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// Copyright 2019 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_LAYOUT_NG_CUSTOM_CUSTOM_LAYOUT_SCOPE_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_NG_CUSTOM_CUSTOM_LAYOUT_SCOPE_H_
#include "third_party/blink/renderer/core/layout/ng/custom/custom_layout_work_task.h"
#include "third_party/blink/renderer/platform/heap/handle.h"
namespace blink {
// The work queue is a list of work tasks which will either produce fragment(s)
// or intrinsic-size(s) for the custom-layout class.
typedef Vector<CustomLayoutWorkTask, 4> CustomLayoutWorkQueue;
// This heap allocated class is used to indicate which custom-layout (heap)
// objects are still valid.
//
// Any objects which have a pointer to this object with |is_detached_| being
// true, or not matching the current scope token should be considered invalid.
class CustomLayoutToken : public GarbageCollected<CustomLayoutToken> {
public:
CustomLayoutToken() : is_detached_(false) {}
void Trace(Visitor* visitor) {}
bool IsValid() const;
private:
friend class CustomLayoutScope;
bool is_detached_;
};
// This scope object is used to track which custom-layout (heap) objects are
// valid.
//
// Also maintains the current work queue. Work should only be pushed onto this
// queue if this is the current scope.
class CustomLayoutScope {
STACK_ALLOCATED();
public:
static CustomLayoutScope* Current() { return current_scope_; }
CustomLayoutScope()
: prev_scope_(current_scope_),
token_(MakeGarbageCollected<CustomLayoutToken>()) {
current_scope_ = this;
}
// Marks the scope-token as "detached" for any classes with a pointer to it.
~CustomLayoutScope() {
token_->is_detached_ = true;
current_scope_ = current_scope_->prev_scope_;
}
CustomLayoutWorkQueue* Queue() {
DCHECK_EQ(this, current_scope_);
return &queue_;
}
CustomLayoutToken* Token() { return token_; }
private:
static CustomLayoutScope* current_scope_;
CustomLayoutScope* prev_scope_;
CustomLayoutWorkQueue queue_;
CustomLayoutToken* token_;
};
inline bool CustomLayoutToken::IsValid() const {
return !is_detached_ && this == CustomLayoutScope::Current()->Token();
}
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_NG_CUSTOM_CUSTOM_LAYOUT_SCOPE_H_
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