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/*
* Copyright (C) 2025 Samuel Weinig <sam@webkit.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <wtf/OptionSet.h>
namespace WebCore {
class RenderStyle;
namespace Style {
// The difference between two styles. The following values are used:
// - DifferenceResult::Equal - The two styles are identical
// - DifferenceResult::RecompositeLayer - The layer needs its position and transform updated, but no repaint
// - DifferenceResult::Repaint - The object just needs to be repainted.
// - DifferenceResult::RepaintIfText - The object needs to be repainted if it contains text.
// - DifferenceResult::RepaintLayer - The layer and its descendant layers needs to be repainted.
// - DifferenceResult::LayoutOutOfFlowMovementOnly - Only the position of this out-of-flow box has been updated
// - DifferenceResult::Overflow - Only overflow needs to be recomputed
// - DifferenceResult::OverflowAndOutOfFlowMovement - Both out-of-flow movement and overflow updates are required.
// - DifferenceResult::Layout - A full layout is required.
enum class DifferenceResult : uint8_t {
Equal,
RecompositeLayer,
Repaint,
RepaintIfText,
RepaintLayer,
LayoutOutOfFlowMovementOnly,
Overflow,
OverflowAndOutOfFlowMovement,
Layout,
NewStyle
};
// When some style properties change, different amounts of work have to be done depending on
// context (e.g. whether the property is changing on an element which has a compositing layer).
// A simple DifferenceResult does not provide enough information so we return a bit mask of
// DifferenceContextSensitiveProperties from difference() as well.
enum class DifferenceContextSensitiveProperty : uint8_t {
Transform = 1 << 0,
Opacity = 1 << 1,
Filter = 1 << 2,
ClipRect = 1 << 3,
ClipPath = 1 << 4,
WillChange = 1 << 5,
};
struct Difference {
constexpr explicit Difference() = default;
constexpr Difference(DifferenceResult result, OptionSet<DifferenceContextSensitiveProperty> contextSensitiveProperties = { })
: result { result }
, contextSensitiveProperties { contextSensitiveProperties }
{
}
DifferenceResult result { DifferenceResult::Equal };
OptionSet<DifferenceContextSensitiveProperty> contextSensitiveProperties { };
bool operator==(const Difference&) const = default;
bool operator==(const DifferenceResult& other) const { return result == other; }
std::strong_ordering operator<=>(const Difference& other) const { return result <=> other.result; }
std::strong_ordering operator<=>(const DifferenceResult& other) const { return result <=> other; }
};
Difference difference(const RenderStyle&, const RenderStyle&);
bool differenceRequiresLayerRepaint(const RenderStyle&, const RenderStyle&, bool isComposited);
bool borderIsEquivalentForPainting(const RenderStyle&, const RenderStyle&);
WTF::TextStream& operator<<(WTF::TextStream&, Difference);
WTF::TextStream& operator<<(WTF::TextStream&, DifferenceResult);
WTF::TextStream& operator<<(WTF::TextStream&, DifferenceContextSensitiveProperty);
#if !LOG_DISABLED
void dumpDifferences(WTF::TextStream&, const RenderStyle&, const RenderStyle&);
#endif
} // namespace Style
} // namespace WebCore
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