@remotion/web-renderer: Fix opacity leaking between layers

[JonnyBurger]

Summary

• restore the overflow: hidden canvas state before resetting opacity so a fading layer cannot leak alpha into later siblings
• add a cross-browser regression test for an opaque layer covering a fading clipped layer

Testing

• bun run build
• bun run stylecheck
• bun run testwebrenderer (648 passed, 21 skipped)

[vercel]

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Project	Deployment	Actions	Updated (UTC)
bugs	Building	Preview, Comment	Jul 24, 2026 9:58am
remotion	Ready	Preview, Comment	Jul 24, 2026 9:58am

[pullfrog]

Reviewed changes — fixes opacity leaking between layers in the web-renderer canvas compositor by reordering cleanup so that ctx.restore() from overflow: hidden runs before manual opacity and filter resets, and adds a cross-browser regression test.

• Fix cleanupAfterChildren order in drawElement — calls finishOverflowHidden() before finishFilter() and finishOpacity() so the canvas state restore from overflow: hidden cannot reapply a parent's opacity/filter after they've been cleared.
• Add opaque-layer-over-fading-layer test fixture and test — renders a 0.3-opacity blue layer beneath an opaque red layer, asserts the center pixel is solid red, and snapshots across Chromium, Firefox, and WebKit.

✅ No new issues found.

  ^{｜ View workflow run ｜ Using DeepSeek Pro (free via Pullfrog for OSS) (Claude Opus not used — the program covers this model; add its provider key to run your pick) ｜ 𝕏}

[pullfrog]

Reviewed changes — adds generated screenshot baselines for the new opacity regression test across Chromium, Firefox, and WebKit on Darwin, and wires up testImage snapshot comparison in the test file.

• Add screenshot baselines — three PNG snapshots (chromium-darwin, firefox-darwin, webkit-darwin) generated from the opaque-layer-over-fading-layer test.
• Wire up testImage — adds the import and snapshot comparison call in opaque-layer-over-fading-layer.test.tsx.

✅ No new issues found.

  ^{｜ View workflow run ｜ Using DeepSeek Pro (free via Pullfrog for OSS) (Claude Opus not used — the program covers this model; add its provider key to run your pick) ｜ 𝕏}