custom-canvas-and-gestureslisted

Enforces CustomPainter/Canvas discipline — the View/Painter/Scene split with a dumb painter fed one immutable Scene value type, shouldRepaint as a single value compare kept strictly separate from the AnimationController-as-repaint animation path, one shared affine transform read by BOTH painter and hit-tester (toCanvas/toLogical exact inverses, never re-derive scale), geometry hit-testing (integer lattice or rasterized region-ID buffer, never Path.contains), zero-allocation paint(), gesture-as-pure-translator emitting a typed command to a Notifier (never mutating in the handler), ExcludeSemantics + sibling Semantics speaking display values with redundant non-colour encoding, measured TextPainter fitting, first-party RoundedSuperellipseBorder, physical-pixel hairlines, and Directional-only geometry. Use when writing or reviewing a CustomPainter/CustomPaint, gestures on a canvas, tap/drag hit-testing, canvas animation, measured text fitting, or Semantics over custom-drawn pixels.
zakariaf/CatchLaw · ★ 0 · AI & Automation · score 55

Install: claude install-skill zakariaf/CatchLaw

# Custom Canvas & Gestures Hand-painted surfaces (`CustomPainter`/`Canvas`) own every pixel, so they look byte-identical across platforms — but only if the painter stays dumb, the coordinate math is shared, and gestures translate rather than decide. This skill is the contract for that layer: how it splits, how pixels and pointers agree, and how a screen reader hears a canvas. Read the reference for the task at hand: - `references/painter-and-scene.md` — the View/Painter/Scene split, the shared transform, hit-testing by geometry class, zero-allocation `paint()`, the two-path repaint pitfall. - `references/gestures-and-semantics.md` — gesture-as-translator, arena arbitration, clamp-not-collision drags, custom-canvas Semantics, action/gesture parity. - `references/text-and-shapes.md` — measured `TextPainter` fitting, optical centring, `RoundedSuperellipseBorder`, physical-pixel hairlines, concentric radii, painter-over-image-asset. Run `scripts/check_painter_hygiene.sh` and `scripts/analyze.sh` before a PR. ## Non-negotiable rules 1. **A canvas surface is three collaborators — a View, a Painter, and an immutable Scene — never one god-widget.** The View watches the ViewModel, builds an immutable `Scene` value type holding *everything the painter needs and nothing more*, and hands it to `CustomPaint`. The `Painter extends CustomPainter` is dumb: no `Notifier`, no `BuildContext`, no `DateTime`, no domain rules — it draws the Scene and never decides state. A dumb painter is tes