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// Copyright 2020 The Chromium Authors. All rights reserved.
// 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_CSS_RESOLVER_CASCADE_EXPANSION_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_RESOLVER_CASCADE_EXPANSION_H_
#include <limits>
#include "third_party/blink/renderer/core/css/properties/longhands/custom_property.h"
#include "third_party/blink/renderer/core/css/resolver/cascade_filter.h"
#include "third_party/blink/renderer/core/css/resolver/cascade_origin.h"
#include "third_party/blink/renderer/core/css/resolver/cascade_priority.h"
#include "third_party/blink/renderer/core/style/computed_style_base_constants.h"
namespace blink {
struct MatchedProperties;
inline uint32_t EncodeMatchResultPosition(uint16_t block,
uint16_t declaration) {
return (static_cast<uint32_t>(block) << 16) | declaration;
}
inline size_t DecodeMatchedPropertiesIndex(uint32_t position) {
return (position >> 16) & 0xFFFF;
}
inline size_t DecodeDeclarationIndex(uint32_t position) {
return position & 0xFFFF;
}
// CascadeExpansion takes a declaration block (MatchedProperties) and
// expands the declarations found into the final list of declarations observed
// by StyleCascade. It exists to prevent callers to deal with the complexity
// of the 'all' property, '-internal-visited-' properties, '-internal-ua-'
// properties, and filtering of both regular declarations and "generated"
// declarations.
//
// For example, for the declaration block:
//
// top:1px;
// all:unset;
// top:2px;
//
// CascadeExpansion would emit:
//
// top:1px;
// animation-delay:unset;
// animation-direction:unset;
// /* ... <all longhands affected by 'all'> ... */
// -webkit-text-emphasis:unset;
// -webkit-text-stroke:unset;
// top:2px;
//
// In other words, 'all' is expanded into the actual longhands it represents.
// A similar expansion happens for properties which have companion
// -internal-visited-* properties (depending on inside-link status).
//
// Usage:
//
// CascadeExpansion e = ...;
// for (; !e.AtEnd(); a.Next())
// DoStuff(e);
//
class CORE_EXPORT CascadeExpansion {
STACK_ALLOCATED();
enum class State { kInit, kNormal, kVisited, kAll };
public:
// CascadeExpansion objects which exceed these limits will emit nothing.
static constexpr size_t kMaxDeclarationIndex =
std::numeric_limits<uint16_t>::max();
static constexpr size_t kMaxMatchedPropertiesIndex =
std::numeric_limits<uint16_t>::max();
CascadeExpansion(const MatchedProperties&,
const Document&,
CascadeFilter,
size_t matched_properties_index);
// We need an explicit copy constructor, since CascadeExpansion has self-
// pointers.
CascadeExpansion(const CascadeExpansion& o);
void Next();
inline bool AtEnd() const { return index_ >= size_; }
inline CSSPropertyID Id() const { return id_; }
inline CSSPropertyName Name() const {
if (id_ != CSSPropertyID::kVariable)
return CSSPropertyName(id_);
return Property().GetCSSPropertyName();
}
inline const CSSProperty& Property() const {
DCHECK(!AtEnd());
return *property_;
}
inline const CSSValue& Value() const {
DCHECK(!AtEnd());
return PropertyAt(index_).Value();
}
inline CascadePriority Priority() const { return priority_; }
uint16_t TreeOrder() const;
private:
friend class CascadeExpansionTest;
static bool IsInAllExpansion(CSSPropertyID);
bool ShouldEmitVisited() const;
void AdvanceNormal();
bool AdvanceVisited();
void AdvanceAll();
CSSPropertyValueSet::PropertyReference PropertyAt(size_t) const;
const Document& document_;
State state_ = State::kInit;
const MatchedProperties& matched_properties_;
// The priority of the current declaration pointed to by index_. This does
// not change for generated declarations.
CascadePriority priority_;
// Index and size of the regular declarations. In other words, index_ will
// only move during State::kNormal, and not while expanding 'all', etc. It
// will always point to a valid index in matched_properties_ (unless we're
// AtEnd()).
//
// Note that this is initialized to ~0 such that the first call to Next()
// (done by the constructor) will produce ~0+1 = 0.
size_t index_ = std::numeric_limits<size_t>::max();
size_t size_;
CascadeFilter filter_;
const size_t matched_properties_index_;
// The id/property of the current "virtual" declaration. In other words,
// the id/property will be updated when expanding 'all', etc.
CSSPropertyID id_ = CSSPropertyID::kInvalid;
const CSSProperty* property_ = nullptr;
CustomProperty custom_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_RESOLVER_CASCADE_EXPANSION_H_
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