fix: coalesce scan() into a single rAF to avoid paint delay on bulk DOM mutations#344
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manuelpuyol merged 4 commits intomainfrom Apr 20, 2026
Merged
fix: coalesce scan() into a single rAF to avoid paint delay on bulk DOM mutations#344manuelpuyol merged 4 commits intomainfrom
manuelpuyol merged 4 commits intomainfrom
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…OM mutations Replace per-element WeakMap+rAF deduplication with a shared Set of pending elements and a single requestAnimationFrame timer. When many elements are added in one frame (e.g. framework list rendering), only one rAF callback now runs before paint instead of one per element. Fixes #343 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR addresses performance regressions in lazyDefine by coalescing scan() work into a single requestAnimationFrame callback per frame, reducing pre-paint rAF flooding during bulk DOM insertions (Fixes #343).
Changes:
- Replaced per-element rAF deduplication (
WeakMap) with a sharedSetof pending elements and a single rAF timer. - Updated
scan()to process all pending elements in one rAF callback. - Added a test asserting that bulk element insertion does not schedule one rAF per element.
Show a summary per file
| File | Description |
|---|---|
src/lazy-define.ts |
Coalesces multiple scan() calls into a single rAF callback using a shared pending set. |
test/lazy-define.ts |
Adds coverage to ensure bulk-added elements don’t cause excessive rAF scheduling. |
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- Files reviewed: 2/2 changed files
- Comments generated: 3
manuelpuyol
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Apr 17, 2026
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the copilot comments look valid to me
manuelpuyol
approved these changes
Apr 20, 2026
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Summary
Fixes #343
When many elements are added to the DOM in a single frame (e.g. a framework rendering a list), the
scan()function inlazy-define.tswas scheduling a separaterequestAnimationFramecallback for each element. Since all rAF callbacks run before the browser paints, this delayed the first paint proportionally to the number of added elements.Changes
Replaced the per-element
WeakMap+requestAnimationFramededuplication with:Set<ElementLike>that collects pending elementsrequestAnimationFrametimer that processes all pending elements in one callbackThis ensures that no matter how many elements are added in a single frame, only one rAF callback runs before paint.
Testing
Added a test that verifies multiple elements added at once are coalesced into minimal rAF calls rather than one per element. All existing tests continue to pass.