Phase 4: layout writing modes#32
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Phase 4 ships WritingMode + WritingModeResolved with a new pre-SyncStyles inheritance pipeline step. LogicalBoxModel + LogicalInset are non-component author-ergonomic builders translating logical -> physical at construct time. Direction::Rtl wires through taffy::Style.direction; sideways-* fall back to vertical-rl/lr with warn-once. ContainingBlock cache deferred to Phase 6 (anchor positioning) where it has a consumer. Plan tagged [active]; flips to [landed] post-merge.
Three reviewer agents surfaced 5 real BLOCKERs; this revision addresses: 1. Single-level inheritance — replaced with memoized ancestor walk that honors spec § 2.2 'nearest ancestor's' across arbitrary depth. 2. Changed<WritingModeResolved> cascade — system now reads existing resolved value and only inserts when changed, preserving Phase 1's O(0) steady-state contract. 3. Pipeline order test rewrite — explicit 9-tracker / 9-label diff instead of glossing over the test's actual structure. 4. Task 4 signature mismatch — LogicalEdges::to_edges takes (WritingModeKind, Direction) tuple form. Test snippets aligned. 5. Task 2 dead_code — added #[allow(dead_code)] on WritingModeResolved::from_writing_mode pending Task 3 consumer. Plus: Decision item #13 documents the spec § 4.2 'dynamic re-translation pass' deferral to v1.x; coverage-map row added to call out the deferral; pipeline.rs '8-step' doc-comment widening called out in Task 3.
Adds WritingModeKind, Direction, TextOrientation, UnicodeBidi. Sideways variants reach a warn-once gate in Phase 4 Task 5; TextOrientation and UnicodeBidi are stored only (consumed by buiy-text-rendering-design and buiy-i18n-design respectively, not layout).
WritingMode (author-set, will join Style Bundle in Task 6) carries the full CSS writing-mode + direction + text-orientation + unicode-bidi surface. WritingModeResolved (private cache, synced by Task 3's inheritance pass) carries the inherited effective value used by translate.rs in Task 5. #[allow(dead_code)] on WritingModeResolved::from_writing_mode pending Task 3's consumer; clippy -D warnings would otherwise reject the unused pub(crate) helper.
New BuiyLayoutStep::WritingModeInherit set runs between RemovedNodesGc and SyncStyles, populating WritingModeResolved by walking ancestors via ChildOf. The walk is memoized in a per-frame HashMap so each entity's effective WritingMode is resolved at most once even when many descendants share an ancestor (O(N) total, not O(N x depth)). The inherit_writing_mode system reads the entity's current WritingModeResolved and only commands.insert(...) when the new value differs. This idempotence is load-bearing: Task 5 widens sync_styles's trigger filter to depend on Changed<WritingModeResolved>, and an unconditional re-insert every frame would void Phase 1's O(0) steady-state contract. Drops the #[allow(dead_code)] on WritingModeResolved::from_writing_mode now that the inheritance system consumes it. Pipeline test widens from 8 to 9 expected steps; trackers re-labeled by enum order (gc, wmi, sync, cq_activate, taffy, cq_flip, cq_rerun, post_taffy, write) so the assertion is visually unambiguous. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
…ilders Non-component, non-Bundle author-ergonomic structs. Each carries logical (writing-mode-aware) edges or dimensions and emits the corresponding physical type via .to_edges / .to_box_model / .to_inset. The 6-row mapping table from the spec is exercised by the new unit tests; vertical-rl / vertical-lr swap inline <-> block onto height <-> width. LogicalEdges::to_edges takes (mode, direction) directly to keep the types.rs -> components.rs dependency one-way; style.rs callers (LogicalBoxModel, LogicalInset) hold a &WritingMode and forward wm.mode, wm.direction. LogicalInset duplicates the 6-row mapping because Inset uses Sizing (not Length), so it can't reuse LogicalEdges::to_edges. Sideways modes are silently normalized to their non-sideways vertical equivalents (the warn-once gate lands in Task 5). LogicalEdges + LogicalInset take self by value to satisfy clippy::wrong_self_convention (both derive Copy); LogicalBoxModel takes &self because it's intentionally non-Copy per the plan. The three structs and their to_* methods carry #[allow(dead_code)] for the lib build until Task 6 wires Style fluent setters and Task 7 re-exports them.
Atomic: extends StyleView with writing_mode_resolved; populates taffy::Style.direction from WritingModeResolved.direction; sideways-* modes hit a warn-once gate naming buiy-text-rendering-design as the future owner. sync_styles' Or filter widens with Changed<WritingMode> and Changed<WritingModeResolved>. Phase 2 invariant intact: Changed<ScrollOffset> / Changed<ScrollSnapItem> remain excluded. Note: this is one commit because StyleView is the bridge between translate.rs and systems.rs - splitting would break the lib build between commits. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
7 new setters: .writing_mode, .writing_mode_kind, .direction, .ltr, .rtl, .text_orientation, .unicode_bidi. WritingModeResolved stays out of the Bundle (private cache, populated by inherit_writing_mode).
WritingMode + WritingModeResolved registered for reflection; new value types (WritingModeKind, Direction, TextOrientation, UnicodeBidi, LogicalEdges) and builders (LogicalBoxModel, LogicalInset) re-exported from buiy_core and the buiy facade alongside Phases 1-3 surface. Drops the dead_code allows on LogicalBoxModel / LogicalInset / LogicalEdges and their methods now that the public re-export wires them in.
Integration tests pin: rtl flips flex-row child order; vertical-rl
swaps inline/block dimensions via LogicalBoxModel; inheritance pass
propagates parent's WritingMode to descendants' WritingModeResolved;
sideways-rl falls back to vertical-rl layout (warn-once fires
observably but is not asserted).
Root-cause fix in inherit_writing_mode: Task 6 added WritingMode to
Style's Bundle, which made every Style-spawned entity a "set"
short-circuit in the Task 3 inheritance walk — descendants would
never inherit because their own default-valued WritingMode component
beat the ancestor lookup. Fix is CSS-faithful "default = inherit":
WritingMode::default() on an entity is treated as unset for
inheritance purposes, so the walk continues to the nearest non-
default ancestor. Spec § 2.2 wording ("its own WritingMode if set,
else the nearest ancestor's") now holds end-to-end.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
WritingMode+WritingModeResolvedship the writing-mode surface; sideways-* warn-once and fall back to vertical-rl/lr.BuiyLayoutStep::WritingModeInheritpipeline step (memoized multi-level ancestor walk) populates the resolved cache beforeSyncStyles. Layout pipeline goes from 8 to 9 steps.LogicalBoxModel+LogicalInsetergonomic builders translate logical → physical at construct time;LogicalEdgesis the underlying value type.Direction::Rtlwires throughtaffy::Style.direction, mirroring flex children under RTL.Style:.writing_mode(_),.writing_mode_kind(_),.direction(_),.ltr(),.rtl(),.text_orientation(_),.unicode_bidi(_).Test plan
cargo test --workspacegreenReferences
docs/plans/2026-05-10-buiy-layout-writing-modes.mddocs/specs/2026-05-08-buiy-layout-design/container-queries-and-writing-modes.md§ 2Notes from final branch review
inherit_writing_mode's ancestor walk treatsWritingMode::default()as "unset" (CSSinitial-like). Without this, everyStyle-spawned entity's bundledWritingMode::default()would short-circuit the walk so descendants would resolve to default instead of inheriting. Trade-off: an author cannot explicitly pinWritingMode::default()as an override against a non-default ancestor (observationally identical to inheriting the root default). Documented in CHANGELOG and inline insystems.rs::resolve_writing_mode.ContainingBlockcache — Phase 6 (anchor positioning) where it has a real consumer.LogicalBoxModel/LogicalInsettranslate at construct time only; runtime flips require re-spawn).buiy-text-rendering-design.buiy-i18n-design.HashMapallocation ininherit_writing_modeis acceptable for v1 (O(N) memoization is essential); aLocal<HashMap>with.clear()is a possible micro-optimization follow-up.🤖 Generated with Claude Code