bar_domain_overrides_y() -> void:
+func _apply_stacking_domain_overrides_y() -> void:
 	var pane_count := _domain_config.panes.size()
 	for pane_index in range(pane_count):
 		_xy_domain_overrides.clear_pane(pane_index)
+		_apply_bar_stacking_for_pane(pane_index)
+		_apply_line_stacking_for_pane(pane_index)
 
-		if pane_index >= _bar_series_ids_per_pane.size():
-			continue
-		if _bar_series_ids_per_pane[pane_index].is_empty():
-			continue
 
-		var pane_bar_config: TauBarConfig = _bar_config_per_pane[pane_index] if pane_index < _bar_config_per_pane.size() else null
-		if pane_bar_config == null:
-			continue
+func _apply_bar_stacking_for_pane(p_pane_index: int) -> void:
+	if _bar_series_ids_per_pane[p_pane_index].is_empty():
+		return
 
-		if pane_bar_config.mode != TauBarConfig.BarMode.STACKED:
-			continue
+	var pane_bar_config: TauBarConfig = _bar_config_per_pane[p_pane_index]
+	if pane_bar_config.mode != TauBarConfig.BarMode.STACKED:
+		return
 
-		# Resolve the y-axis actually used by the stacked bar series.
-		# The validator enforces that all stacked bar series share the same y_axis_id,
-		# so checking the first one is enough.
-		var first_bar_sid: int = _bar_series_ids_per_pane[pane_index][0]
-		var stacked_y_axis_id: int = _series_assignment.get_y_axis_id_for_series(first_bar_sid, pane_index)
-		if stacked_y_axis_id == -1:
-			continue
+	# Stacked bar series in a pane share one y axis, so any series id resolves it.
+	var first_bar_sid: int = _bar_series_ids_per_pane[p_pane_index][0]
+	var stacked_y_axis_id: int = _series_assignment.get_y_axis_id_for_series(first_bar_sid, p_pane_index)
 
-		# Only check the axis that the stacked bars are bound to.
-		var pane_config: TauPaneConfig = _domain_config.panes[pane_index]
-		var stacked_y_cfg: TauAxisConfig = pane_config.get_y_axis_config(stacked_y_axis_id)
-		if stacked_y_cfg != null and stacked_y_cfg.range_override_enabled:
-			continue
+	var pane_config: TauPaneConfig = _domain_config.panes[p_pane_index]
+	var stacked_y_cfg: TauAxisConfig = pane_config.get_y_axis_config(stacked_y_axis_id)
+	# An explicit user range wins over any stacking-driven range.
+	if stacked_y_cfg.range_override_enabled:
+		return
 
-		var y_domain_override: YDomainOverride = _xy_domain_overrides.get_or_create_override(pane_index, stacked_y_axis_id)
+	var y_domain_override: YDomainOverride = _xy_domain_overrides.get_or_create_override(p_pane_index, stacked_y_axis_id)
 
-		y_domain_override.bar_stack_active = true
-		y_domain_override.stacked_normalization = pane_bar_config.stacked_normalization
-		y_domain_override.stacked_negative_policy = pane_bar_config.stacked_negative_policy
+	y_domain_override.bar_stack_active = true
+	y_domain_override.stacked_normalization = pane_bar_config.stacked_normalization
+	y_domain_override.stacked_negative_policy = pane_bar_config.stacked_negative_policy
 
-		match pane_bar_config.stacked_normalization:
-			TauBarConfig.StackedNormalization.NONE:
-				pass
+	_apply_pinned_range(y_domain_override, pane_bar_config.stacked_normalization, pane_bar_config.stacked_negative_policy)
 
-			TauBarConfig.StackedNormalization.FRACTION, TauBarConfig.StackedNormalization.PERCENT:
-				var pinned := StackedPinnedRange.compute(pane_bar_config.stacked_normalization, pane_bar_config.stacked_negative_policy)
-				y_domain_override.force_y_range = true
-				y_domain_override.force_y_min = pinned.x
-				y_domain_override.force_y_max = pinned.y
 
-			_:
-				push_error("_apply_bar_domain_overrides_y(): unexpected stacked normalization")
+func _apply_line_stacking_for_pane(p_pane_index: int) -> void:
+	if _line_series_ids_per_pane[p_pane_index].is_empty():
+		return
+
+	var pane_line_config: TauLineConfig = _line_config_per_pane[p_pane_index]
+	if pane_line_config.mode != TauLineConfig.LineMode.STACKED:
+		return
+
+	# Stacked line series in a pane share one y axis, so any series id resolves it.
+	var first_line_sid: int = _line_series_ids_per_pane[p_pane_index][0]
+	var stacked_y_axis_id: int = _series_assignment.get_y_axis_id_for_series(first_line_sid, p_pane_index)
+
+	var pane_config: TauPaneConfig = _domain_config.panes[p_pane_index]
+	var stacked_y_cfg: TauAxisConfig = pane_config.get_y_axis_config(stacked_y_axis_id)
+	# An explicit user range wins over any stacking-driven range.
+	if stacked_y_cfg.range_override_enabled:
+		return
+
+	var y_domain_override: YDomainOverride = _xy_domain_overrides.get_or_create_override(p_pane_index, stacked_y_axis_id)
+
+	y_domain_override.line_stack_active = true
+	y_domain_override.stacked_normalization = pane_line_config.stacked_normalization
+	y_domain_override.stacked_negative_policy = pane_line_config.stacked_negative_policy
+
+	_apply_pinned_range(y_domain_override, pane_line_config.stacked_normalization, pane_line_config.stacked_negative_policy)
+
+
+# NONE keeps the range data-driven. FRACTION and PERCENT need a fixed
+# range so every per-X stack fits exactly the available space.
+func _apply_pinned_range(p_override: YDomainOverride,
+		p_normalization: StackedNormalization, p_policy: StackedNegativePolicy) -> void:
+	if p_normalization == StackedNormalization.NONE:
+		return
+	var pinned := StackedPinnedRange.compute(p_normalization, p_policy)
+	p_override.force_y_range = true
+	p_override.force_y_min = pinned.x
+	p_override.force_y_max = pinned.y
diff --git a/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd
index 6b6675e..c164b3c 100644
--- a/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd
+++ b/addons/tau-plot/tests/bar/stacked/test_bar_stacked_negative_none.gd
@@ -35,6 +35,7 @@ func _setup_test_1() -> void:
 	var y_axis := TauAxisConfig.new()
 	y_axis.type = TauAxisConfig.Type.CONTINUOUS
 	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 15
 
 	var bar_config := TauBarConfig.new()
 	bar_config.mode = TauBarConfig.BarMode.STACKED
@@ -94,6 +95,7 @@ func _setup_test_2() -> void:
 	var y_axis := TauAxisConfig.new()
 	y_axis.type = TauAxisConfig.Type.CONTINUOUS
 	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 20
 
 	var bar_config := TauBarConfig.new()
 	bar_config.mode = TauBarConfig.BarMode.STACKED
@@ -161,6 +163,7 @@ func _setup_test_4() -> void:
 	bar_config.mode = TauBarConfig.BarMode.STACKED
 	bar_config.stacked_normalization = TauBarConfig.StackedNormalization.NONE
 	bar_config.stacked_negative_policy = TauBarConfig.StackedNegativePolicy.SKIP_NEGATIVES
+	y_axis.tick_count_preferred = 15
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -211,6 +214,7 @@ func _setup_test_5() -> void:
 	var y_axis := TauAxisConfig.new()
 	y_axis.type = TauAxisConfig.Type.CONTINUOUS
 	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 20
 
 	var bar_config := TauBarConfig.new()
 	bar_config.mode = TauBarConfig.BarMode.STACKED
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd
new file mode 100644
index 0000000..35213a6
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd
@@ -0,0 +1,351 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot1.title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.FRACTION
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SKIP_NEGATIVES
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot2.title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.FRACTION
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot3.title = "[CONTINUOUS] with stacked_negative_policy = SIGNED_SUM"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.FRACTION
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SIGNED_SUM
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot3.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot4.title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.FRACTION
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SKIP_NEGATIVES
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot4.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot5.title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.FRACTION
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot5.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot6.title = "[CATEGORICAL] with stacked_negative_policy = SIGNED_SUM"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.FRACTION
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SIGNED_SUM
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot6.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd.uid b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd.uid
new file mode 100644
index 0000000..8712f17
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd.uid
@@ -0,0 +1 @@
+uid://t5fdpmq6toqn
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.tscn b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.tscn
new file mode 100644
index 0000000..e6c96b9
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.tscn
@@ -0,0 +1,85 @@
+[gd_scene load_steps=3 format=3 uid="uid://dfulk3tfeosmh"]
+
+[ext_resource type="Script" uid="uid://t5fdpmq6toqn" path="res://addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd" id="1_kstpx"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_71bbx"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_kstpx")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test stacked bars negative policy with normalization = FRACTION"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_71bbx")
+title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_71bbx")
+title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_71bbx")
+title = "[CONTINUOUS] with stacked_negative_policy = SIGNED_SUM"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_71bbx")
+title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_71bbx")
+title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_71bbx")
+title = "[CATEGORICAL] with stacked_negative_policy = SIGNED_SUM"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd
new file mode 100644
index 0000000..a4f44c6
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd
@@ -0,0 +1,358 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot1.title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.NONE
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SKIP_NEGATIVES
+	#line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot2.title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.NONE
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot3.title = "[CONTINUOUS] with stacked_negative_policy = SIGNED_SUM"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.NONE
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SIGNED_SUM
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot3.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot4.title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.NONE
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SKIP_NEGATIVES
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot4.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot5.title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.NONE
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot5.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot6.title = "[CATEGORICAL] with stacked_negative_policy = SIGNED_SUM"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.NONE
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SIGNED_SUM
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot6.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd.uid b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd.uid
new file mode 100644
index 0000000..d2952f7
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd.uid
@@ -0,0 +1 @@
+uid://gq3klvlipxkr
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.tscn b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.tscn
new file mode 100644
index 0000000..34ff9ea
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.tscn
@@ -0,0 +1,85 @@
+[gd_scene load_steps=3 format=3 uid="uid://ede28c5yqix3"]
+
+[ext_resource type="Script" uid="uid://gq3klvlipxkr" path="res://addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd" id="1_t3a0d"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_q7rrf"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_t3a0d")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test stacked bars negative policy with normalization = NONE"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_q7rrf")
+title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_q7rrf")
+title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_q7rrf")
+title = "[CONTINUOUS] with stacked_negative_policy = SIGNED_SUM"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_q7rrf")
+title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_q7rrf")
+title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_q7rrf")
+title = "[CATEGORICAL] with stacked_negative_policy = SIGNED_SUM"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd
new file mode 100644
index 0000000..87d8014
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd
@@ -0,0 +1,351 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot1.title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.PERCENT
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SKIP_NEGATIVES
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot2.title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.PERCENT
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot3.title = "[CONTINUOUS] with stacked_negative_policy = SIGNED_SUM"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.PERCENT
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SIGNED_SUM
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot3.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot4.title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.PERCENT
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SKIP_NEGATIVES
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot4.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot5.title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.PERCENT
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.DIVERGING
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot5.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 5.0, 15.0, 5.0, 10.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, -20.0, 30.0, 25.0])
+	var y_c := PackedFloat64Array([20.0, 30.0, 40.0, 30.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot6.title = "[CATEGORICAL] with stacked_negative_policy = SIGNED_SUM"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.PERCENT
+	line_config.stacked_negative_policy = TauLineConfig.StackedNegativePolicy.SIGNED_SUM
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b, sb_c]
+
+	%TestPlot6.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd.uid b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd.uid
new file mode 100644
index 0000000..cd2cc01
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd.uid
@@ -0,0 +1 @@
+uid://bpbp8mimvrtki
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.tscn b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.tscn
new file mode 100644
index 0000000..bd41d1e
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.tscn
@@ -0,0 +1,83 @@
+[gd_scene load_steps=3 format=3 uid="uid://sifkw67vbj2h"]
+
+[ext_resource type="Script" uid="uid://bpbp8mimvrtki" path="res://addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd" id="1_os7bv"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_tcxo6"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_os7bv")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test stacked bars negative policy with normalization = PERCENT"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_tcxo6")
+title = "[CONTINUOUS] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_tcxo6")
+title = "[CONTINUOUS] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_tcxo6")
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_tcxo6")
+title = "[CATEGORICAL] with stacked_negative_policy = SKIP_NEGATIVES"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_tcxo6")
+title = "[CATEGORICAL] with stacked_negative_policy = DIVERGING"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_tcxo6")
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd b/addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd
new file mode 100644
index 0000000..06f2d48
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd
@@ -0,0 +1,349 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot1.title = "[CONTINUOUS] with stacked_normalization = NONE"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.NONE
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_c, sb_a, sb_b]
+
+	%TestPlot1.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot2.title = "[CONTINUOUS] with stacked_normalization = FRACTION"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.FRACTION
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_b, sb_a, sb_c]
+
+	%TestPlot2.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot3.title = "[CONTINUOUS] with stacked_normalization = PERCENT"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+	x_axis.domain_padding_mode = TauAxisConfig.DomainPaddingMode.DATA_UNITS
+	x_axis.domain_padding_min = 0.5
+	x_axis.domain_padding_max = 0.5
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.format_tick_label = func(label: String) -> String:
+		return label + "%"
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.PERCENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_c, sb_b]
+
+	%TestPlot3.plot_xy(dataset, config, bindings)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four"])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot4.title = "[CATEGORICAL] with stacked_normalization = NONE"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.NONE
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_b, sb_a, sb_c]
+
+	%TestPlot4.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four"])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot5.title = "[CATEGORICAL] with stacked_normalization = FRACTION"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.FRACTION
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_c, sb_a, sb_b]
+
+	%TestPlot5.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	var series_names := PackedStringArray(["Series A", "Series B", "Series C"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four"])
+	var y_a := PackedFloat64Array([5.0, 10.0, 15.0, 20.0])
+	var y_b := PackedFloat64Array([25.0, 30.0, 35.0, 40.0])
+	var y_c := PackedFloat64Array([30.0, 40.0, 50.0, 60.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b, y_c])
+
+	%TestPlot6.title = "[CATEGORICAL] with stacked_normalization = PERCENT"
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.format_tick_label = func(label: String) -> String:
+		return label + "%"
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.STACKED
+	line_config.stacked_normalization = TauLineConfig.StackedNormalization.PERCENT
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_c := TauXYSeriesBinding.new()
+	sb_c.series_id = dataset.get_series_id_by_index(2)
+	sb_c.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_c.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_b, sb_c, sb_a]
+
+	%TestPlot6.plot_xy(dataset, config, bindings)
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd.uid b/addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd.uid
new file mode 100644
index 0000000..b7a4833
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd.uid
@@ -0,0 +1 @@
+uid://cc44m4dwx745i
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacking_order.tscn b/addons/tau-plot/tests/line/stacked/test_line_stacking_order.tscn
new file mode 100644
index 0000000..47a2ab1
--- /dev/null
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacking_order.tscn
@@ -0,0 +1,85 @@
+[gd_scene load_steps=3 format=3 uid="uid://dg287kd0yxvbr"]
+
+[ext_resource type="Script" uid="uid://cc44m4dwx745i" path="res://addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd" id="1_if76y"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_e36ro"]
+
+[node name="Bars" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_if76y")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Test stacking order which is dataset order, not binding order."
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_e36ro")
+title = "[CONTINUOUS] with stacked_normalization = NONE"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_e36ro")
+title = "[CONTINUOUS] with stacked_normalization = FRACTION"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_e36ro")
+title = "[CONTINUOUS] with stacked_normalization = PERCENT"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_e36ro")
+title = "[CATEGORICAL] with stacked_normalization = NONE"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_e36ro")
+title = "[CATEGORICAL] with stacked_normalization = FRACTION"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_e36ro")
+title = "[CATEGORICAL] with stacked_normalization = PERCENT"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"

From 3ab40d4322cb805d6e78c3d55ae93a37ad63ca33 Mon Sep 17 00:00:00 2001
From: ze2j <46556066+ze2j@users.noreply.github.com>
Date: Wed, 13 May 2026 00:06:18 +0200
Subject: [PATCH 23/23] Fill to baseline

---
 addons/tau-plot/plot/xy/line/line_config.gd   |  35 +++
 addons/tau-plot/plot/xy/line/line_renderer.gd | 199 ++++++++++--
 addons/tau-plot/plot/xy/line/line_style.gd    |  75 ++++-
 .../tau-plot/plot/xy/line/line_validator.gd   |  16 +
 .../line/area/test_line_fill_color_alpha.gd   | 285 ++++++++++++++++++
 .../area/test_line_fill_color_alpha.gd.uid    |   1 +
 .../line/area/test_line_fill_color_alpha.tscn | 185 ++++++++++++
 .../tests/line/area/test_line_fill_linear.gd  | 279 +++++++++++++++++
 .../line/area/test_line_fill_linear.gd.uid    |   1 +
 .../line/area/test_line_fill_linear.tscn      | 185 ++++++++++++
 .../line/area/test_line_fill_logarithmic.gd   | 276 +++++++++++++++++
 .../area/test_line_fill_logarithmic.gd.uid    |   1 +
 .../line/area/test_line_fill_logarithmic.tscn | 185 ++++++++++++
 .../tests/line/dash/test_line_dash.tscn       |   2 +-
 .../test_line_interpolation_linear.tscn       |   2 +-
 .../test_line_interpolation_logarithmic.tscn  |   2 +-
 ...est_line_visual_attributes_dash_alpha.tscn |   2 +-
 ...est_line_visual_attributes_dash_color.tscn |   2 +-
 ...st_line_visual_attributes_solid_alpha.tscn |   2 +-
 ...st_line_visual_attributes_solid_color.tscn |   2 +-
 ...test_line_visual_callbacks_dash_alpha.tscn |   2 +-
 ...test_line_visual_callbacks_dash_color.tscn |   2 +-
 ...est_line_visual_callbacks_solid_alpha.tscn |   2 +-
 ...est_line_visual_callbacks_solid_color.tscn |   2 +-
 .../line/log_scale/test_line_logarithmic.tscn |   2 +-
 .../nan_or_inf/test_line_nan_inf_bridge.gd    |  16 +
 .../nan_or_inf/test_line_nan_inf_bridge.tscn  |  18 +-
 .../line/nan_or_inf/test_line_nan_inf_skip.gd |  16 +
 .../nan_or_inf/test_line_nan_inf_skip.tscn    |   2 +-
 .../test_line_stacked_negative_fraction.tscn  |   2 +-
 .../test_line_stacked_negative_none.tscn      |   2 +-
 .../test_line_stacked_negative_percent.tscn   |   4 +-
 .../stacked/test_line_stacking_order.tscn     |   2 +-
 33 files changed, 1752 insertions(+), 57 deletions(-)
 create mode 100644 addons/tau-plot/tests/line/area/test_line_fill_color_alpha.gd
 create mode 100644 addons/tau-plot/tests/line/area/test_line_fill_color_alpha.gd.uid
 create mode 100644 addons/tau-plot/tests/line/area/test_line_fill_color_alpha.tscn
 create mode 100644 addons/tau-plot/tests/line/area/test_line_fill_linear.gd
 create mode 100644 addons/tau-plot/tests/line/area/test_line_fill_linear.gd.uid
 create mode 100644 addons/tau-plot/tests/line/area/test_line_fill_linear.tscn
 create mode 100644 addons/tau-plot/tests/line/area/test_line_fill_logarithmic.gd
 create mode 100644 addons/tau-plot/tests/line/area/test_line_fill_logarithmic.gd.uid
 create mode 100644 addons/tau-plot/tests/line/area/test_line_fill_logarithmic.tscn

diff --git a/addons/tau-plot/plot/xy/line/line_config.gd b/addons/tau-plot/plot/xy/line/line_config.gd
index e9e362b..d109c28 100644
--- a/addons/tau-plot/plot/xy/line/line_config.gd
+++ b/addons/tau-plot/plot/xy/line/line_config.gd
@@ -78,6 +78,37 @@ enum InterpolationMode
 }
 @export var interpolation_mode: InterpolationMode = InterpolationMode.LINEAR
 
+## Strategy applied to fill the area between the line and a reference
+## baseline. The visual appearance of the fill is controlled by
+## [TauLineStyle].
+##
+## NONE leaves the area below the line unfilled.
+##
+## TO_BASELINE fills the area between the line and the constant value
+## [member fill_baseline]. When the curve crosses the baseline between two
+## consecutive samples, the fill is split into multiple sub-polygons at the
+## crossings, one per same-side run.
+##
+## STACKED is only meaningful when [member mode] is STACKED. Each stacked
+## layer is filled between its own curve and the top of the layer below.
+## The bottom layer is filled down to y = 0.
+##
+## This property is visual-only and does not affect layout or domain.
+enum FillMode
+{
+	NONE,           ## No area is filled.
+	TO_BASELINE,    ## Fill between the line and [member fill_baseline].
+	STACKED         ## Fill each stacked layer between its curve and the layer below.
+}
+@export var fill_mode: FillMode = FillMode.NONE
+
+## Y value used as the reference baseline when [member fill_mode] is
+## TO_BASELINE. Expressed in data units on the series y-axis. Ignored for
+## any other [member fill_mode] value.
+##
+## This property is visual-only and does not affect layout or domain.
+@export var fill_baseline: float = 0.0
+
 ## Maximum pixel distance from the cursor to a sample position for the sample
 ## to be considered a hover hit.
 ##
@@ -130,6 +161,10 @@ func is_equal_to(p_other: TauPaneOverlayConfig) -> bool:
 		return false
 	if interpolation_mode != other.interpolation_mode:
 		return false
+	if fill_mode != other.fill_mode:
+		return false
+	if fill_baseline != other.fill_baseline:
+		return false
 	if hover_max_distance_px != other.hover_max_distance_px:
 		return false
 
diff --git a/addons/tau-plot/plot/xy/line/line_renderer.gd b/addons/tau-plot/plot/xy/line/line_renderer.gd
index 1c324d3..3e1bd15 100644
--- a/addons/tau-plot/plot/xy/line/line_renderer.gd
+++ b/addons/tau-plot/plot/xy/line/line_renderer.gd
@@ -86,6 +86,19 @@ const StackedSeriesValues := preload("res://addons/tau-plot/plot/xy/stacked_seri
 # - LineHitRecord.y_plotted_value carries the cumulative top.
 #   LineHitRecord.y_raw_value carries the original dataset value.
 #
+# Area fill:
+# - When TauLineConfig.fill_mode is TO_BASELINE, the area between the line
+#   and the constant TauLineConfig.fill_baseline is filled before the line
+#   is drawn. The polygon is built from the rendered polyline (after
+#   interpolation has materialized any synthetic vertices) and is split at
+#   every baseline crossing into same-side sub-polygons, each emitted as
+#   one draw_colored_polygon call. The line itself is unaffected by the
+#   split and remains one draw call per contiguous run.
+# - Fill color resolution: when TauLineStyle.fill_color is the sentinel
+#   Color(0, 0, 0, 0), the per-series color from TauXYStyle.series_colors
+#   is used. Otherwise the flat TauLineStyle.fill_color wins. The resolved
+#   color's alpha channel is multiplied by TauLineStyle.fill_alpha.
+#
 # LineValidator is expected to enforce binding-level typing constraints.
 class LineRenderer extends Control:
 	# Number of sub-segments inserted between two consecutive samples by
@@ -207,25 +220,17 @@ class LineRenderer extends Control:
 	func _draw() -> void:
 		_hit_records.clear()
 
-		if _line_style == null:
-			push_error("LineRenderer: resolved TauLineStyle is null.")
-			return
-
 		var pane_rect := _layout.get_pane_rect(_pane_index)
 		if pane_rect.size.x <= 0.0 or pane_rect.size.y <= 0.0:
 			return
 
-		var series_count := _get_line_series_count()
-		if series_count <= 0:
-			return
-
 		var stacked_values: StackedSeriesValues = null
 		if _line_config.mode == TauLineConfig.LineMode.STACKED:
 			stacked_values = StackedSeriesValues.new(_dataset, _line_series_ids,
 					_line_config.stacked_normalization,
 					_line_config.stacked_negative_policy)
 
-		var draw_order := _get_series_draw_order(series_count)
+		var draw_order := _get_series_draw_order(_get_line_series_count())
 		for draw_rank in range(draw_order.size()):
 			var series_index: int = draw_order[draw_rank]
 			_draw_series(series_index, stacked_values)
@@ -240,8 +245,7 @@ class LineRenderer extends Control:
 	#     - BRIDGE drops the sample and keeps appending into the same run.
 	#   - A run of fewer than two points is discarded.
 	func _draw_series(p_series_index: int, p_stacked: StackedSeriesValues) -> void:
-		var x_cfg := _get_x_axis_config()
-		if x_cfg != null and x_cfg.type == TauAxisConfig.Type.CATEGORICAL:
+		if _get_x_axis_config().type == TauAxisConfig.Type.CATEGORICAL:
 			_draw_series_categorical(p_series_index, p_stacked)
 		else:
 			_draw_series_continuous(p_series_index, p_stacked)
@@ -259,6 +263,11 @@ class LineRenderer extends Control:
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
 
+		# Resolved once per series: every run of this series fills against the
+		# same baseline and the same color.
+		var fill_color: Color = _resolve_series_fill_color(global_series_index)
+		var baseline_y_px: float = _resolve_fill_baseline_y_px(y_axis_id)
+
 		var independent_y: PackedFloat64Array
 		if p_stacked == null:
 			independent_y = _build_independent_y_row(series_id)
@@ -280,7 +289,7 @@ class LineRenderer extends Control:
 			var x_value: float = float(_dataset.get_shared_x(i)) if is_shared_x else float(_dataset.get_series_x(series_id, i))
 			if is_nan(x_value) or is_inf(x_value) or not _is_x_value_valid_for_scale(x_value):
 				if not bridge:
-					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
+					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px, fill_color, baseline_y_px)
 					run = PackedVector2Array()
 					run_colors = PackedColorArray()
 					real_polyline_indices = PackedInt32Array()
@@ -298,7 +307,7 @@ class LineRenderer extends Control:
 
 			if is_nan(y_plotted):
 				if not bridge:
-					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
+					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px, fill_color, baseline_y_px)
 					run = PackedVector2Array()
 					run_colors = PackedColorArray()
 					real_polyline_indices = PackedInt32Array()
@@ -324,7 +333,7 @@ class LineRenderer extends Control:
 			record.screen_position = screen_pos
 			_hit_records.append(record)
 
-		_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
+		_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px, fill_color, baseline_y_px)
 
 
 	func _draw_series_categorical(p_series_index: int, p_stacked: StackedSeriesValues) -> void:
@@ -339,6 +348,11 @@ class LineRenderer extends Control:
 		var bridge: bool = _line_config.gap_policy == TauLineConfig.GapPolicy.BRIDGE
 		var interpolation: TauLineConfig.InterpolationMode = _line_config.interpolation_mode
 
+		# Resolved once per series: every run of this series fills against the
+		# same baseline and the same color.
+		var fill_color: Color = _resolve_series_fill_color(global_series_index)
+		var baseline_y_px: float = _resolve_fill_baseline_y_px(y_axis_id)
+
 		var independent_y: PackedFloat64Array
 		if p_stacked == null:
 			independent_y = _build_independent_y_row(series_id)
@@ -362,7 +376,7 @@ class LineRenderer extends Control:
 
 			if is_nan(y_plotted):
 				if not bridge:
-					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
+					_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px, fill_color, baseline_y_px)
 					run = PackedVector2Array()
 					run_colors = PackedColorArray()
 					real_polyline_indices = PackedInt32Array()
@@ -387,7 +401,7 @@ class LineRenderer extends Control:
 			record.screen_position = screen_pos
 			_hit_records.append(record)
 
-		_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px)
+		_finalize_run(run, run_colors, real_polyline_indices, real_dataset_indices, series_id, width_px, hover_width_px, interpolation, dash_px, fill_color, baseline_y_px)
 
 
 	# Marks dropped samples (NaN, Inf, log-axis violations) as NAN up front
@@ -443,6 +457,12 @@ class LineRenderer extends Control:
 	# For SMOOTH_MONOTONE the run is first replaced by its Fritsch-Carlson piecewise cubic resampling.
 	# Runs of fewer than two points are silently dropped.
 	#
+	# When p_fill_color has non-zero alpha and p_baseline_y_px is finite,
+	# the area between the rendered polyline and the horizontal baseline
+	# is filled before the line is drawn. The polygon is split at every
+	# baseline crossing into same-side sub-polygons, each emitted as one
+	# draw call. The line itself is unaffected by splitting.
+	#
 	# Path selection per series (no hover):
 	#   - p_dash_px == 0: one draw_polyline_colors call.
 	#   - p_dash_px  > 0: one draw_multiline_colors call after dash precomputation.
@@ -466,7 +486,7 @@ class LineRenderer extends Control:
 	# real_polyline_indices[k] is the index in p_run where the k-th real
 	# sample landed. real_dataset_indices[k] is the dataset sample index for
 	# that real sample.
-	func _finalize_run(p_run: PackedVector2Array, p_run_colors: PackedColorArray, p_real_polyline_indices: PackedInt32Array, p_real_dataset_indices: PackedInt32Array, p_series_id: int, p_width_px: float, p_hover_width_px: float, p_mode: TauLineConfig.InterpolationMode, p_dash_px: int) -> void:
+	func _finalize_run(p_run: PackedVector2Array, p_run_colors: PackedColorArray, p_real_polyline_indices: PackedInt32Array, p_real_dataset_indices: PackedInt32Array, p_series_id: int, p_width_px: float, p_hover_width_px: float, p_mode: TauLineConfig.InterpolationMode, p_dash_px: int, p_fill_color: Color, p_baseline_y_px: float) -> void:
 		var polyline: PackedVector2Array = p_run
 		var polyline_colors: PackedColorArray = p_run_colors
 		var real_polyline_indices: PackedInt32Array = p_real_polyline_indices
@@ -481,6 +501,11 @@ class LineRenderer extends Control:
 		if polyline.size() < 2:
 			return
 
+		# Fill is drawn first so the polyline lands on top of it. A NaN
+		# baseline or zero-alpha color means no fill for this run.
+		if not is_nan(p_baseline_y_px) and p_fill_color.a > 0.0:
+			_draw_fill_to_baseline(polyline, p_fill_color, p_baseline_y_px)
+
 		var dash_px: int = max(p_dash_px, 0)
 		var slice_bounds := _resolve_hover_slice_bounds(real_polyline_indices, p_real_dataset_indices, p_series_id)
 
@@ -678,6 +703,133 @@ class LineRenderer extends Control:
 		if segments.size() >= 2:
 			draw_multiline_colors(segments, segment_colors, p_width_px)
 
+	####################################################################################################
+	# Area fill
+	####################################################################################################
+
+	# Resolves the per-series flat fill color, or fully transparent when no
+	# flat fill applies. Only TO_BASELINE produces a flat fill polygon. NONE
+	# leaves the area below the line unfilled, and STACKED is handled by the
+	# per-layer fill path rather than per-run flat fill.
+	func _resolve_series_fill_color(p_global_series_index: int) -> Color:
+		if _line_config.fill_mode != TauLineConfig.FillMode.TO_BASELINE:
+			return Color(0, 0, 0, 0)
+		return _line_style.get_series_fill_color(p_global_series_index, _xy_style)
+
+
+	# Returns the screen-space Y coordinate of the TO_BASELINE baseline, or
+	# NAN when no flat baseline applies.
+	func _resolve_fill_baseline_y_px(p_y_axis_id: AxisId) -> float:
+		if _line_config.fill_mode != TauLineConfig.FillMode.TO_BASELINE:
+			return NAN
+		var y_px: float = _layout.map_y_to_px(_pane_index, _line_config.fill_baseline, p_y_axis_id)
+		var screen_pos: Vector2 = _layout.map_point_to_screen(0.0, y_px)
+		return screen_pos.y
+
+
+	# Builds and draws the fill polygon between p_polyline and the horizontal
+	# line y = p_baseline_y_px in screen space. The polygon is split at every
+	# baseline crossing, producing one sub-polygon per same-side run, each
+	# emitted as a single draw_colored_polygon call.
+	#
+	# Crossing detection runs on the rendered polyline, so the synthetic
+	# vertices inserted by step interpolation and the sub-samples emitted by
+	# SMOOTH_MONOTONE are treated uniformly. A crossing point lies at the
+	# linear interpolation of the two flanking polyline vertices against
+	# the baseline. Both polyline orderings (ascending or descending screen
+	# X) are accepted because the builder never assumes a direction.
+	func _draw_fill_to_baseline(p_polyline: PackedVector2Array, p_fill_color: Color, p_baseline_y_px: float) -> void:
+		var n: int = p_polyline.size()
+		if n < 2:
+			return
+
+		# Same-side accumulator. The current sub-polygon's top edge is the
+		# vertices buffered in `top`. `side` is the sign of (y - baseline_y)
+		# for the first non-on-baseline vertex of the run, and stays 0 until
+		# one is found. On-baseline vertices are appended to `top` and do
+		# not constrain `side`.
+		var top := PackedVector2Array()
+		var side: int = 0
+
+		for i in range(n):
+			var v: Vector2 = p_polyline[i]
+			var v_side: int = _baseline_side(v.y, p_baseline_y_px)
+
+			if top.is_empty():
+				top.append(v)
+				side = v_side
+				continue
+
+			# Treat on-baseline as a degenerate crossing: the vertex sits on
+			# both half-planes, so it can extend the current run AND open a
+			# new one without a synthetic crossing.
+			if v_side == 0 or side == 0 or v_side == side:
+				top.append(v)
+				if side == 0:
+					side = v_side
+				continue
+
+			# v_side and side are non-zero and opposite: a real crossing
+			# between top[-1] and v. The crossing point closes the current
+			# sub-polygon and seeds the next one.
+			var prev: Vector2 = top[top.size() - 1]
+			var crossing: Vector2 = _baseline_crossing(prev, v, p_baseline_y_px)
+			top.append(crossing)
+			_emit_fill_subpolygon(top, p_fill_color, p_baseline_y_px)
+			top = PackedVector2Array()
+			top.append(crossing)
+			top.append(v)
+			side = v_side
+
+		_emit_fill_subpolygon(top, p_fill_color, p_baseline_y_px)
+
+
+	# Closes one sub-polygon by dropping its endpoints to the baseline and
+	# hands it to draw_colored_polygon. Runs that contain fewer than two
+	# points or that are entirely on the baseline contribute no area and
+	# are skipped.
+	func _emit_fill_subpolygon(p_top: PackedVector2Array, p_fill_color: Color, p_baseline_y_px: float) -> void:
+		var top_count: int = p_top.size()
+		if top_count < 2:
+			return
+		# A run sitting exactly on the baseline has zero area.
+		var any_off_baseline: bool = false
+		for k in range(top_count):
+			if p_top[k].y != p_baseline_y_px:
+				any_off_baseline = true
+				break
+		if not any_off_baseline:
+			return
+
+		var polygon := PackedVector2Array()
+		polygon.resize(top_count + 2)
+		# Top edge in forward order, then closing edge down to the baseline.
+		for k in range(top_count):
+			polygon[k] = p_top[k]
+		polygon[top_count] = Vector2(p_top[top_count - 1].x, p_baseline_y_px)
+		polygon[top_count + 1] = Vector2(p_top[0].x, p_baseline_y_px)
+		draw_colored_polygon(polygon, p_fill_color)
+
+
+	# Returns +1 above the baseline (smaller screen Y), -1 below, 0 on it.
+	# Screen space is Y-down so "above the baseline in data space" means
+	# "smaller Y in screen space".
+	static func _baseline_side(p_y: float, p_baseline_y: float) -> int:
+		if p_y < p_baseline_y:
+			return 1
+		if p_y > p_baseline_y:
+			return -1
+		return 0
+
+
+	# Linear interpolation along segment (p_a, p_b) at the parameter where
+	# y reaches p_baseline_y. Precondition: p_a.y and p_b.y straddle
+	# p_baseline_y with a non-zero gap, which is guaranteed by the caller.
+	static func _baseline_crossing(p_a: Vector2, p_b: Vector2, p_baseline_y: float) -> Vector2:
+		var t: float = (p_baseline_y - p_a.y) / (p_b.y - p_a.y)
+		return Vector2(p_a.x + t * (p_b.x - p_a.x), p_baseline_y)
+
+
 	####################################################################################################
 	# Smooth-monotone (Fritsch-Carlson) resampling
 	####################################################################################################
@@ -1046,20 +1198,11 @@ class LineRenderer extends Control:
 	####################################################################################################
 
 	func _is_x_value_valid_for_scale(p_x_value: float) -> bool:
-		var x_cfg := _layout.domain.config.x_axis
-		if x_cfg == null:
-			return true
-		if x_cfg.scale == TauAxisConfig.Scale.LOGARITHMIC and p_x_value <= 0.0:
-			return false
-		return true
+		return _layout.domain.config.x_axis.scale != TauAxisConfig.Scale.LOGARITHMIC or p_x_value > 0.0
 
 
 	func _is_y_value_valid_for_scale(p_series_id: int, p_y_value: float) -> bool:
 		var y_axis_id := _get_y_axis_id_for_series(p_series_id)
 		var pane_cfg: TauPaneConfig = _layout.domain.config.panes[_pane_index]
 		var y_cfg: TauAxisConfig = pane_cfg.get_y_axis_config(y_axis_id)
-		if y_cfg == null:
-			return true
-		if y_cfg.scale == TauAxisConfig.Scale.LOGARITHMIC and p_y_value <= 0.0:
-			return false
-		return true
+		return y_cfg.scale != TauAxisConfig.Scale.LOGARITHMIC or p_y_value > 0.0
diff --git a/addons/tau-plot/plot/xy/line/line_style.gd b/addons/tau-plot/plot/xy/line/line_style.gd
index 4b2b486..f292938 100644
--- a/addons/tau-plot/plot/xy/line/line_style.gd
+++ b/addons/tau-plot/plot/xy/line/line_style.gd
@@ -50,6 +50,24 @@ const DEFAULT_HOVERED_LINE_WIDTHS_PX: Array[float] = [3.0]
 const DEFAULT_DASH_LENGTHS_PX: Array[int] = [0]
 @export var dash_lengths_px: Array[int] = [0]
 
+## Flat color applied to the area defined by [member TauLineConfig.fill_mode].
+## The sentinel [code]Color(0, 0, 0, 0)[/code] means "derive from the series
+## color supplied by [member TauXYStyle.series_colors]". Any other value
+## becomes a uniform flat fill shared across all series in the overlay.
+## [code]Color(0, 0, 0, 0)[/code] is therefore not a valid explicit fill
+## color.
+##
+## The resolved color has its alpha channel multiplied by
+## [member fill_alpha] before rasterization.
+const DEFAULT_FILL_COLOR: Color = Color(0, 0, 0, 0)
+@export var fill_color: Color = DEFAULT_FILL_COLOR
+
+## Multiplier applied to the alpha channel of the resolved fill color,
+## regardless of whether the color came from [member fill_color] or from
+## [member TauXYStyle.series_colors]. Valid range is [code][0.0, 1.0][/code].
+const DEFAULT_FILL_ALPHA: float = 0.2
+@export var fill_alpha: float = DEFAULT_FILL_ALPHA
+
 
 ####################################################################################################
 # Helpers
@@ -88,22 +106,47 @@ func get_series_dash_px(p_series_index: int) -> int:
 	return max(entry, 0)
 
 
+## Returns the resolved fill color for the given series index.
+##
+## When [member fill_color] is the sentinel [code]Color(0, 0, 0, 0)[/code]
+## the per-series color from [param p_xy_style] is used. Otherwise the flat
+## [member fill_color] wins regardless of the series. In both cases the
+## alpha channel of the returned color is multiplied by [member fill_alpha],
+## clamped to [code][0.0, 1.0][/code].
+func get_series_fill_color(p_series_index: int, p_xy_style: TauXYStyle) -> Color:
+	var base: Color
+	if fill_color == DEFAULT_FILL_COLOR:
+		base = p_xy_style.get_series_color(p_series_index)
+	else:
+		base = fill_color
+	base.a = clampf(base.a * fill_alpha, 0.0, 1.0)
+	return base
+
+
 ####################################################################################################
 # Cascade: theme loading (layer 2)
 ####################################################################################################
 
 ## Loads properties from the Godot theme attached to [param p_control].
 ##
-## All properties on this resource are per-series arrays. For each, a
-## two-level indexed lookup applies at series granularity:
+## The per-series array properties use a two-level indexed lookup at series
+## granularity:
 ##   1. [code]<key>_N[/code] sets the value for series N across all panes.
 ##   2. [code]<key>_N_P[/code] overrides series N in pane P only.
 ##
-## Theme key prefixes:
+## Theme key prefixes for the per-series arrays:
 ##   - [member line_widths_px]:         [code]line_width_px[/code]
 ##   - [member hovered_line_widths_px]: [code]line_hovered_width_px[/code]
 ##   - [member dash_lengths_px]:        [code]line_dash_px[/code]
 ##
+## The scalar fill properties use a non-indexed base key plus a per-pane
+## indexed key that overwrites the base value for the matching pane:
+##   - [member fill_color]: [code]line_fill_color[/code] and
+##     [code]line_fill_color_P[/code].
+##   - [member fill_alpha]: [code]line_fill_alpha_percent[/code] and
+##     [code]line_fill_alpha_percent_P[/code]. Stored as a percentage in
+##     the theme because theme constants are integers.
+##
 ## This method writes every property unconditionally because it is called on
 ## the resolved instance, not on the user-provided resource.
 func load_from_theme(p_control: Control, p_pane_index: int) -> void:
@@ -190,6 +233,23 @@ func load_from_theme(p_control: Control, p_pane_index: int) -> void:
 		dash_lengths_px[pane_dash_index] = max(int(p_control.get_theme_constant(key)), 0)
 		pane_dash_index += 1
 
+	# fill_color: non-indexed key first, then per-pane indexed key overwrites.
+	if p_control.has_theme_color(&"line_fill_color"):
+		fill_color = p_control.get_theme_color(&"line_fill_color")
+	var indexed_fill_color_key := StringName("line_fill_color_%d" % p_pane_index)
+	if p_control.has_theme_color(indexed_fill_color_key):
+		fill_color = p_control.get_theme_color(indexed_fill_color_key)
+
+	# fill_alpha: stored as a percentage in the theme because theme constants
+	# are integers. Non-indexed key first, then per-pane indexed key overwrites.
+	if p_control.has_theme_constant(&"line_fill_alpha_percent"):
+		var alpha_percent := p_control.get_theme_constant(&"line_fill_alpha_percent")
+		fill_alpha = clampf(float(alpha_percent) / 100.0, 0.0, 1.0)
+	var indexed_fill_alpha_key := StringName("line_fill_alpha_percent_%d" % p_pane_index)
+	if p_control.has_theme_constant(indexed_fill_alpha_key):
+		var alpha_percent_p := p_control.get_theme_constant(indexed_fill_alpha_key)
+		fill_alpha = clampf(float(alpha_percent_p) / 100.0, 0.0, 1.0)
+
 
 ####################################################################################################
 # Cascade: user overrides (layer 3)
@@ -214,6 +274,11 @@ func apply_overrides_from(p_user_style: TauLineStyle) -> void:
 	if _is_dash_lengths_overridden(p_user_style.dash_lengths_px):
 		dash_lengths_px = p_user_style.dash_lengths_px.duplicate()
 
+	if p_user_style.fill_color != DEFAULT_FILL_COLOR:
+		fill_color = p_user_style.fill_color
+	if p_user_style.fill_alpha != DEFAULT_FILL_ALPHA:
+		fill_alpha = clampf(p_user_style.fill_alpha, 0.0, 1.0)
+
 
 ####################################################################################################
 # Full cascade resolution
@@ -262,6 +327,10 @@ func is_equal_to(p_other: TauLineStyle) -> bool:
 	for i in range(dash_lengths_px.size()):
 		if dash_lengths_px[i] != p_other.dash_lengths_px[i]:
 			return false
+	if fill_color != p_other.fill_color:
+		return false
+	if fill_alpha != p_other.fill_alpha:
+		return false
 	return true
 
 
diff --git a/addons/tau-plot/plot/xy/line/line_validator.gd b/addons/tau-plot/plot/xy/line/line_validator.gd
index 5488adc..f21e741 100644
--- a/addons/tau-plot/plot/xy/line/line_validator.gd
+++ b/addons/tau-plot/plot/xy/line/line_validator.gd
@@ -49,6 +49,7 @@ class LineValidator extends RefCounted:
 
 		var is_shared_x := (p_dataset.get_mode() == Dataset.Mode.SHARED_X)
 		_validate_line_mode_constraints(p_pane_index, line_config, pane_cfg, p_line_overlay_bindings, is_shared_x, p_result)
+		_validate_fill_constraints(p_pane_index, line_config, pane_cfg, p_line_overlay_bindings, p_result)
 
 
 	####################################################################################################
@@ -91,3 +92,18 @@ class LineValidator extends RefCounted:
 
 			_:
 				p_result.add_error("LineValidator: pane %d: unsupported line mode %d" % [p_pane_index, p_line_config.mode])
+
+
+	static func _validate_fill_constraints(p_pane_index: int, p_line_config: TauLineConfig, p_pane_cfg: TauPaneConfig, p_line_overlay_bindings: Array[TauXYSeriesBinding], p_result: ValidationResult) -> void:
+		if p_line_config.fill_mode != TauLineConfig.FillMode.TO_BASELINE:
+			return
+		if p_line_config.fill_baseline > 0.0:
+			return
+		# A non-positive baseline cannot be mapped on a logarithmic scale,
+		# so the fill is rejected as soon as any line series in this pane
+		# binds to such an axis.
+		for binding in p_line_overlay_bindings:
+			var y_axis_config: TauAxisConfig = p_pane_cfg.get_y_axis_config(binding.y_axis_id)
+			if y_axis_config.scale == TauAxisConfig.Scale.LOGARITHMIC:
+				p_result.add_error("LineValidator: pane %d: fill_mode TO_BASELINE requires fill_baseline > 0 on a logarithmic y axis, got %s" % [p_pane_index, p_line_config.fill_baseline])
+				return
diff --git a/addons/tau-plot/tests/line/area/test_line_fill_color_alpha.gd b/addons/tau-plot/tests/line/area/test_line_fill_color_alpha.gd
new file mode 100644
index 0000000..2d3aa8c
--- /dev/null
+++ b/addons/tau-plot/tests/line/area/test_line_fill_color_alpha.gd
@@ -0,0 +1,285 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+	_setup_test_9()
+	_setup_test_10()
+	_setup_test_11()
+	_setup_test_12()
+	_setup_test_13()
+	_setup_test_14()
+	_setup_test_15()
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 15.0, 10.0])
+	var y_b := PackedFloat64Array([50.0, 40.0, 35.0, 5.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = true
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 10.
+	line_config.style.fill_color = Color(0.5, 0.5, 0.5)
+	line_config.style.fill_alpha = 0.5
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x_a := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 15.0, 10.0])
+	var x_b := PackedFloat64Array([10.5, 11.5, 12.5, 13.5])
+	var y_b := PackedFloat64Array([40.0, 35.0, 5.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 10.
+	line_config.style.fill_color = Color(0.5, 0.5, 0.5)
+	line_config.style.fill_alpha = 0.5
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+func make_shared_x_categorical_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 15.0, 10.0])
+	var y_b := PackedFloat64Array([50.0, 40.0, 35.0, 5.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 10.
+	line_config.style.fill_color = Color(0.5, 0.5, 0.5)
+	line_config.style.fill_alpha = 0.5
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_per_series_x_continuous_plot(%TestPlot2, "[LINEAR] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_categorical_plot(%TestPlot3, "[LINEAR] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_BEFORE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_per_series_x_continuous_plot(%TestPlot5, "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_shared_x_categorical_plot(%TestPlot6, "[STEP_BEFORE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "[STEP_MIDDLE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_per_series_x_continuous_plot(%TestPlot8, "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_categorical_plot(%TestPlot9, "[STEP_MIDDLE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 10
+####################################################################################################
+
+func _setup_test_10() -> void:
+	make_shared_x_continuous_plot(%TestPlot10, "[STEP_AFTER] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 11
+####################################################################################################
+
+func _setup_test_11() -> void:
+	make_per_series_x_continuous_plot(%TestPlot11, "[STEP_AFTER] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 12
+####################################################################################################
+
+func _setup_test_12() -> void:
+	make_shared_x_categorical_plot(%TestPlot12, "[STEP_AFTER] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 13
+####################################################################################################
+
+func _setup_test_13() -> void:
+	make_shared_x_continuous_plot(%TestPlot13, "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+####################################################################################################
+# Test 14
+####################################################################################################
+
+func _setup_test_14() -> void:
+	make_per_series_x_continuous_plot(%TestPlot14, "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+####################################################################################################
+# Test 15
+####################################################################################################
+
+func _setup_test_15() -> void:
+	make_shared_x_categorical_plot(%TestPlot15, "[SMOOTH_MONOTONE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
diff --git a/addons/tau-plot/tests/line/area/test_line_fill_color_alpha.gd.uid b/addons/tau-plot/tests/line/area/test_line_fill_color_alpha.gd.uid
new file mode 100644
index 0000000..fe6ddef
--- /dev/null
+++ b/addons/tau-plot/tests/line/area/test_line_fill_color_alpha.gd.uid
@@ -0,0 +1 @@
+uid://cwl6310pxi58
diff --git a/addons/tau-plot/tests/line/area/test_line_fill_color_alpha.tscn b/addons/tau-plot/tests/line/area/test_line_fill_color_alpha.tscn
new file mode 100644
index 0000000..9338fd0
--- /dev/null
+++ b/addons/tau-plot/tests/line/area/test_line_fill_color_alpha.tscn
@@ -0,0 +1,185 @@
+[gd_scene load_steps=3 format=3 uid="uid://cmwd6dq8si671"]
+
+[ext_resource type="Script" uid="uid://cwl6310pxi58" path="res://addons/tau-plot/tests/line/area/test_line_fill_color_alpha.gd" id="1_3uc4y"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_s8dwp"]
+
+[node name="Lines" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_3uc4y")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Fill to baseline 10 with gray color and alpha = 0.5  for different interpolation modes"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[LINEAR] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[LINEAR] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[LINEAR] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_BEFORE] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_BEFORE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_MIDDLE] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_MIDDLE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot10" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_AFTER] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot11" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot12" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_AFTER] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot13" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot14" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot15" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[SMOOTH_MONOTONE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/area/test_line_fill_linear.gd b/addons/tau-plot/tests/line/area/test_line_fill_linear.gd
new file mode 100644
index 0000000..fb356c8
--- /dev/null
+++ b/addons/tau-plot/tests/line/area/test_line_fill_linear.gd
@@ -0,0 +1,279 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+	_setup_test_9()
+	_setup_test_10()
+	_setup_test_11()
+	_setup_test_12()
+	_setup_test_13()
+	_setup_test_14()
+	_setup_test_15()
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 15.0, 10.0])
+	var y_b := PackedFloat64Array([50.0, 40.0, 35.0, 5.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = true
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 10.
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x_a := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 15.0, 10.0])
+	var x_b := PackedFloat64Array([10.5, 11.5, 12.5, 13.5])
+	var y_b := PackedFloat64Array([40.0, 35.0, 5.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 10.
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+func make_shared_x_categorical_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([10.0, 20.0, 50.0, 15.0, 10.0])
+	var y_b := PackedFloat64Array([50.0, 40.0, 35.0, 5.0, 20.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LINEAR
+	y_axis.tick_count_preferred = 10
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 10.
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_per_series_x_continuous_plot(%TestPlot2, "[LINEAR] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_categorical_plot(%TestPlot3, "[LINEAR] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_BEFORE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_per_series_x_continuous_plot(%TestPlot5, "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_shared_x_categorical_plot(%TestPlot6, "[STEP_BEFORE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "[STEP_MIDDLE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_per_series_x_continuous_plot(%TestPlot8, "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_categorical_plot(%TestPlot9, "[STEP_MIDDLE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 10
+####################################################################################################
+
+func _setup_test_10() -> void:
+	make_shared_x_continuous_plot(%TestPlot10, "[STEP_AFTER] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 11
+####################################################################################################
+
+func _setup_test_11() -> void:
+	make_per_series_x_continuous_plot(%TestPlot11, "[STEP_AFTER] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 12
+####################################################################################################
+
+func _setup_test_12() -> void:
+	make_shared_x_categorical_plot(%TestPlot12, "[STEP_AFTER] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 13
+####################################################################################################
+
+func _setup_test_13() -> void:
+	make_shared_x_continuous_plot(%TestPlot13, "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+####################################################################################################
+# Test 14
+####################################################################################################
+
+func _setup_test_14() -> void:
+	make_per_series_x_continuous_plot(%TestPlot14, "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+####################################################################################################
+# Test 15
+####################################################################################################
+
+func _setup_test_15() -> void:
+	make_shared_x_categorical_plot(%TestPlot15, "[SMOOTH_MONOTONE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
diff --git a/addons/tau-plot/tests/line/area/test_line_fill_linear.gd.uid b/addons/tau-plot/tests/line/area/test_line_fill_linear.gd.uid
new file mode 100644
index 0000000..f3f7280
--- /dev/null
+++ b/addons/tau-plot/tests/line/area/test_line_fill_linear.gd.uid
@@ -0,0 +1 @@
+uid://buxrc2ogu8cne
diff --git a/addons/tau-plot/tests/line/area/test_line_fill_linear.tscn b/addons/tau-plot/tests/line/area/test_line_fill_linear.tscn
new file mode 100644
index 0000000..2b4eb0d
--- /dev/null
+++ b/addons/tau-plot/tests/line/area/test_line_fill_linear.tscn
@@ -0,0 +1,185 @@
+[gd_scene load_steps=3 format=3 uid="uid://cpswbt2gwdeki"]
+
+[ext_resource type="Script" uid="uid://buxrc2ogu8cne" path="res://addons/tau-plot/tests/line/area/test_line_fill_linear.gd" id="1_pel2m"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_fkav2"]
+
+[node name="Lines" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_pel2m")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Fill to baseline 10 with different interpolation modes (linear scale)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[LINEAR] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[LINEAR] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[LINEAR] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[STEP_BEFORE] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[STEP_BEFORE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[STEP_MIDDLE] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[STEP_MIDDLE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot10" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[STEP_AFTER] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot11" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot12" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[STEP_AFTER] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot13" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot14" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot15" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_fkav2")
+title = "[SMOOTH_MONOTONE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/area/test_line_fill_logarithmic.gd b/addons/tau-plot/tests/line/area/test_line_fill_logarithmic.gd
new file mode 100644
index 0000000..7abf6c4
--- /dev/null
+++ b/addons/tau-plot/tests/line/area/test_line_fill_logarithmic.gd
@@ -0,0 +1,276 @@
+@tool
+extends Control
+
+func _ready() -> void:
+	_setup_test_1()
+	_setup_test_2()
+	_setup_test_3()
+	_setup_test_4()
+	_setup_test_5()
+	_setup_test_6()
+	_setup_test_7()
+	_setup_test_8()
+	_setup_test_9()
+	_setup_test_10()
+	_setup_test_11()
+	_setup_test_12()
+	_setup_test_13()
+	_setup_test_14()
+	_setup_test_15()
+
+####################################################################################################
+# Helpers
+####################################################################################################
+
+func make_shared_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([100.0, 400.0, 2500.0, 225.0, 100.0])
+	var y_b := PackedFloat64Array([2500.0, 1600.0, 1225.0, 25.0, 400.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_continuous(series_names, x, [y_a, y_b])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = true
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 100.
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+func make_per_series_x_continuous_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x_a := PackedFloat64Array([10.0, 11.0, 12.0, 13.0, 14.0])
+	var y_a := PackedFloat64Array([100.0, 400.0, 2500.0, 225.0, 100.0])
+	var x_b := PackedFloat64Array([10.5, 11.5, 12.5, 13.5])
+	var y_b := PackedFloat64Array([1600.0, 1225.0, 25.0, 400.0])
+
+	var dataset := TauPlot.Dataset.make_per_series_x_continuous(series_names, [x_a, x_b], [y_a, y_b])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CONTINUOUS
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 100.
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+func make_shared_x_categorical_plot(p_plot: TauPlot, p_title: String, p_interpolation: TauLineConfig.InterpolationMode) -> void:
+	var series_names := PackedStringArray(["Series A", "Series B"])
+	var x := PackedStringArray(["One", "Two", "Three", "Four", "Five"])
+	var y_a := PackedFloat64Array([100.0, 400.0, 2500.0, 225.0, 100.0])
+	var y_b := PackedFloat64Array([2500.0, 1600.0, 1225.0, 25.0, 400.0])
+
+	var dataset := TauPlot.Dataset.make_shared_x_categorical(series_names, x, [y_a, y_b])
+
+	p_plot.title = p_title
+	p_plot.legend_enabled = false
+
+	var x_axis := TauAxisConfig.new()
+	x_axis.type = TauAxisConfig.Type.CATEGORICAL
+	x_axis.scale = TauAxisConfig.Scale.LINEAR
+
+	var y_axis := TauAxisConfig.new()
+	y_axis.type = TauAxisConfig.Type.CONTINUOUS
+	y_axis.scale = TauAxisConfig.Scale.LOGARITHMIC
+	y_axis.overlap_strategy = TauAxisConfig.OverlapStrategy.NONE
+
+	var line_config := TauLineConfig.new()
+	line_config.mode = TauLineConfig.LineMode.INDEPENDENT
+	line_config.interpolation_mode = p_interpolation
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 100.
+
+	var pane := TauPaneConfig.new()
+	pane.y_left_axis = y_axis
+	pane.overlays = [line_config]
+
+	var config := TauXYConfig.new()
+	config.x_axis = x_axis
+	config.panes = [pane]
+
+	var sb_a := TauXYSeriesBinding.new()
+	sb_a.series_id = dataset.get_series_id_by_index(0)
+	sb_a.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_a.y_axis_id = TauPlot.AxisId.LEFT
+
+	var sb_b := TauXYSeriesBinding.new()
+	sb_b.series_id = dataset.get_series_id_by_index(1)
+	sb_b.overlay_type = TauXYSeriesBinding.PaneOverlayType.LINE
+	sb_b.y_axis_id = TauPlot.AxisId.LEFT
+
+	var bindings: Array[TauXYSeriesBinding] = [sb_a, sb_b]
+
+	p_plot.plot_xy(dataset, config, bindings)
+
+
+####################################################################################################
+# Test 1
+####################################################################################################
+
+func _setup_test_1() -> void:
+	make_shared_x_continuous_plot(%TestPlot1, "[LINEAR] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 2
+####################################################################################################
+
+func _setup_test_2() -> void:
+	make_per_series_x_continuous_plot(%TestPlot2, "[LINEAR] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 3
+####################################################################################################
+
+func _setup_test_3() -> void:
+	make_shared_x_categorical_plot(%TestPlot3, "[LINEAR] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.LINEAR)
+
+####################################################################################################
+# Test 4
+####################################################################################################
+
+func _setup_test_4() -> void:
+	make_shared_x_continuous_plot(%TestPlot4, "[STEP_BEFORE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 5
+####################################################################################################
+
+func _setup_test_5() -> void:
+	make_per_series_x_continuous_plot(%TestPlot5, "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 6
+####################################################################################################
+
+func _setup_test_6() -> void:
+	make_shared_x_categorical_plot(%TestPlot6, "[STEP_BEFORE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_BEFORE)
+
+####################################################################################################
+# Test 7
+####################################################################################################
+
+func _setup_test_7() -> void:
+	make_shared_x_continuous_plot(%TestPlot7, "[STEP_MIDDLE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 8
+####################################################################################################
+
+func _setup_test_8() -> void:
+	make_per_series_x_continuous_plot(%TestPlot8, "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 9
+####################################################################################################
+
+func _setup_test_9() -> void:
+	make_shared_x_categorical_plot(%TestPlot9, "[STEP_MIDDLE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_MIDDLE)
+
+####################################################################################################
+# Test 10
+####################################################################################################
+
+func _setup_test_10() -> void:
+	make_shared_x_continuous_plot(%TestPlot10, "[STEP_AFTER] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 11
+####################################################################################################
+
+func _setup_test_11() -> void:
+	make_per_series_x_continuous_plot(%TestPlot11, "[STEP_AFTER] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 12
+####################################################################################################
+
+func _setup_test_12() -> void:
+	make_shared_x_categorical_plot(%TestPlot12, "[STEP_AFTER] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.STEP_AFTER)
+
+####################################################################################################
+# Test 13
+####################################################################################################
+
+func _setup_test_13() -> void:
+	make_shared_x_continuous_plot(%TestPlot13, "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+####################################################################################################
+# Test 14
+####################################################################################################
+
+func _setup_test_14() -> void:
+	make_per_series_x_continuous_plot(%TestPlot14, "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
+
+####################################################################################################
+# Test 15
+####################################################################################################
+
+func _setup_test_15() -> void:
+	make_shared_x_categorical_plot(%TestPlot15, "[SMOOTH_MONOTONE] SHARED_X + CATEGORICAL", TauLineConfig.InterpolationMode.SMOOTH_MONOTONE)
diff --git a/addons/tau-plot/tests/line/area/test_line_fill_logarithmic.gd.uid b/addons/tau-plot/tests/line/area/test_line_fill_logarithmic.gd.uid
new file mode 100644
index 0000000..e1d2e0a
--- /dev/null
+++ b/addons/tau-plot/tests/line/area/test_line_fill_logarithmic.gd.uid
@@ -0,0 +1 @@
+uid://gmom2vph7l32
diff --git a/addons/tau-plot/tests/line/area/test_line_fill_logarithmic.tscn b/addons/tau-plot/tests/line/area/test_line_fill_logarithmic.tscn
new file mode 100644
index 0000000..87f0b64
--- /dev/null
+++ b/addons/tau-plot/tests/line/area/test_line_fill_logarithmic.tscn
@@ -0,0 +1,185 @@
+[gd_scene load_steps=3 format=3 uid="uid://bdxoyoq0ffkui"]
+
+[ext_resource type="Script" uid="uid://gmom2vph7l32" path="res://addons/tau-plot/tests/line/area/test_line_fill_logarithmic.gd" id="1_241pk"]
+[ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_s8dwp"]
+
+[node name="Lines" type="VBoxContainer"]
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_241pk")
+
+[node name="Title" type="Label" parent="."]
+layout_mode = 2
+theme_override_font_sizes/font_size = 32
+text = "Fill to baseline 100 with different interpolation modes (log scale)"
+horizontal_alignment = 1
+
+[node name="GridContainer" type="GridContainer" parent="."]
+layout_mode = 2
+size_flags_vertical = 3
+theme_override_constants/h_separation = 0
+theme_override_constants/v_separation = 0
+columns = 3
+
+[node name="TestPlot1" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[LINEAR] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[LINEAR] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[LINEAR] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_BEFORE] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_BEFORE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_BEFORE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_MIDDLE] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_MIDDLE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot9" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_MIDDLE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot10" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_AFTER] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot11" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_AFTER] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot12" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[STEP_AFTER] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot13" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[SMOOTH_MONOTONE] SHARED_X + CONTINUOUS"
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot14" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[SMOOTH_MONOTONE] PER_SERIES_X + CONTINUOUS"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
+
+[node name="TestPlot15" type="PanelContainer" parent="GridContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_type_variation = &"TauPlot"
+script = ExtResource("2_s8dwp")
+title = "[SMOOTH_MONOTONE] SHARED_X + CATEGORICAL"
+legend_enabled = false
+metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/dash/test_line_dash.tscn b/addons/tau-plot/tests/line/dash/test_line_dash.tscn
index d7b61ae..d8464bb 100644
--- a/addons/tau-plot/tests/line/dash/test_line_dash.tscn
+++ b/addons/tau-plot/tests/line/dash/test_line_dash.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://ccebd3cs615t7" path="res://addons/tau-plot/tests/line/dash/test_line_dash.gd" id="1_4q4uh"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_mp1bp"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn
index 8db02d7..3e93800 100644
--- a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://dagnw8rnu7ils" path="res://addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_linear.gd" id="1_ahkji"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_nry5o"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
index 7557394..4623344 100644
--- a/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
+++ b/addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://bsivl5p06vdek" path="res://addons/tau-plot/tests/line/interpolation_mode/test_line_interpolation_logarithmic.gd" id="1_g1sf8"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_u5as0"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.tscn b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.tscn
index 911e9f1..1f256ee 100644
--- a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.tscn
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://vi4vdovvscly" path="res://addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_alpha.gd" id="1_lv2ey"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_touct"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.tscn b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.tscn
index c77ef9a..9cfb98d 100644
--- a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.tscn
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://5dh41vpm1xd3" path="res://addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_dash_color.gd" id="1_yv5ay"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_le50r"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.tscn b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.tscn
index 45a5473..4427421 100644
--- a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.tscn
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://vro08bntv7uo" path="res://addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_alpha.gd" id="1_u76at"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_hy82u"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.tscn b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.tscn
index 1d39731..e2c244e 100644
--- a/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.tscn
+++ b/addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://c78fi08wv7vqd" path="res://addons/tau-plot/tests/line/line_attributes/test_line_visual_attributes_solid_color.gd" id="1_7vjol"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_lc0kd"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.tscn b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.tscn
index 7dc3e02..b768b86 100644
--- a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.tscn
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://d1ehkjmoa0dhx" path="res://addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_alpha.gd" id="1_w8xoc"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_wvy6q"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.tscn b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.tscn
index 41f03e1..b8c603d 100644
--- a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.tscn
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://tgw2e12ovgd" path="res://addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_dash_color.gd" id="1_mx55d"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_0c0l8"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.tscn b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.tscn
index 4363503..5ab41cc 100644
--- a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.tscn
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://byunb5b3q5f0n" path="res://addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_alpha.gd" id="1_8ct1l"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_ronnj"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.tscn b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.tscn
index 2a93ff8..588c974 100644
--- a/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.tscn
+++ b/addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://bnuv0vxxw14ea" path="res://addons/tau-plot/tests/line/line_callbacks/test_line_visual_callbacks_solid_color.gd" id="1_lev7j"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_xbeyi"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/log_scale/test_line_logarithmic.tscn b/addons/tau-plot/tests/line/log_scale/test_line_logarithmic.tscn
index 280d768..15a14a6 100644
--- a/addons/tau-plot/tests/line/log_scale/test_line_logarithmic.tscn
+++ b/addons/tau-plot/tests/line/log_scale/test_line_logarithmic.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://b5nqjwb6flndn" path="res://addons/tau-plot/tests/line/log_scale/test_line_logarithmic.gd" id="1_k4moc"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_erpj8"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd
index ca687e2..c27744c 100644
--- a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd
@@ -37,6 +37,8 @@ func _setup_test_1() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -88,6 +90,8 @@ func _setup_test_2() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -138,6 +142,8 @@ func _setup_test_3() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -189,6 +195,8 @@ func _setup_test_4() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -239,6 +247,8 @@ func _setup_test_5() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -290,6 +300,8 @@ func _setup_test_6() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -340,6 +352,8 @@ func _setup_test_7() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 1.
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -391,6 +405,8 @@ func _setup_test_8() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.BRIDGE
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 1.
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.tscn b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.tscn
index bc0c825..0cd12ca 100644
--- a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.tscn
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://cym0c8dl4swxu" path="res://addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_bridge.gd" id="1_156gm"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_v7edd"]
 
-[node name="Scatters" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
@@ -31,7 +31,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_v7edd")
-title = "[SHARED_X] 2nd and 4th x values are invalid"
+title = "[SHARED_X] 3rd and 4th x values are invalid"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot2" type="PanelContainer" parent="GridContainer"]
@@ -41,7 +41,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_v7edd")
-title = "[PER_SERIES_X] 2nd and 4th x values are invalid for series A"
+title = "[PER_SERIES_X] 3rd and 4th x values are invalid for series A"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot3" type="PanelContainer" parent="GridContainer"]
@@ -51,7 +51,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_v7edd")
-title = "[SHARED_X] 2nd and 4th y values are invalid for series A"
+title = "[SHARED_X] 3rd and 4th y values are invalid for series A"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
@@ -61,7 +61,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_v7edd")
-title = "[PER_SERIES_X] 2nd and 4th y values are invalid for series A"
+title = "[PER_SERIES_X] 3rd and 4th y values are invalid for series A"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot5" type="PanelContainer" parent="GridContainer"]
@@ -71,7 +71,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_v7edd")
-title = "[LOG][SHARED_X] 2nd and 4th x values are negative"
+title = "[LOG][SHARED_X] 3rd and 4th x values are invalid"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot6" type="PanelContainer" parent="GridContainer"]
@@ -81,7 +81,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_v7edd")
-title = "[LOG][PER_SERIES_X] 2nd and 4th x values are negative for series A"
+title = "[LOG][PER_SERIES_X] 3rd and 4th x values are invalid for series A"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot7" type="PanelContainer" parent="GridContainer"]
@@ -91,7 +91,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_v7edd")
-title = "[LOG][SHARED_X] 2nd and 4th y values are negative for series A"
+title = "[LOG][SHARED_X] 3rd and 4th y values are invalid for series A"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot8" type="PanelContainer" parent="GridContainer"]
@@ -101,5 +101,5 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_v7edd")
-title = "[LOG][PER_SERIES_X] 2nd and 4th y values are negative for series A"
+title = "[LOG][PER_SERIES_X] 3rd and 4th y values are invalid for series A"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd
index 1537c8a..af2f4b4 100644
--- a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd
@@ -37,6 +37,8 @@ func _setup_test_1() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -88,6 +90,8 @@ func _setup_test_2() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -138,6 +142,8 @@ func _setup_test_3() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -189,6 +195,8 @@ func _setup_test_4() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -239,6 +247,8 @@ func _setup_test_5() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -290,6 +300,8 @@ func _setup_test_6() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 0.
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
@@ -340,6 +352,8 @@ func _setup_test_7() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 1.
 
 	var pane_config := TauPaneConfig.new()
 	pane_config.y_left_axis = y_axis
@@ -391,6 +405,8 @@ func _setup_test_8() -> void:
 
 	var line_config := TauLineConfig.new()
 	line_config.gap_policy = TauLineConfig.GapPolicy.SKIP
+	line_config.fill_mode = TauLineConfig.FillMode.TO_BASELINE
+	line_config.fill_baseline = 1.
 
 	var pane := TauPaneConfig.new()
 	pane.y_left_axis = y_axis
diff --git a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn
index 9e7f315..7e1e985 100644
--- a/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn
+++ b/addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://bokuk27l1c8du" path="res://addons/tau-plot/tests/line/nan_or_inf/test_line_nan_inf_skip.gd" id="1_e73yd"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_5c7d4"]
 
-[node name="Scatters" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.tscn b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.tscn
index e6c96b9..8a48488 100644
--- a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.tscn
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://t5fdpmq6toqn" path="res://addons/tau-plot/tests/line/stacked/test_line_stacked_negative_fraction.gd" id="1_kstpx"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_71bbx"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.tscn b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.tscn
index 34ff9ea..44a7b54 100644
--- a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.tscn
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://gq3klvlipxkr" path="res://addons/tau-plot/tests/line/stacked/test_line_stacked_negative_none.gd" id="1_t3a0d"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_q7rrf"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.tscn b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.tscn
index bd41d1e..a4e6b3e 100644
--- a/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.tscn
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://bpbp8mimvrtki" path="res://addons/tau-plot/tests/line/stacked/test_line_stacked_negative_percent.gd" id="1_os7bv"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_tcxo6"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
@@ -51,6 +51,7 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_tcxo6")
+title = "[CONTINUOUS] with stacked_negative_policy = SIGNED_SUM"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
 
 [node name="TestPlot4" type="PanelContainer" parent="GridContainer"]
@@ -80,4 +81,5 @@ size_flags_horizontal = 3
 size_flags_vertical = 3
 theme_type_variation = &"TauPlot"
 script = ExtResource("2_tcxo6")
+title = "[CATEGORICAL] with stacked_negative_policy = SIGNED_SUM"
 metadata/_custom_type_script = "uid://dnhvsf2wip771"
diff --git a/addons/tau-plot/tests/line/stacked/test_line_stacking_order.tscn b/addons/tau-plot/tests/line/stacked/test_line_stacking_order.tscn
index 47a2ab1..bab0427 100644
--- a/addons/tau-plot/tests/line/stacked/test_line_stacking_order.tscn
+++ b/addons/tau-plot/tests/line/stacked/test_line_stacking_order.tscn
@@ -3,7 +3,7 @@
 [ext_resource type="Script" uid="uid://cc44m4dwx745i" path="res://addons/tau-plot/tests/line/stacked/test_line_stacking_order.gd" id="1_if76y"]
 [ext_resource type="Script" uid="uid://dnhvsf2wip771" path="res://addons/tau-plot/plot/plot.gd" id="2_e36ro"]
 
-[node name="Bars" type="VBoxContainer"]
+[node name="Lines" type="VBoxContainer"]
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0