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// Copyright 2021 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_CSS_CASCADE_LAYER_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CASCADE_LAYER_H_
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/css/style_rule.h"
#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
#include "third_party/blink/renderer/platform/wtf/hash_set.h"
#include "third_party/blink/renderer/platform/wtf/text/atomic_string.h"
namespace blink {
// Mapping from one layer to another (obviously). This is used in two places:
//
// - When building superrulesets, we merge the RuleSets' layers
// to new CascadeLayer objects in the superruleset. Normally,
// we also map values in the RuleSet::Intervals, but occasionally,
// we need to look up @page rule etc. in the original RuleSets
// (which are not mapped), so we need to also be able to look up
// by the old layers, so we store and use the mapping.
//
// - When building CascadeLayerMap (cascade_layer_map.h), we similarly combine
// layers from all active RuleSets (the superruleset's layers
// will be used in place of the layers of all RuleSets it is
// subsuming), into one grouping so give them a canonical numbering.
// For clarity, we use the typedef CanonicalLayerMap there.
using LayerMap = HeapHashMap<Member<const CascadeLayer>, Member<CascadeLayer>>;
// A CascadeLayer object represents a node in the ordered tree of cascade layers
// in the sorted layer ordering.
// https://www.w3.org/TR/css-cascade-5/#layer-ordering
class CORE_EXPORT CascadeLayer final : public GarbageCollected<CascadeLayer> {
public:
explicit CascadeLayer(const AtomicString& name = g_empty_atom)
: name_(name) {}
~CascadeLayer() = default;
const AtomicString& GetName() const { return name_; }
const HeapVector<Member<CascadeLayer>>& GetDirectSubLayers() const {
return direct_sub_layers_;
}
// Getting or setting the order of a layer is only valid for canonical cascade
// layers i.e. the unique layer representation for a particular tree scope.
const std::optional<uint16_t> GetOrder() const { return order_; }
void SetOrder(uint16_t order) { order_ = order; }
CascadeLayer* GetOrAddSubLayer(const StyleRuleBase::LayerName& name);
// Recursive merge, used during creation of superrulesets.
// The hash set gets filled/appended with a map from the old to the new
// layers, where applicable (no sub-CascadeLayer objects from “other”
// are ever reused, so that they are unchanged even after future merges).
//
// This merges only the sub-layer structure and creates the mapping;
// it does not touch order_, which is updated during creation of the
// CascadeLayerMap.
void Merge(const CascadeLayer& other, LayerMap& mapping);
void Trace(blink::Visitor*) const;
private:
friend class CascadeLayerTest;
friend class RuleSetCascadeLayerTest;
String ToStringForTesting() const;
void ToStringInternal(StringBuilder&, const String&) const;
CascadeLayer* FindDirectSubLayer(const AtomicString&) const;
void ComputeLayerOrderInternal(unsigned* next);
std::optional<uint16_t> order_;
AtomicString name_;
HeapVector<Member<CascadeLayer>> direct_sub_layers_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CASCADE_LAYER_H_
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