ladybird/Libraries/LibWeb/HTML/HTMLMarqueeElement.h
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) 2020, the SerenityOS developers.
* Copyright (c) 2024, Jamie Mansfield <jmansfield@cadixdev.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <LibWeb/HTML/HTMLElement.h>
#include <LibWeb/WebIDL/Types.h>
namespace Web::HTML {
// NOTE: This element is marked as obsolete, but is still listed as required by the specification.
class HTMLMarqueeElement final : public HTMLElement {
WEB_PLATFORM_OBJECT(HTMLMarqueeElement, HTMLElement);
GC_DECLARE_ALLOCATOR(HTMLMarqueeElement);
public:
virtual ~HTMLMarqueeElement() override;
WebIDL::UnsignedLong scroll_amount();
WebIDL::ExceptionOr<void> set_scroll_amount(WebIDL::UnsignedLong);
WebIDL::UnsignedLong scroll_delay();
WebIDL::ExceptionOr<void> set_scroll_delay(WebIDL::UnsignedLong);
private:
HTMLMarqueeElement(DOM::Document&, DOM::QualifiedName);
virtual void initialize(JS::Realm&) override;
virtual bool is_presentational_hint(FlyString const&) const override;
virtual void apply_presentational_hints(GC::Ref<CSS::CascadedProperties>) const override;
};
}