Source/WebCore/css/CSSVariableReferenceValue.h

// Copyright 2015 The Chromium Authors. All rights reserved.
// Copyright (C) 2016-2021 Apple Inc. All rights reserved.
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#pragma once

#include <WebCore/CSSParserTokenRange.h>
#include <WebCore/CSSPropertyNames.h>
#include <WebCore/CSSValue.h>
#include <WebCore/CSSValueKeywords.h>
#include <WebCore/CSSVariableData.h>
#include <wtf/PointerComparison.h>
#include <wtf/text/WTFString.h>

namespace WebCore {

class CSSParserToken;
struct CSSParserContext;

namespace Style {
class Builder;
}

enum CSSPropertyID : uint16_t;

class CSSVariableReferenceValue final : public CSSValue {
public:
    static Ref<CSSVariableReferenceValue> create(const CSSParserTokenRange&, const CSSParserContext&);
    static Ref<CSSVariableReferenceValue> create(Ref<CSSVariableData>&&);

    bool equals(const CSSVariableReferenceValue&) const;
    String customCSSText(const CSS::SerializationContext&) const;

    RefPtr<CSSVariableData> resolveVariableReferences(Style::Builder&) const;
    const CSSParserContext& context() const;

    RefPtr<CSSValue> resolveSingleValue(Style::Builder&, CSSPropertyID) const;

    // The maximum number of tokens that may be produced by a var() reference or var() fallback value.
    // https://drafts.csswg.org/css-variables/#long-variables
    static constexpr size_t maxSubstitutionTokens = 65536;
    
    const CSSVariableData& data() const { return m_data.get(); }

    template<typename CacheFunction> bool resolveAndCacheValue(Style::Builder&, NOESCAPE const CacheFunction&) const;

private:
    explicit CSSVariableReferenceValue(Ref<CSSVariableData>&&);

    std::optional<Vector<CSSParserToken>> resolveTokenRange(CSSParserTokenRange, Style::Builder&) const;
    bool resolveVariableReference(CSSParserTokenRange, CSSValueID, Vector<CSSParserToken>&, Style::Builder&) const;
    bool evaluateDashedFunction(StringView functionName, CSSParserTokenRange, Vector<CSSParserToken>&, Style::Builder&) const;

    enum class FallbackResult : uint8_t { None, Valid, Invalid };
    std::pair<FallbackResult, Vector<CSSParserToken>> resolveVariableFallback(const AtomString& variableName, CSSParserTokenRange, CSSValueID functionId, Style::Builder&) const;

    void cacheSimpleReference();
    RefPtr<CSSVariableData> tryResolveSimpleReference(Style::Builder&) const;

    const Ref<CSSVariableData> m_data;
    mutable String m_stringValue;

    // For quicky resolving simple var(--foo) values.
    struct SimpleReference {
        AtomString name;
        CSSValueID functionId;
    };
    std::optional<SimpleReference> m_simpleReference;

    mutable RefPtr<CSSVariableData> m_cacheDependencyData;
    mutable RefPtr<CSSValue> m_cachedValue;
#if ASSERT_ENABLED
    mutable CSSPropertyID m_cachePropertyID { CSSPropertyInvalid };
#endif
};

template<typename CacheFunction>
bool CSSVariableReferenceValue::resolveAndCacheValue(Style::Builder& builder, NOESCAPE const CacheFunction& cacheFunction) const

{
    if (auto data = tryResolveSimpleReference(builder)) {
        if (!arePointingToEqualData(m_cacheDependencyData, data))
            cacheFunction(data);
        m_cacheDependencyData = WTF::move(data);
        return true;
    }

    auto resolvedTokens = resolveTokenRange(m_data->tokenRange(), builder);
    if (!resolvedTokens)
        return false;

    if (!m_cacheDependencyData || m_cacheDependencyData->tokens() != *resolvedTokens) {
        m_cacheDependencyData = CSSVariableData::create(*resolvedTokens, context());
        cacheFunction(m_cacheDependencyData);
    }
    return true;
}

} // namespace WebCore

SPECIALIZE_TYPE_TRAITS_CSS_VALUE(CSSVariableReferenceValue, isVariableReferenceValue())