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LibWeb: Limit sibling style invalidation by max distance

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If an element is affected only by selectors using the direct sibling
combinator `+`, we can calculate the maximum invalidation distance and
use it to limit style invalidation. For example, the selector
`.a + .b + .c` has a maximum invalidation distance of 2, meaning we can
skip invalidating any element affected by this selector if it's more
than two siblings away from the element that triggered the style
invalidation.

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This commit is contained in:
Aliaksandr Kalenik 2025-03-10 16:16:08 +01:00 • committed by Alexander Kalenik
parent 46abdd1126
commit 84ecaaa75c
Notes: github-actions[bot] 2025-03-10 17:57:49 +00:00
6 changed files with 61 additions and 10 deletions
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30
Libraries/LibWeb/CSS/Selector.cpp
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@ -765,6 +765,36 @@ Optional<Selector::SimpleSelector> Selector::SimpleSelector::absolutized(Selecto
VERIFY_NOT_REACHED();
}
size_t Selector::sibling_invalidation_distance() const
{
if (m_sibling_invalidation_distance.has_value())
return *m_sibling_invalidation_distance;
m_sibling_invalidation_distance = 0;
size_t current_distance = 0;
for (auto const& compound_selector : compound_selectors()) {
if (compound_selector.combinator == Combinator::None)
continue;
if (compound_selector.combinator == Combinator::SubsequentSibling) {
m_sibling_invalidation_distance = NumericLimits<size_t>::max();
return *m_sibling_invalidation_distance;
}
if (compound_selector.combinator == Combinator::NextSibling) {
current_distance++;
} else {
m_sibling_invalidation_distance = max(*m_sibling_invalidation_distance, current_distance);
current_distance = 0;
}
}
if (current_distance > 0) {
m_sibling_invalidation_distance = max(*m_sibling_invalidation_distance, current_distance);
}
return *m_sibling_invalidation_distance;
}
SelectorList adapt_nested_relative_selector_list(SelectorList const& selectors)
{
// "Nested style rules differ from non-nested rules in the following ways: