ladybird/Libraries/LibWeb/HTML/HTMLPreElement.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

49 lines
1.4 KiB
C++

/*
* Copyright (c) 2020, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/Bindings/HTMLPreElementPrototype.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/CSS/ComputedProperties.h>
#include <LibWeb/CSS/StyleValues/CSSKeywordValue.h>
#include <LibWeb/HTML/HTMLPreElement.h>
#include <LibWeb/HTML/Numbers.h>
namespace Web::HTML {
GC_DEFINE_ALLOCATOR(HTMLPreElement);
HTMLPreElement::HTMLPreElement(DOM::Document& document, DOM::QualifiedName qualified_name)
: HTMLElement(document, move(qualified_name))
{
}
HTMLPreElement::~HTMLPreElement() = default;
void HTMLPreElement::initialize(JS::Realm& realm)
{
Base::initialize(realm);
WEB_SET_PROTOTYPE_FOR_INTERFACE(HTMLPreElement);
}
bool HTMLPreElement::is_presentational_hint(FlyString const& name) const
{
if (Base::is_presentational_hint(name))
return true;
return name == HTML::AttributeNames::wrap;
}
void HTMLPreElement::apply_presentational_hints(GC::Ref<CSS::CascadedProperties> cascaded_properties) const
{
HTMLElement::apply_presentational_hints(cascaded_properties);
for_each_attribute([&](auto const& name, auto const&) {
if (name.equals_ignoring_ascii_case(HTML::AttributeNames::wrap))
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::WhiteSpace, CSS::CSSKeywordValue::create(CSS::Keyword::PreWrap));
});
}
}