fix(renderer): delete CanvasKit Shader/PathEffect/ColorFilter objects to prevent WASM heap OOM

[Postroggy]

Problem

When rendering a large number of nodes (e.g. 800+ component variants from a Figma library), the CanvasKit WASM heap grows linearly until it is exhausted, crashing with:

RuntimeError: Aborted()

The crash occurs after rendering ~100–200 nodes depending on component complexity.

Root Cause

CanvasKit uses manual ref-counted memory on the WASM heap. Every object created via ck.Shader.MakeLinearGradient(...), ck.PathEffect.MakeDash(...), ck.ColorFilter.MakeMatrix(...), etc. must be explicitly .delete()d.

The bug: after calling paint.setShader(shader) / paint.setPathEffect(effect) / paint.setColorFilter(cf), the JS-side handle was never deleted. paint.delete() only decrements the Paint's own ref — the underlying Skia object held by the JS variable is never freed.

Internally, paint.setShader(shader) calls SkRef() on the C++ side (refcount → 2). When the paint is deleted, refcount drops to 1. Without shader.delete(), the WASM heap object is permanently leaked. Across hundreds of render calls this exhausts the WASM heap.

Fix

Add .delete() immediately after each set*() call — safe because the Paint holds its own internal SkRef. 13 sites fixed in node-renderer.ts:

Method	Object type	Location
makeFillPaint	Shader (linear gradient)	line ~175
makeFillPaint	Shader (radial gradient)	line ~201
applyImageFillToPaint	Shader (tile image)	line ~281
applyImageFillToPaint	ColorFilter (image adjust)	line ~284
drawImageFillRect	ColorFilter (image adjust)	line ~316
makeStrokePaint	PathEffect (dash)	line ~437
drawEllipse	PathEffect (corner) × 2	lines ~687, ~695
drawPolygon	PathEffect (corner) × 2	lines ~780, ~788
drawImage	ColorFilter (image adjust)	line ~1028
drawImage	Shader (tile image)	line ~1041
drawImageFallback	PathEffect (dash)	line ~1116

Pattern applied

// Before (leaked)
const shader = ck.Shader.MakeLinearGradient(...);
if (shader) paint.setShader(shader);

// After (fixed)
const shader = ck.Shader.MakeLinearGradient(...);
if (shader) { paint.setShader(shader); shader.delete(); }

Verification

Tested rendering 800+ Figma component variants in a single batch run. Before fix: crash at ~181 nodes. After fix: all nodes render successfully with stable memory usage.

[Kayshen-X]

Thank you for your submission, but we are rewriting this program using Rust, so your submission may be temporarily irrelevant. You can refer to the v0.8.0 branch if you're interested.