ladybird/Libraries/LibWeb/HTML/HTMLHRElement.cpp
Andreas Kling b981e6f7bc 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.
2024-12-24 17:17:09 +01:00

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1.5 KiB
C++

/*
* Copyright (c) 2018-2020, Andreas Kling <andreas@ladybird.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/Bindings/HTMLHRElementPrototype.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/CSS/ComputedProperties.h>
#include <LibWeb/CSS/StyleValues/LengthStyleValue.h>
#include <LibWeb/HTML/HTMLHRElement.h>
#include <LibWeb/HTML/Parser/HTMLParser.h>
namespace Web::HTML {
GC_DEFINE_ALLOCATOR(HTMLHRElement);
HTMLHRElement::HTMLHRElement(DOM::Document& document, DOM::QualifiedName qualified_name)
: HTMLElement(document, move(qualified_name))
{
}
HTMLHRElement::~HTMLHRElement() = default;
void HTMLHRElement::initialize(JS::Realm& realm)
{
Base::initialize(realm);
WEB_SET_PROTOTYPE_FOR_INTERFACE(HTMLHRElement);
}
bool HTMLHRElement::is_presentational_hint(FlyString const& name) const
{
if (Base::is_presentational_hint(name))
return true;
return first_is_one_of(name, HTML::AttributeNames::width);
}
void HTMLHRElement::apply_presentational_hints(GC::Ref<CSS::CascadedProperties> cascaded_properties) const
{
for_each_attribute([&](auto& name, auto& value) {
// https://html.spec.whatwg.org/multipage/rendering.html#the-hr-element-2:maps-to-the-dimension-property
if (name == HTML::AttributeNames::width) {
if (auto parsed_value = parse_dimension_value(value)) {
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::Width, *parsed_value);
}
}
});
}
}