ladybird/Libraries/LibWeb/HTML/HTMLEmbedElement.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

83 lines
3.5 KiB
C++

/*
* Copyright (c) 2020, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/Bindings/HTMLEmbedElementPrototype.h>
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/CSS/ComputedProperties.h>
#include <LibWeb/CSS/StyleValues/CSSKeywordValue.h>
#include <LibWeb/CSS/StyleValues/DisplayStyleValue.h>
#include <LibWeb/HTML/HTMLEmbedElement.h>
#include <LibWeb/HTML/Parser/HTMLParser.h>
namespace Web::HTML {
GC_DEFINE_ALLOCATOR(HTMLEmbedElement);
HTMLEmbedElement::HTMLEmbedElement(DOM::Document& document, DOM::QualifiedName qualified_name)
: HTMLElement(document, move(qualified_name))
{
}
HTMLEmbedElement::~HTMLEmbedElement() = default;
void HTMLEmbedElement::initialize(JS::Realm& realm)
{
Base::initialize(realm);
WEB_SET_PROTOTYPE_FOR_INTERFACE(HTMLEmbedElement);
}
bool HTMLEmbedElement::is_presentational_hint(FlyString const& name) const
{
if (Base::is_presentational_hint(name))
return true;
return first_is_one_of(name,
HTML::AttributeNames::align,
HTML::AttributeNames::height,
HTML::AttributeNames::hspace,
HTML::AttributeNames::vspace,
HTML::AttributeNames::width);
}
void HTMLEmbedElement::apply_presentational_hints(GC::Ref<CSS::CascadedProperties> cascaded_properties) const
{
for_each_attribute([&](auto& name, auto& value) {
if (name == HTML::AttributeNames::align) {
if (value.equals_ignoring_ascii_case("center"sv))
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::TextAlign, CSS::CSSKeywordValue::create(CSS::Keyword::Center));
else if (value.equals_ignoring_ascii_case("middle"sv))
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::TextAlign, CSS::CSSKeywordValue::create(CSS::Keyword::Middle));
} else if (name == HTML::AttributeNames::height) {
if (auto parsed_value = parse_dimension_value(value))
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::Height, *parsed_value);
}
// https://html.spec.whatwg.org/multipage/rendering.html#attributes-for-embedded-content-and-images:maps-to-the-dimension-property
else if (name == HTML::AttributeNames::hspace) {
if (auto parsed_value = parse_dimension_value(value)) {
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::MarginLeft, *parsed_value);
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::MarginRight, *parsed_value);
}
} else if (name == HTML::AttributeNames::vspace) {
if (auto parsed_value = parse_dimension_value(value)) {
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::MarginTop, *parsed_value);
cascaded_properties->set_property_from_presentational_hint(CSS::PropertyID::MarginBottom, *parsed_value);
}
} else 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);
}
}
});
}
void HTMLEmbedElement::adjust_computed_style(CSS::ComputedProperties& style)
{
// https://drafts.csswg.org/css-display-3/#unbox
if (style.display().is_contents())
style.set_property(CSS::PropertyID::Display, CSS::DisplayStyleValue::create(CSS::Display::from_short(CSS::Display::Short::None)));
}
}