Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 69a399de80ab627e8f02ee00abd0e78904eec10c
https://github.com/WebKit/WebKit/commit/69a399de80ab627e8f02ee00abd0e78904eec10c
Author: Zak Ridouh <[email protected]>
Date: 2026-05-06 (Wed, 06 May 2026)
Changed paths:
A PerformanceTests/Layout/deep-nesting-overflow-siblings.html
M Source/WebCore/style/StyleTreeResolver.cpp
Log Message:
-----------
REGRESSION (297241@main): Overflow siblings at parser's max DOM tree depth
get fully rendered, causing slow layout
https://bugs.webkit.org/show_bug.cgi?id=314139
rdar://172219636
Reviewed by Sammy Gill and Alan Baradlay.
When the parser's DOM depth cap is reached, HTMLConstructionSite::attachLater
attaches further elements as siblings at the boundary depth (see 297241@main).
The render tree's depth check skipped elements above the cap but not at it,
so the overflow run was fully styled and laid out — causing ~15s render times
on content with thousands of overflow siblings (e.g. mail with embedded crash
logs containing unmatched <unavailable> tags).
At the maximum render tree depth, skip elements that have a previous element
sibling. The single legitimate deepest element keeps its renderer; the
overflow siblings get none.
* PerformanceTests/Layout/deep-nesting-overflow-siblings.html: Added.
* Source/WebCore/style/StyleTreeResolver.cpp:
(WebCore::Style::TreeResolver::resolveComposedTree):
Canonical link: https://commits.webkit.org/312751@main
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