Andreas Kling f10f651e49 LibWeb: Don't treat first media-query evaluation as a flip ...

CSSStyleSheet::evaluate_media_queries previously flagged "no recorded
result yet" as a match-state change, so every freshly-loaded sheet
fired MediaQueryChangedMatchState on the first pass through
Document::evaluate_media_rules. For sheets added through
adoptedStyleSheets that piled an extra full-document style invalidation
on top of the AdoptedStyleSheetsList one, recomputing every element a
second time for nothing.

Drop the !has_value() leg so the very first evaluation establishes the
baseline silently. The sheet's rules already entered the cascade through
StyleSheetListAddSheet, AdoptedStyleSheetsList, or invalidate_owners,
each of which performs its own targeted invalidation.

Two callers relied on the implicit "first eval forces a refresh"
behavior to handle freshly-mutated state:

- invalidate_owners resets m_did_match, then leans on the next eval to
  repopulate it. With the new semantics it must also re-evaluate the
  sheet eagerly so MediaList::matches() and inner @media state are
  fresh before the next rule cache build reads them.
- The adoptedStyleSheets on_set callback didn't evaluate at all,
  relying on Document::evaluate_media_rules to populate
  MediaList::m_matches. That worked accidentally because the false
  flip retriggered invalidate_rule_cache after the matches had been
  populated. Mirror StyleSheetList::add_sheet by evaluating the sheet
  at adopt time so the rule cache build sees the correct match state
  even if it runs first (e.g. via a :has() invalidation pass).

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

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