Eliminate layout work during TOC scrolling#3677
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Cache heading and TOC geometry outside the scroll path so long release-note pages remain responsive without changing active-section behavior. Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com> Co-authored-by: Cursor <cursoragent@cursor.com>
Mpdreamz
approved these changes
Jul 21, 2026
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Why
Long release-note pages contain hundreds of headings, and reading heading and TOC geometry while scrolling can repeatedly force expensive layout work. The active section should update without touching layout on the scroll path.
What
Cache heading and TOC geometry outside scrolling, then use binary searches over document positions to select the active links. Refresh the cache only when viewport or content layout changes, keep the progress indicator transform-only, and apply active styling directly to TOC items without descendant
:has()matching.Test plan
npm run test -- --runInBand Assets/toc-nav.test.tsMade with Cursor