Support 2 point conical gradient

This is a straight port from Skia

Author: wmedrano

CHANGELOG.md

@@ -5,6 +5,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
+### Added
+- 2-point conical gradient support (`ConicalGradient`).
+
 
 ## [0.11.4] - 2024-02-04
 ### Fixed

path/src/scalar.rs

@@ -24,6 +24,7 @@ pub trait Scalar {
     fn invert(self) -> Self;
     fn bound(self, min: Self, max: Self) -> Self;
     fn is_nearly_equal(self, other: Self) -> bool;
+    fn is_nearly_equal_within_tolerance(self, other: Self, tolerance: Self) -> bool;
     fn is_nearly_zero(self) -> bool;
     fn is_nearly_zero_within_tolerance(self, tolerance: Self) -> bool;
     fn almost_dequal_ulps(self, other: Self) -> bool;
@@ -56,6 +57,10 @@ impl Scalar for f32 {
         (self - other).abs() <= SCALAR_NEARLY_ZERO
     }
 
+    fn is_nearly_equal_within_tolerance(self, other: Self, tolerance: Self) -> bool {
+        (self - other).abs() <= tolerance
+    }
+
     fn is_nearly_zero(self) -> bool {
         self.is_nearly_zero_within_tolerance(SCALAR_NEARLY_ZERO)
     }

src/lib.rs

@@ -63,7 +63,7 @@ pub use mask::{Mask, MaskType};
 pub use painter::{FillRule, Paint};
 pub use pixmap::{Pixmap, PixmapMut, PixmapRef, BYTES_PER_PIXEL};
 pub use shaders::{FilterQuality, GradientStop, PixmapPaint, SpreadMode};
-pub use shaders::{LinearGradient, Pattern, RadialGradient, Shader};
+pub use shaders::{LinearGradient, Pattern, RadialGradient, ConicalGradient, Shader};
 
 pub use tiny_skia_path::{IntRect, IntSize, NonZeroRect, Point, Rect, Size, Transform};
 pub use tiny_skia_path::{LineCap, LineJoin, Stroke, StrokeDash};

src/pipeline/highp.rs

@@ -116,9 +116,16 @@ pub const STAGES: &[StageFn; super::STAGES_COUNT] = &[
     xy_to_radius,
     xy_to_2pt_conical_focal_on_circle,
     xy_to_2pt_conical_well_behaved,
+    xy_to_2pt_conical_smaller,
     xy_to_2pt_conical_greater,
+    xy_to_2pt_conical_strip,
+    mask_2pt_conical_nan,
     mask_2pt_conical_degenerates,
     apply_vector_mask,
+    alter_2pt_conical_compensate_focal,
+    alter_2pt_conical_unswap,
+    negate_x,
+    apply_concentric_scale_bias,
     gamma_expand_2,
     gamma_expand_dst_2,
     gamma_compress_2,
@@ -1017,16 +1024,34 @@ fn xy_to_2pt_conical_greater(p: &mut Pipeline) {
     p.next_stage();
 }
 
-fn mask_2pt_conical_degenerates(p: &mut Pipeline) {
-    let ctx = &mut p.ctx.two_point_conical_gradient;
+// From: https://source.chromium.org/chromium/chromium/src/+/main:third_party/skia/src/opts/SkRasterPipeline_opts.h;l=3625;drc=d5c02fd369596fb4a6fa563f5506ff71ff7299ed
+fn xy_to_2pt_conical_smaller(p: &mut Pipeline) {
+    let ctx = &p.ctx.two_point_conical_gradient;
 
-    let t = p.r;
-    let is_degenerate = t.cmp_le(f32x8::default()) | t.cmp_ne(t);
-    p.r = is_degenerate.blend(f32x8::default(), t);
+    let x = p.r;
+    let y = p.g;
+    p.r = -(x * x - y * y).sqrt() - x * f32x8::splat(ctx.p0);
+
+    p.next_stage();
+}
+
+// From: https://source.chromium.org/chromium/chromium/src/+/main:third_party/skia/src/opts/SkRasterPipeline_opts.h;l=3605;drc=d5c02fd369596fb4a6fa563f5506ff71ff7299ed
+fn xy_to_2pt_conical_strip(p: &mut Pipeline) {
+    let ctx = &p.ctx.two_point_conical_gradient;
+
+    let x = p.r;
+    let y = p.g;
+    p.r = x + (f32x8::splat(ctx.p0) - y * y).sqrt();
+
+    p.next_stage();
+}
 
+
+#[inline]
+fn mask_2pt_conical_from_degenerate(is_degenerate: f32x8) -> u32x8 {
     let is_not_degenerate = !is_degenerate.to_u32x8_bitcast();
     let is_not_degenerate: [u32; 8] = bytemuck::cast(is_not_degenerate);
-    ctx.mask = bytemuck::cast([
+    bytemuck::cast([
         if is_not_degenerate[0] != 0 { !0 } else { 0 },
         if is_not_degenerate[1] != 0 { !0 } else { 0 },
         if is_not_degenerate[2] != 0 { !0 } else { 0 },
@@ -1035,7 +1060,29 @@ fn mask_2pt_conical_degenerates(p: &mut Pipeline) {
         if is_not_degenerate[5] != 0 { !0 } else { 0 },
         if is_not_degenerate[6] != 0 { !0 } else { 0 },
         if is_not_degenerate[7] != 0 { !0 } else { 0 },
-    ]);
+    ])
+}
+
+
+// From: https://source.chromium.org/chromium/chromium/src/+/main:third_party/skia/src/opts/SkRasterPipeline_opts.h;l=3641;drc=d5c02fd369596fb4a6fa563f5506ff71ff7299ed
+fn mask_2pt_conical_nan(p: &mut Pipeline) {
+    let ctx = &mut p.ctx.two_point_conical_gradient;
+
+    let t = p.r;
+    let is_degenerate = t.cmp_ne(t);
+    p.r = is_degenerate.blend(f32x8::default(), t);
+    ctx.mask = mask_2pt_conical_from_degenerate(is_degenerate);
+
+    p.next_stage();
+}
+
+fn mask_2pt_conical_degenerates(p: &mut Pipeline) {
+    let ctx = &mut p.ctx.two_point_conical_gradient;
+
+    let t = p.r;
+    let is_degenerate = t.cmp_le(f32x8::default()) | t.cmp_ne(t);
+    p.r = is_degenerate.blend(f32x8::default(), t);
+    ctx.mask = mask_2pt_conical_from_degenerate(is_degenerate);
 
     p.next_stage();
 }
@@ -1051,6 +1098,40 @@ fn apply_vector_mask(p: &mut Pipeline) {
     p.next_stage();
 }
 
+// From: https://source.chromium.org/chromium/chromium/src/+/main:third_party/skia/src/opts/SkRasterPipeline_opts.h;l=3630;drc=d5c02fd369596fb4a6fa563f5506ff71ff7299ed
+fn alter_2pt_conical_compensate_focal(p: &mut Pipeline) {
+    let ctx = &p.ctx.two_point_conical_gradient;
+
+    p.r = p.r + f32x8::splat(ctx.p1);
+
+    p.next_stage();
+}
+
+// From: https://source.chromium.org/chromium/chromium/src/+/main:third_party/skia/src/opts/SkRasterPipeline_opts.h;l=3636;drc=d5c02fd369596fb4a6fa563f5506ff71ff7299ed
+fn alter_2pt_conical_unswap(p: &mut Pipeline) {
+    p.r = f32x8::splat(1.0) - p.r;
+
+    p.next_stage();
+}
+
+// From: https://source.chromium.org/chromium/chromium/src/+/main:third_party/skia/src/opts/SkRasterPipeline_opts.h;l=3603;drc=d5c02fd369596fb4a6fa563f5506ff71ff7299ed
+fn negate_x(p: &mut Pipeline) {
+    p.r = -p.r;
+
+    p.next_stage();
+}
+
+// Applies the matrix operation from: https://source.chromium.org/chromium/chromium/src/+/main:third_party/skia/src/shaders/gradients/SkConicalGradient.cpp;l=206;drc=075316994c97ee86961b369bb2bff246aaa9d6c4
+fn apply_concentric_scale_bias(p: &mut Pipeline) {
+    let ctx = &p.ctx.two_point_conical_gradient;
+
+    // Apply t = t * scale + bias for concentric gradients
+    let x = p.r;
+    p.r = x * f32x8::splat(ctx.p0) + f32x8::splat(ctx.p1);
+
+    p.next_stage();
+}
+
 fn gamma_expand_2(p: &mut Pipeline) {
     p.r = p.r * p.r;
     p.g = p.g * p.g;

src/pipeline/lowp.rs

@@ -129,9 +129,16 @@ pub const STAGES: &[StageFn; super::STAGES_COUNT] = &[
     xy_to_radius,
     null_fn, // XYTo2PtConicalFocalOnCircle
     null_fn, // XYTo2PtConicalWellBehaved
+    null_fn, // XYTo2PtConicalSmaller
     null_fn, // XYTo2PtConicalGreater
+    null_fn, // XYTo2PtConicalStrip
+    null_fn, // Mask2PtConicalNan
     null_fn, // Mask2PtConicalDegenerates
     null_fn, // ApplyVectorMask
+    null_fn, // Alter2PtConicalCompensateFocal
+    null_fn, // Alter2PtConicalUnswap
+    null_fn, // NegateX
+    null_fn, // ApplyConcentricScaleBias
     null_fn, // GammaExpand2
     null_fn, // GammaExpandDestination2
     null_fn, // GammaCompress2

src/pipeline/mod.rs

@@ -127,9 +127,16 @@ pub enum Stage {
     XYToRadius,
     XYTo2PtConicalFocalOnCircle,
     XYTo2PtConicalWellBehaved,
+    XYTo2PtConicalSmaller,
     XYTo2PtConicalGreater,
+    XYTo2PtConicalStrip,
+    Mask2PtConicalNan,
     Mask2PtConicalDegenerates,
     ApplyVectorMask,
+    Alter2PtConicalCompensateFocal,
+    Alter2PtConicalUnswap,
+    NegateX,
+    ApplyConcentricScaleBias,
     GammaExpand2,
     GammaExpandDestination2,
     GammaCompress2,
@@ -327,6 +334,7 @@ pub struct TwoPointConicalGradientCtx {
     // This context is used only in highp, where we use Tx4.
     pub mask: u32x8,
     pub p0: f32,
+    pub p1: f32,
 }
 
 #[derive(Copy, Clone, Default, Debug)]