Andreas Kling 57d9668bca LibWeb: Don't treat first @media rule evaluation as a flip ...

CSSRuleList::evaluate_media_queries previously compared
CSSMediaRule::condition_matches() (which reads MediaQuery::m_matches,
default false) against the freshly-computed result. A brand-new @media
rule whose condition matches would therefore look like a false->true
flip the very first time it was evaluated, the same shape as the
CSSStyleSheet outer-MediaList bug fixed in the previous commit.

In practice all known paths that introduce a new @media rule
(StyleSheetList::add_sheet, AdoptedStyleSheets on_set,
CSSStyleSheet::invalidate_owners, CSSImportRule::set_style_sheet) call
through CSSStyleSheet::evaluate_media_queries eagerly and absorb the
flip before the next Document::evaluate_media_rules pass, so this
change does not move counters in the existing tests. It does make the
inner-@media handling consistent with the outer one, and protects any
future path (e.g. CSSGroupingRule::insert_rule into a nested rule
list) where a new @media rule might be evaluated for the first time
during the regular media-rule pass.

Track per-rule whether evaluate has been called yet via a sticky
m_did_evaluate flag on CSSMediaRule, and only record a flip on
subsequent evaluations.

2026-04-28 19:06:29 +02:00

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