Source/WebCore/style/HasSelectorFilter.cpp

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 * Copyright (C) 2021 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *     documentation and/or other materials provided with the distribution.
 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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#include "config.h"
#include "HasSelectorFilter.h"

#include "ElementIterator.h"
#include "RuleFeature.h"
#include "SelectorFilter.h"
#include "StyleRule.h"

namespace WebCore::Style {

// FIXME: Support additional pseudo-classes.
static constexpr unsigned HoverSalt = 101;

HasSelectorFilter::HasSelectorFilter(const Element& element, Type type)
    : m_type(type)
{
    switch (type) {
    case Type::Descendants:
        for (auto& descendant : descendantsOfType<Element>(element))
            add(descendant);
        break;
    case Type::Children:
        for (auto& child : childrenOfType<Element>(element))
            add(child);
        break;
    }
}

auto HasSelectorFilter::typeForMatchElement(MatchElement matchElement) -> std::optional<Type>
{
    switch (matchElement) {
    case MatchElement::HasChild:
        return Type::Children;
    case MatchElement::HasDescendant:
        return Type::Descendants;
    default:
        return { };
    }
}

auto HasSelectorFilter::makeKey(const CSSSelector& hasSelector) -> Key
{
    SelectorFilter::CollectedSelectorHashes hashes;
    bool hasHoverInCompound = false;
    for (auto* simpleSelector = &hasSelector; simpleSelector; simpleSelector = simpleSelector->tagHistory()) {
        if (simpleSelector->match() == CSSSelector::PseudoClass && simpleSelector->pseudoClassType() == CSSSelector::PseudoClassHover)
            hasHoverInCompound = true;
        SelectorFilter::collectSimpleSelectorHash(hashes, *simpleSelector);
        if (!hashes.ids.isEmpty())
            break;
        if (simpleSelector->relation() != CSSSelector::Subselector)
            break;
    }

    auto pickKey = [&](auto& hashVector) -> Key {
        if (hashVector.isEmpty())
            return 0;
        if (hasHoverInCompound)
            return hashVector[0] * HoverSalt;
        return hashVector[0];
    };

    if (auto key = pickKey(hashes.ids))
        return key;
    if (auto key = pickKey(hashes.classes))
        return key;
    if (auto key = pickKey(hashes.attributes))
        return key;
    return pickKey(hashes.tags);
}

void HasSelectorFilter::add(const Element& element)
{
    Vector<unsigned, 4> elementHashes;
    SelectorFilter::collectElementIdentifierHashes(element, elementHashes);

    for (auto hash : elementHashes)
        m_filter.add(hash);

    if (element.hovered()) {
        for (auto hash : elementHashes)
            m_filter.add(hash * HoverSalt);
    }
}

}