LibWeb: Avoid many style invalidations on DOM attribute mutation

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

View file

@ -27,6 +27,14 @@ void HTMLParagraphElement::initialize(JS::Realm& realm)
WEB_SET_PROTOTYPE_FOR_INTERFACE(HTMLParagraphElement);
}
bool HTMLParagraphElement::is_presentational_hint(FlyString const& name) const
{
if (Base::is_presentational_hint(name))
return true;
return name == HTML::AttributeNames::align;
}
// https://html.spec.whatwg.org/multipage/rendering.html#tables-2
void HTMLParagraphElement::apply_presentational_hints(GC::Ref<CSS::CascadedProperties> cascaded_properties) const
{