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d27b43c1ee
Before:
`is<HTMLOLListElement>` and other similar calls in this commit
are resolved to `dynamic_cast`, which incurs runtime overhead
for resolving the type. The Performance hit becomes apparent
when rendering large lists. Callgrind analysis points to a
significant performance hit from calls to `is<...>` in
`Element::list_owner`.
Reference: Michael Gibbs and Bjarne Stroustrup (2006) Fast dynamic
casting. Softw. Pract. Exper. 2006; 36:139–156
After:
Implement inline `fast_is` virtual method that immediately
resolves the type. Results in noticeable performance improvement
2x-ish for lists with 20K entries.
Bonus: Convert starting value for LI elements to signed integer
The spec requires the start attribute and starting value to be
"integer". Firefox and Chrome support a negative start attribute.
FIXME: At the time of this PR, about 134 other objects resolve
`is<...>` to `dynamic_cast`. It may be a good idea to coordinate
similar changes to at least [some of] the ones that my have impact
on performance (maybe open a new issue?).
63 lines
2 KiB
C++
63 lines
2 KiB
C++
/*
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* Copyright (c) 2020, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/GenericShorthands.h>
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#include <LibWeb/HTML/HTMLElement.h>
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#include <LibWeb/HTML/HTMLOListElement.h>
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#include <LibWeb/HTML/HTMLUListElement.h>
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#include <LibWeb/WebIDL/Types.h>
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namespace Web::HTML {
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class HTMLLIElement final : public HTMLElement {
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WEB_PLATFORM_OBJECT(HTMLLIElement, HTMLElement);
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GC_DECLARE_ALLOCATOR(HTMLLIElement);
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public:
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virtual ~HTMLLIElement() override;
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// https://www.w3.org/TR/html-aria/#el-li
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virtual Optional<ARIA::Role> default_role() const override
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{
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for (auto ancestor = parent_element(); ancestor; ancestor = ancestor->parent_element()) {
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if (ancestor->role_or_default() == ARIA::Role::list)
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return ARIA::Role::listitem;
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}
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// https://w3c.github.io/core-aam/#roleMappingComputedRole
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// When an element has a role but is not contained in the required context (for example, an orphaned listitem
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// without the required accessible parent of role list), User Agents MUST ignore the role token, and return the
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// computedrole as if the ignored role token had not been included.
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return ARIA::Role::none;
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}
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WebIDL::Long value();
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void set_value(WebIDL::Long value)
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{
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MUST(set_attribute(AttributeNames::value, String::number(value)));
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}
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virtual bool is_html_li_element() const override { return true; }
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private:
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HTMLLIElement(DOM::Document&, DOM::QualifiedName);
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virtual void initialize(JS::Realm&) override;
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virtual void attribute_changed(FlyString const& local_name, Optional<String> const& old_value, Optional<String> const& value, Optional<FlyString> const& namespace_) override;
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virtual bool is_presentational_hint(FlyString const&) const override;
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virtual void apply_presentational_hints(GC::Ref<CSS::CascadedProperties>) const override;
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};
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}
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namespace Web::DOM {
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template<>
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inline bool Node::fast_is<Web::HTML::HTMLLIElement>() const { return is_html_li_element(); }
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}
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