Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: b71cc01dd5ba9c5971f161436349097259db9270
https://github.com/WebKit/WebKit/commit/b71cc01dd5ba9c5971f161436349097259db9270
Author: Ahmad Saleem <[email protected]>
Date: 2026-10-05 (Mon, 05 Oct 2026)
Changed paths:
M
LayoutTests/imported/w3c/web-platform-tests/css/css-cascade/scope-invalidation-expected.txt
M
LayoutTests/imported/w3c/web-platform-tests/css/css-cascade/scope-invalidation.html
M Source/WebCore/style/ElementRuleCollector.cpp
Log Message:
-----------
@scope start (scoping root) selector matching drops style relations, so
structural DOM mutations don't invalidate scope membership
https://bugs.webkit.org/show_bug.cgi?id=325287
rdar://188398757
Reviewed by Antti Koivisto.
ElementRuleCollector::ruleMatches() merges the style relations recorded
during selector matching into m_styleRelations, which are later committed
(commitRelationsToRenderStyle / commitRelations) to set flags such as
childrenAffectedByForwardPositionalRules, styleAffectedByEmpty, and
childIndex on the relevant elements. ChildChangeInvalidation reads those
flags to decide whether a structural DOM mutation (child insertion or
removal) must re-evaluate positional or :empty selectors.
ElementRuleCollector::scopeRulesMatch() matches the @scope prelude
(scoping root) selector against ancestors using a local CheckingContext,
but never merged the style relations it accumulated into m_styleRelations.
As a result, when a scoping root selector used a structural pseudo-class
(:nth-child(), :empty, :first-child, ...), the corresponding affected-by
flags were never set, and a later structural mutation that changed which
element is a scoping root failed to invalidate, leaving stale styles.
Merge the style relations recorded while matching the scoping root
selector into m_styleRelations, mirroring ruleMatches(). Relations are
committed after each match (including non-matches, since those
dependencies still drive future invalidation) and the buffer is cleared
between calls to avoid duplicate accumulation in the reused context.
*
LayoutTests/imported/w3c/web-platform-tests/css/css-cascade/scope-invalidation-expected.txt:
*
LayoutTests/imported/w3c/web-platform-tests/css/css-cascade/scope-invalidation.html:
* Source/WebCore/style/ElementRuleCollector.cpp:
(WebCore::Style::ElementRuleCollector::scopeRulesMatch):
Canonical link: https://commits.webkit.org/322680@main
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