Tim Ledbetter 6bb037aec7 LibWeb: Skip backward sibling invalidation when no child needs it ...

We now track when a parent has a child affected by a backward structural
pseudo-class. These are selectors whose match result for an element can
depend on siblings after that element, such as `:last-child`,
`:only-child`, `:last-of-type`, `:only-of-type`, `:nth-last-child`, and
`:nth-last-of-type`.

When inserting or removing a node, previous siblings only need style
invalidation if one of them was matched against such a selector. Use the
parent-level flag to skip the previous-sibling walk when no child under
that parent can be affected.

This saves a lot of invalidation work on sites that insert a lot of
nodes into the DOM via JS.

2026-04-26 16:14:43 +02:00

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