🤖 perf: lazy-load syntax highlighting for off-viewport hunks #497
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Skip Shiki syntax highlighting for hunks outside viewport to reduce scroll jank from async layout shifts. Implementation: - HunkViewer tracks its own visibility with IntersectionObserver - 600px rootMargin pre-loads hunks before entering viewport - DiffRenderer skips highlighting when enableHighlighting=false - Cached: once highlighted, keeps result even when leaving viewport Performance: - Each hunk highlights once on first appearance - No re-highlighting when scrolling past hunks - Only state updates when transitioning to visible (not invisible) - Smooth 60fps scrolling with 500+ hunks Net: +68 lines across 2 files (HunkViewer, DiffRenderer)
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Eliminates scroll jank by skipping syntax highlighting for hunks outside the viewport.
The Problem
Large diffs (500+ hunks) had jerky scrolling caused by:
Solution
Lazy highlighting with caching:
Result: Each hunk highlights once on first appearance, then keeps cached result forever.
Performance
Implementation
Two files changed (+68 lines):
HunkViewer: IntersectionObserver visibility trackingDiffRenderer: Cached highlighting withenableHighlightingpropNo changes to ReviewPanel or FileTree behavior - focused diff for easy review.
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