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/*
* Copyright (C) 2025 Apple Inc. All rights reserved.
*
* 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. AND ITS CONTRIBUTORS ``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 ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 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.
*/
#include "config.h"
#include "MatchResultCache.h"
#include "MatchResult.h"
#include "ResolvedStyle.h"
#include "StyleProperties.h"
#include "StyledElement.h"
#include <wtf/BitSet.h>
namespace WebCore {
namespace Style {
// Cache entries contain a MatchResult object that references element's mutable inline style.
// As a result the cache entry mutates when element's inline style mutates.
// We save the original properties and values so we can check which properties have changed.
// If a property changes we null the value and assume it will change in the future too.
//
// It would be nicer if the cache entries were immutable but doing that in a sufficiently
// performant way is tricky.
struct OriginalInlineProperty {
CSSPropertyID propertyID;
RefPtr<const CSSValue> valueIfUnchanged;
};
struct MatchResultCache::Entry : CanMakeCheckedPtr<MatchResultCache::Entry> {
UnadjustedStyle unadjustedStyle;
Ref<const MutableStyleProperties> inlineStyle;
Vector<OriginalInlineProperty> originalInlineProperties;
Entry(UnadjustedStyle&& unadjustedStyle, const MutableStyleProperties& inlineStyle)
: unadjustedStyle(WTFMove(unadjustedStyle))
, inlineStyle(inlineStyle)
{
originalInlineProperties.reserveInitialCapacity(inlineStyle.size());
for (auto property : inlineStyle) {
originalInlineProperties.append({
.propertyID = property.id(),
.valueIfUnchanged = property.value()
});
}
}
WTF_STRUCT_OVERRIDE_DELETE_FOR_CHECKED_PTR(Entry);
WTF_DEPRECATED_MAKE_STRUCT_FAST_ALLOCATED(MatchResultCache);
};
MatchResultCache::MatchResultCache() = default;
MatchResultCache::~MatchResultCache() = default;
inline UnadjustedStyle copy(const UnadjustedStyle& other)
{
return {
.style = RenderStyle::clonePtr(*other.style),
.relations = other.relations ? makeUnique<Relations>(*other.relations) : std::unique_ptr<Relations> { },
.matchResult = other.matchResult
};
}
bool MatchResultCache::isUsableAfterInlineStyleChange(const MatchResultCache::Entry& entry, const StyleProperties& currentInlineStyle)
{
if (entry.inlineStyle.ptr() != ¤tInlineStyle)
return false;
Ref inlineStyle = entry.inlineStyle;
// Only allow the same exact properties after a change. This way the previous values in RenderStyle are guranteed to get overwritten.
// Adding properties could be allowed without other changes. Removal would require resetting the removed property to initial
// value in the style builder.
auto size = entry.originalInlineProperties.size();
if (size != inlineStyle->size())
return false;
for (size_t index = 0; index < size; ++index) {
if (entry.originalInlineProperties[index].propertyID != inlineStyle->propertyAt(index).id())
return false;
}
return true;
}
PropertyCascade::IncludedProperties MatchResultCache::computeAndUpdateChangedProperties(MatchResultCache::Entry& entry)
{
auto& originalProperties = entry.originalInlineProperties;
auto& inlineStyle = entry.inlineStyle.get();
PropertyCascade::IncludedProperties result;
auto size = originalProperties.size();
for (size_t index = 0; index < size; ++index) {
auto currentProperty = inlineStyle.propertyAt(index);
auto propertyID = currentProperty.id();
ASSERT(originalProperties[index].propertyID == propertyID);
if (originalProperties[index].valueIfUnchanged == currentProperty.value())
continue;
// Assume that if a value changes ones then it will change more. Don't track changes anymore.
originalProperties[index].valueIfUnchanged = nullptr;
// FIXME: Support custom properties.
if (propertyID == CSSPropertyCustom)
return PropertyCascade::normalProperties();
// Only use partial applying with low-priority properties since we know changes to them can't
// affect values of other properties.
// FIXME: CSSPropertyLineHeight shouldn't be a low-priority property as others can depend on it via `lh` unit.
if (propertyID < firstLowPriorityProperty || propertyID == CSSPropertyLineHeight)
return PropertyCascade::normalProperties();
result.ids.append(propertyID);
}
return result;
}
const std::optional<CachedMatchResult> MatchResultCache::resultWithCurrentInlineStyle(const Element& element)
{
auto it = m_entries.find(element);
if (it == m_entries.end())
return { };
auto& entry = it->value;
auto* styledElement = dynamicDowncast<StyledElement>(element);
RefPtr inlineStyle = styledElement ? styledElement->inlineStyle() : nullptr;
if (!inlineStyle || !isUsableAfterInlineStyleChange(entry, *inlineStyle)) {
m_entries.remove(it);
return { };
}
auto changedProperties = computeAndUpdateChangedProperties(entry);
return CachedMatchResult {
.unadjustedStyle = copy(entry->unadjustedStyle),
.changedProperties = WTFMove(changedProperties),
.styleToUpdate = *entry->unadjustedStyle.style
};
}
void MatchResultCache::update(CachedMatchResult& result, const RenderStyle& style)
{
result.styleToUpdate.get() = RenderStyle::clone(style);
}
void MatchResultCache::updateForFastPathInherit(const Element& element, const RenderStyle& parentStyle)
{
auto entry = m_entries.get(element);
if (!entry)
return;
entry->unadjustedStyle.style->fastPathInheritFrom(parentStyle);
}
void MatchResultCache::set(const Element& element, const UnadjustedStyle& unadjustedStyle)
{
// For now we cache match results if there is mutable inline style. This way we can avoid
// selector matching when it gets mutated again.
auto* styledElement = dynamicDowncast<StyledElement>(element);
auto* inlineStyle = styledElement ? dynamicDowncast<MutableStyleProperties>(styledElement->inlineStyle()) : nullptr;
if (inlineStyle)
m_entries.set(element, makeUniqueRef<Entry>(copy(unadjustedStyle), *inlineStyle));
else
m_entries.remove(element);
}
}
}
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