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LibWeb: Avoid many style invalidations on DOM attribute mutation

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Many times, attribute mutation doesn't necessitate a full style
invalidation on the element. However, the conditions are pretty
elaborate, so this first version has a lot of false positives.

We only need to invalidate style when any of these things apply:

1. The change may affect the match state of a selector somewhere.
2. The change may affect presentational hints applied to the element.

For (1) in this first version, we have a fixed list of attribute names
that may affect selectors. We also collect all names referenced by
attribute selectors anywhere in the document.

For (2), we add a new Element::is_presentational_hint() virtual that
tells us whether a given attribute name is a presentational hint.

This drastically reduces style work on many websites. As an example,
https://cnn.com/ is once again browseable.
This commit is contained in:
Andreas Kling 2024-12-23 17:51:10 +01:00 • committed by Andreas Kling
parent b11bdd4022
commit b981e6f7bc
Notes: github-actions[bot] 2024-12-24 16:18:00 +00:00
56 changed files with 377 additions and 37 deletions
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13
Libraries/LibWeb/SVG/SVGSymbolElement.cpp
View file

@ -39,11 +39,24 @@ void SVGSymbolElement::visit_edges(Cell::Visitor& visitor)
visitor.visit(m_view_box_for_bindings);
}
bool SVGSymbolElement::is_presentational_hint(FlyString const& name) const
{
if (Base::is_presentational_hint(name))
return true;
// FIXME: This is not a correct use of the presentational hint mechanism.
if (is_direct_child_of_use_shadow_tree())
return true;
return false;
}
// https://svgwg.org/svg2-draft/struct.html#SymbolNotes
void SVGSymbolElement::apply_presentational_hints(GC::Ref<CSS::CascadedProperties> cascaded_properties) const
{
Base::apply_presentational_hints(cascaded_properties);
// FIXME: This is not a correct use of the presentational hint mechanism.
if (is_direct_child_of_use_shadow_tree()) {
// The generated instance of a ‘symbol’ that is the direct referenced element of a ‘use’ element must always have a computed value of inline for the display property.
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::Display, CSS::DisplayStyleValue::create(CSS::Display::from_short(CSS::Display::Short::Inline)));