Phase 2: layout overflow and scrolling#30
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10-task TDD plan realizing docs/specs/2026-05-08-buiy-layout-design/overflow-and-scrolling.md. Scope: 4 components (Overflow, Scroll, ScrollOffset, ScrollSnapItem) + 9 supporting enum types; Overflow → taffy::Style.overflow mapping per spec § 1.1; ScrollbarWidth → taffy::Style.scrollbar_width as f32 (12/8/0); Style Bundle extension with overflow + scroll fields and 12 fluent setters; sync_styles' change-detection trigger set widens to include Changed<Overflow> and Changed<Scroll> while excluding Changed<ScrollOffset> and Changed<ScrollSnapItem> — pinned by tests/layout_scroll_offset_no_invalidate.rs. Marks Phase 1 as [landed] and Phase 2 as [active] in docs/README.md. Spec: docs/specs/2026-05-08-buiy-layout-design/overflow-and-scrolling.md Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md
Two BLOCKERs: 1. Merged Tasks 5 (translate.rs widening) + 6 (systems.rs widening) into a single atomic Task 5 — splitting them left the lib uncompilable between commits because StyleView is the bridge between sync_styles' query and style_to_taffy. Renumbered remaining tasks 7→6, 8→7, 9→8, 10→9. 2. Fixed Task 8's ScrollOffset-no-invalidate test: ResolvedLayout derives only Clone (not Copy + PartialEq), so by-deref-value capture and direct assert_eq! both fail to compile. Switched to per-field (Vec2) capture and comparison; Vec2 has Copy + PartialEq. Nits: - Added rationale for ScrollbarWidth → f32 (Auto=12 / Thin=8 / None=0) matching common platform scrollbar widths. - Corrected the inline comment on map_overflow_mode regarding Taffy 0.10's Hidden/Clip distinction (Hidden reserves gutter, Clip doesn't). - Added a note to Task 2 explicitly directing executors to use #[reflect(Component, Default)] (matching BoxModel/Position/FlexParams), not #[reflect(Component)] (Phase 1's Display oversight). - Verified empirically that integration tests can use taffy::* without a dev-dep addition; documented in Task 7. - Cross-references in coverage map and body text updated for renumbering. - Final-note commit count corrected (10 = 9 task-commits + 1 plan-write). Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md
Adds OverflowMode, ScrollbarGutter, ScrollbarWidth, ScrollbarColor, ScrollBehavior, OverscrollBehavior, SnapType, SnapAlign, SnapStop — the supporting type surface for Phase 2 components in the next tasks. Spec: docs/specs/2026-05-08-buiy-layout-design/overflow-and-scrolling.md Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md task 1
Both ship with default = no-op (Visible/Visible, no snap). Overflow exposes is_scroll_container() — the spec § 1.2 predicate for sticky-positioning containing-block resolution (Phase 7). #[allow(dead_code)] on is_scroll_container: method is part of the documented public API and consumed in Phase 7; suppress the lint rather than silently remove or hide it. Spec: docs/specs/2026-05-08-buiy-layout-design/overflow-and-scrolling.md Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md task 2
ScrollOffset is runtime state — mutating it must not invalidate ResolvedLayout. ScrollSnapItem is child-side, like FlexItem; both stay decomposed-only (not in Style Bundle). Their exclusion from sync_styles' change-detection filter is enforced in Task 5. Spec: docs/specs/2026-05-08-buiy-layout-design/overflow-and-scrolling.md Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md task 3
Adds container-side overflow and scroll-snap fields plus 12 fluent setters. ScrollOffset (runtime) and ScrollSnapItem (child-side) stay out of the Bundle per architecture.md § 2.4. Spec: docs/specs/2026-05-08-buiy-layout-design/architecture.md § 2.2-2.4 Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md task 4
Atomic. Extends StyleView with `overflow` + `scroll`; maps OverflowMode
{Visible, Hidden, Clip, Scroll, Auto} → taffy::Overflow {Visible,
Hidden, Hidden, Scroll, Scroll} per spec § 1.1; ScrollbarWidth
{Auto, Thin, None} → 12.0 / 8.0 / 0.0 (f32).
Widens sync_styles' Or<(Changed<...>)> filter to include
Changed<Overflow> + Changed<Scroll>, matching architecture.md § 1.2.
Changed<ScrollOffset> and Changed<ScrollSnapItem> are intentionally
excluded — runtime state and child-side respectively (Task 8 asserts).
Spec: docs/specs/2026-05-08-buiy-layout-design/overflow-and-scrolling.md § 1.1
Spec: docs/specs/2026-05-08-buiy-layout-design/architecture.md § 1.2
Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md task 5
LayoutPlugin now reflects Overflow / Scroll / ScrollOffset / ScrollSnapItem; the four components and 9 supporting enums are re-exported from buiy_core and the buiy facade. Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md task 6
…ection End-to-end fixture: spawn Buiy entities with each OverflowMode variant, verify the resulting taffy::Style.overflow.x/y matches spec § 1.1 mapping. Adds doc-hidden by_entity / tree_ref accessors on LayoutTree to enable integration-test inspection of the Taffy bridge state. Spec: docs/specs/2026-05-08-buiy-layout-design/overflow-and-scrolling.md § 1, § 5 Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md task 7
…layout Pins Phase 2's central correctness invariant: mutating runtime/child-side scroll components must not enter sync_styles' trigger filter. Test mirrors the filter directly so future filter widenings against this contract surface in CI. Spec: docs/specs/2026-05-08-buiy-layout-design/overflow-and-scrolling.md § 2.1 Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md task 8
Adds Unreleased entries for the four new components, 9 enum types, Style Bundle extension, and the sync_styles trigger-set widening. Plan: docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.md task 9
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Summary
Phase 2 of the layout migration — ships overflow / scrolling component set on top of the Phase 1 foundation:
Overflow(per-axis overflow + scrollbar config),Scroll(snap container),ScrollOffset(runtime state),ScrollSnapItem(decomposed-only child-side).OverflowMode,ScrollbarGutter,ScrollbarWidth,ScrollbarColor,ScrollBehavior,OverscrollBehavior,SnapType,SnapAlign,SnapStop.OverflowMode::{Visible, Hidden, Clip, Scroll, Auto}→taffy::Overflow::{Visible, Hidden, Hidden, Scroll, Scroll}(per spec § 1.1);ScrollbarWidth::{Auto, Thin, None}→taffy::Style.scrollbar_width: f32(12.0 / 8.0 / 0.0).StyleBundle extension:OverflowandScrolljoin the Bundle (always-insert pattern from Phase 1) plus 12 fluent setters.ScrollOffsetandScrollSnapItemare decomposed-only per architecture.md § 2.4.sync_styles's change-detection trigger filter widens to includeChanged<Overflow>+Changed<Scroll>while deliberately excludingChanged<ScrollOffset>+Changed<ScrollSnapItem>— scroll-position mutations bypass the Taffy translate path entirely. The exclusion is pinned bycrates/buiy_core/tests/layout_scroll_offset_no_invalidate.rs, which mirrors the filter directly so any future widening against this contract surfaces in CI.Spec:
docs/specs/2026-05-08-buiy-layout-design/overflow-and-scrolling.mdPlan:
docs/plans/2026-05-08-buiy-layout-overflow-and-scrolling.mdTest plan
cargo fmt --all -- --checkcargo clippy --workspace --all-targets -- -D warningsRUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-depscargo test --workspace— 93 passed / 0 failed / 4 ignored (was 74 baseline; Phase 2 adds 19 tests)cargo deny checkOverflow::is_scroll_container()predicate matches spec § 1.2OverflowModevariants map to expectedtaffy::Overflowvalue through full pipelineScrollOffset/ScrollSnapItemdoes NOT triggersync_styles(yields 0 entities through the filter mirror)ResolvedLayoutis byte-equal across a scroll-only frameWorkflow
Authored via the project's superpowers skills:
writing-plansproduced the 9-task planResolvedLayoutonly derivesClone)subagent-driven-developmentwalked the 9 tasks with implementer → spec-reviewer → code-quality-reviewer cyclesOBSERVATIONSof the review)🤖 Generated with Claude Code