Andreas Kling 4a7ca32af0 LibWeb: Skip full document style update in getComputedStyle if possible ...

Before calling update_style() for a getComputedStyle property access,
we now check whether the target element actually needs a style update
by walking the flat tree ancestor chain. If neither the element nor any
of its ancestors have dirty style bits, and there are no document-level
reasons to recalculate style, we skip the update_style() call entirely.

We walk the flat tree (not the DOM tree) because style inheritance
follows slot assignment -- slotted elements inherit from their assigned
slot, not their DOM parent.

This avoids unnecessary work when scripts access computed style
properties on elements whose styles are already up-to-date, which is a
common pattern on the web.

2026-02-13 10:22:30 +01:00

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