fix(🐛): trim a path before stroking it

[dennytosp]

drawPath applies the stroke prop before start/end:

// packages/skia/src/sksg/Recorder/commands/Drawing.ts
if (hasFillType) { … }
if (hasStrokeOptions) { path = ctx.Skia.Path.Stroke(path, stroke); }   // 1st
if (hasStartOffset || hasEndOffset) { path = ctx.Skia.Path.Trim(path, start, end, false); }  // 2nd

Path.Stroke replaces the path with the outline of the stroke — a closed loop around it. Trimming afterwards walks that loop's perimeter, so start/end no longer refer to anything the caller drew.

<Path path="M 20 128 L 236 128" color="red" stroke={{ width: 20 }} start={0} end={0.5} />

x	expected	on main
60 (first half)	opaque	transparent
200 (second half)	transparent	opaque

end={0.5} paints the right half of the line — the halves are inverted, because half the outline's perimeter happens to land there.

The native recorder already gets this right — PathCmd::draw in cpp/api/recorder/Drawings.h runs trim → fill type → stroke:

if (hasStartOffset || hasEndOffset) { /* SkTrimPathEffect */ }
if (props.fillType.has_value()) { p->setFillType(...); }
if (hasStrokeOptions) { /* strokePaint.getFillPath */ }

So this is a JS-player divergence: Web and the static container were affected, iOS and Android were not.

Fix

Reorder the JS player to match: trim → fill type → stroke.

Tests

packages/skia/src/sksg/__tests__/PathTrim.spec.tsx renders the case above and samples both halves. It fails on main (Expected: 255, Received: 0) and passes with the fix.

No baselines move — nothing in the suite combined stroke with start/end, which is why this went unnoticed. Full suite: 747 passed, tsc --noEmit and eslint --max-warnings 0 clean.

[wcandillon]

Very nice catch :)
please use checkImage(img...) instead of expect(alphaAt(...

[dennytosp]

@wcandillon appreciate it! alphaAt is gone — the spec draws via surface.draw and compares with checkImage, and I added an untrimmed baseline next to the trimmed one so the two halves are easy to tell apart. Over to you whenever you have a moment ✌️

[wcandillon]

the native implementation side disappeared somehow? I added it back

[github-actions]

🎉 This PR is included in version 2.11.1 🎉

The release is available on:

• v2.11.1
• GitHub release

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