style_variables.h | Explore in Territory

// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_STYLE_STYLE_VARIABLES_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_STYLE_STYLE_VARIABLES_H_

#include <iosfwd>
#include <optional>

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/css/css_value.h"
#include "third_party/blink/renderer/core/css/css_variable_data.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_hash_map.h"
#include "third_party/blink/renderer/platform/heap/persistent.h"
#include "third_party/blink/renderer/platform/wtf/forward.h"
#include "third_party/blink/renderer/platform/wtf/hash_map.h"
#include "third_party/blink/renderer/platform/wtf/hash_set.h"
#include "third_party/blink/renderer/platform/wtf/text/atomic_string_hash.h"

namespace blink {

// Contains values for custom properties.
//
// Each custom property has "variable data" and optionally a "variable value".
//
// * Data:  A CSSVariableData that contains the tokens used for substitution.
// * Value: An optional CSSValue that may be present if the custom property
//          is registered with a non-universal syntax descriptor.
//
// Note that StyleVariables may explicitly contain a nullptr value for a given
// custom property. This is necessary to be able to mark variables that become
// invalid at computed-value time [1] as such.
//
// If StyleVariables does not contain an entry at all for a given property,
// std::nullopt is returned. This allows us to differentiate between the case
// where we want to try to find the variable elsewhere (e.g. StyleInitialData,
// in the case of std::nullopt), or return nullptr without looking further.
//
// Due to the subtleties introduced by the root-bucket optimization in
// StyleInheritedVariables, there is deliberately no way to erase an entry
// from StyleVariables. This means that non-implicit initial/inherited values
// must be explicitly stored.
//
// [1] https://drafts.csswg.org/css-variables/#invalid-at-computed-value-time
class CORE_EXPORT StyleVariables { … };

CORE_EXPORT std::ostream& operator<<(std::ostream& stream,
                                     const StyleVariables& variables);

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_STYLE_STYLE_VARIABLES_H_
chromium/third_party/blink/renderer/core/style/style_variables.h
