Andreas Kling 5fd608b7cd LibWeb: Cache editability flag on DOM nodes for O(1) lookups ...

Add a cached m_in_editable_subtree flag to Node, updated on tree
mutations and contenteditable/designMode changes.

This replaces the recursive parent walk in is_editable() and
is_editing_host() with an O(1) flag check. The flag is recomputed
in inserted(), moved_from(), and cleared in removed_from(). Subtree
walks recompute the flag when contenteditable attributes change or
design mode is toggled.

This was 4% of CPU time while playing a YouTube video.

2026-02-21 03:51:28 +01:00

152 KiB

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