webcanvas: memory safety++

[tinyjin]

When dispose() was called explicitly and GC fired afterward, the FinalizationRegistry callback would call _tvg_paint_unref / _tvg_gradient_del again on the already-freed pointer, corrupting the WASM heap.

const shape = new TVG.Shape();
shape.appendRect(0, 0, 100, 100).fill(255, 0, 0, 255);
canvas.add(shape);

// User explicitly cleans up
shape.dispose();

// Later, GC collects the Shape object and FinalizationRegistry fires
// calls _tvg_paint_unref on the already-freed pointer -> double-free

This PR adds:

• Fixes issue by invalidating registry token (ptr = 0) on dispose() so FinalizationRegistry callback becomes a no-op
• Adds test cases to ensure WASM object memory safety

[Copilot]

Pull request overview

This PR improves WASM-backed object memory safety by preventing double-free scenarios between manual dispose() and FinalizationRegistry-driven cleanup, and adds tests to validate GC-based cleanup behavior.

Changes:

• Refactors FinalizationRegistry setup to share logic and avoid capturing this via bound cleanup functions.
• Updates WasmObject.dispose() to invalidate the finalizer token pointer after manual cleanup.
• Adds GC/double-free regression tests plus a shared test helper, and enables --expose-gc for the Node test runner.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
packages/webcanvas/vitest.config.ts	Enables exposed GC for Node-based Vitest runs.
packages/webcanvas/src/interop/registry.ts	Deduplicates registry construction via createRegistry().
packages/webcanvas/src/interop/WasmObject.ts	Stores a mutable registry token and zeros ptr on dispose to avoid double-free.
packages/webcanvas/test/helpers.ts	Adds utilities to force finalization and assert GC cleanup / no double-free.
packages/webcanvas/test/text.test.ts	Adds dispose+GC and GC-cleanup tests for Text.
packages/webcanvas/test/shape.test.ts	Adds dispose+GC and GC-cleanup tests for Shape.
packages/webcanvas/test/scene.test.ts	Adds dispose+GC and GC-cleanup tests for Scene.
packages/webcanvas/test/picture.test.ts	Adds dispose+GC and GC-cleanup tests for Picture.
packages/webcanvas/test/gradient.test.ts	Adds dispose+GC and GC-cleanup tests for gradients.

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[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

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[github-actions]

🚀 Playground preview deployment ready!

🎮 Playground: https://thorvg-playground-rdod1sn0e-thorvg-web.vercel.app

[tinyjin]

Hold, I've found minor issue. Under reviewing.

[github-actions]

🚀 Playground preview deployment ready!

🎮 Playground: https://thorvg-playground-4zqz89iov-thorvg-web.vercel.app

[github-actions]

🚀 Playground preview deployment ready!

🎮 Playground: https://thorvg-playground-p89jvez8u-thorvg-web.vercel.app

[github-actions]

🚀 Playground preview deployment ready!

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[github-actions]

🚀 Playground preview deployment ready!

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[Copilot]

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[github-actions]

🚀 Playground preview deployment ready!

🎮 Playground: https://thorvg-playground-rigjmp6oi-thorvg-web.vercel.app