ladybird/Libraries/LibWeb/SVG/SVGSymbolElement.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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/*
* Copyright (c) 2023, Preston Taylor <95388976+PrestonLTaylor@users.noreply.github.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/Bindings/Intrinsics.h>
#include <LibWeb/Bindings/SVGSymbolElementPrototype.h>
#include <LibWeb/CSS/ComputedProperties.h>
#include <LibWeb/CSS/StyleValues/CSSKeywordValue.h>
#include <LibWeb/CSS/StyleValues/DisplayStyleValue.h>
#include <LibWeb/CSS/StyleValues/ShorthandStyleValue.h>
#include <LibWeb/DOM/ShadowRoot.h>
#include <LibWeb/Layout/SVGGraphicsBox.h>
#include <LibWeb/SVG/AttributeNames.h>
#include <LibWeb/SVG/SVGAnimatedRect.h>
#include <LibWeb/SVG/SVGSymbolElement.h>
#include <LibWeb/SVG/SVGUseElement.h>
namespace Web::SVG {
GC_DEFINE_ALLOCATOR(SVGSymbolElement);
SVGSymbolElement::SVGSymbolElement(DOM::Document& document, DOM::QualifiedName qualified_name)
: SVGGraphicsElement(document, qualified_name)
{
}
void SVGSymbolElement::initialize(JS::Realm& realm)
{
Base::initialize(realm);
WEB_SET_PROTOTYPE_FOR_INTERFACE(SVGSymbolElement);
m_view_box_for_bindings = realm.create<SVGAnimatedRect>(realm);
}
void SVGSymbolElement::visit_edges(Cell::Visitor& visitor)
{
Base::visit_edges(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)));
}
}
void SVGSymbolElement::attribute_changed(FlyString const& name, Optional<String> const& old_value, Optional<String> const& value, Optional<FlyString> const& namespace_)
{
Base::attribute_changed(name, old_value, value, namespace_);
if (name.equals_ignoring_ascii_case(SVG::AttributeNames::viewBox)) {
m_view_box = try_parse_view_box(value.value_or(String {}));
m_view_box_for_bindings->set_nulled(!m_view_box.has_value());
if (m_view_box.has_value()) {
m_view_box_for_bindings->set_base_val(Gfx::DoubleRect { m_view_box->min_x, m_view_box->min_y, m_view_box->width, m_view_box->height });
m_view_box_for_bindings->set_anim_val(Gfx::DoubleRect { m_view_box->min_x, m_view_box->min_y, m_view_box->width, m_view_box->height });
}
}
}
bool SVGSymbolElement::is_direct_child_of_use_shadow_tree() const
{
auto maybe_shadow_root = parent();
if (!is<DOM::ShadowRoot>(maybe_shadow_root)) {
return false;
}
auto host = static_cast<const DOM::ShadowRoot&>(*maybe_shadow_root).host();
return is<SVGUseElement>(host);
}
GC::Ptr<Layout::Node> SVGSymbolElement::create_layout_node(GC::Ref<CSS::ComputedProperties> style)
{
return heap().allocate<Layout::SVGGraphicsBox>(document(), *this, move(style));
}
}