RESOLVED DUPLICATE of bug 314376300697
[css-values] recompute animation keyframes if tree-counting functions are used 
https://bugs.webkit.org/show_bug.cgi?id=300697
Summary [css-values] recompute animation keyframes if tree-counting functions are used
Tim Nguyen (:ntim)
Reported 2025-10-14 06:44:19 PDT
If the number of DOM sibling changes in the middle of keyframes, we should re-compute `sibling-count()` and `sibling-index()`. https://wpt.fyi/results/css/css-values/tree-counting?label=master&label=experimental&aligned&q=keyframe
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Radar WebKit Bug Importer
Comment 1 2025-10-14 06:44:24 PDT
<rdar://problem/162599649>
Antoine Quint
Comment 2 2025-10-14 07:31:15 PDT
294062@main will be relevant here.
Antoine Quint
Comment 3 2025-11-07 01:34:04 PST
We have an existing system to determine whether a style change should require keyframes to be recomputed, see KeyframeEffect::recomputeKeyframesIfNecessary(). The question is whether comparing two `RenderStyle` objects will give us sufficient context to know when those functions would resolve to different values.
Ahmad Saleem
Comment 4 2026-05-08 10:29:50 PDT
I didn't notice this bug before fixing it as separate, so now duping to other. *** This bug has been marked as a duplicate of bug 314376 ***
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