Source/WebCore/style/ClassChangeInvalidation.cpp

/*
 * Copyright (C) 2016 Apple Inc. All rights reserved.
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#include "config.h"
#include "ClassChangeInvalidation.h"

#include "ElementChildIterator.h"
#include "ElementRareData.h"
#include "SpaceSplitString.h"
#include "StyleInvalidationFunctions.h"
#include <wtf/BitVector.h>

namespace WebCore {
namespace Style {

enum class ClassChangeType : bool { Add, Remove };

struct ClassChange {
    AtomStringImpl* className { };
    ClassChangeType type;
};

using ClassChangeVector = Vector<ClassChange, 4>;

static ClassChangeVector collectClasses(const SpaceSplitString& classes, ClassChangeType changeType)
{
    ClassChangeVector result;
    result.reserveInitialCapacity(classes.size());
    for (unsigned i = 0; i < classes.size(); ++i)
        result.uncheckedAppend({ classes[i].impl(), changeType });
    return result;
}

static ClassChangeVector computeClassChanges(const SpaceSplitString& oldClasses, const SpaceSplitString& newClasses)
{
    unsigned oldSize = oldClasses.size();
    unsigned newSize = newClasses.size();

    if (!oldSize)
        return collectClasses(newClasses, ClassChangeType::Add);
    if (!newSize)
        return collectClasses(oldClasses, ClassChangeType::Remove);

    ClassChangeVector changedClasses;

    BitVector remainingClassBits;
    remainingClassBits.ensureSize(oldSize);
    // Class vectors tend to be very short. This is faster than using a hash table.
    for (unsigned i = 0; i < newSize; ++i) {
        bool foundFromBoth = false;
        for (unsigned j = 0; j < oldSize; ++j) {
            if (newClasses[i] == oldClasses[j]) {
                remainingClassBits.quickSet(j);
                foundFromBoth = true;
            }
        }
        if (foundFromBoth)
            continue;
        changedClasses.append({ newClasses[i].impl(), ClassChangeType::Add });
    }
    for (unsigned i = 0; i < oldSize; ++i) {
        // If the bit is not set the corresponding class has been removed.
        if (remainingClassBits.quickGet(i))
            continue;
        changedClasses.append({ oldClasses[i].impl(), ClassChangeType::Remove });
    }

    return changedClasses;
}

void ClassChangeInvalidation::computeInvalidation(const SpaceSplitString& oldClasses, const SpaceSplitString& newClasses)
{
    auto classChanges = computeClassChanges(oldClasses, newClasses);

    bool shouldInvalidateCurrent = false;
    bool mayAffectStyleInShadowTree = false;

    traverseRuleFeatures(m_element, [&] (const RuleFeatureSet& features, bool mayAffectShadowTree) {
        for (auto& classChange : classChanges) {
            if (mayAffectShadowTree && features.classRules.contains(classChange.className))
                mayAffectStyleInShadowTree = true;
            if (features.classesAffectingHost.contains(classChange.className))
                shouldInvalidateCurrent = true;
        }
    });

    if (mayAffectStyleInShadowTree) {
        // FIXME: We should do fine-grained invalidation for shadow tree.
        m_element.invalidateStyleForSubtree();
    }

    if (shouldInvalidateCurrent)
        m_element.invalidateStyle();

    auto& ruleSets = m_element.styleResolver().ruleSets();

    auto invalidateBeforeChange = [](ClassChangeType type, IsNegation isNegation) {
        if (type == ClassChangeType::Remove)
            return isNegation == IsNegation::No;
        return isNegation == IsNegation::Yes;
    };

    for (auto& classChange : classChanges) {
        if (auto* invalidationRuleSets = ruleSets.classInvalidationRuleSets(classChange.className)) {
            for (auto& invalidationRuleSet : *invalidationRuleSets) {
                if (invalidateBeforeChange(classChange.type, invalidationRuleSet.isNegation))
                    Invalidator::addToMatchElementRuleSets(m_beforeChangeRuleSets, invalidationRuleSet);
                else
                    Invalidator::addToMatchElementRuleSets(m_afterChangeRuleSets, invalidationRuleSet);
            }
        }
    }
}

void ClassChangeInvalidation::invalidateBeforeChange()
{
    Invalidator::invalidateWithMatchElementRuleSets(m_element, m_beforeChangeRuleSets);
}

void ClassChangeInvalidation::invalidateAfterChange()
{
    Invalidator::invalidateWithMatchElementRuleSets(m_element, m_afterChangeRuleSets);
}

}
}