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// Copyright 2016 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 NGBreakToken_h
#define NGBreakToken_h
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/layout/ng/ng_layout_input_node.h"
#include "third_party/blink/renderer/platform/wtf/ref_counted.h"
namespace blink {
// A break token is a continuation token for layout. A single layout input node
// can have multiple fragments asssociated with it.
//
// Each fragment has a break token which can be used to determine if a layout
// input node has finished producing fragments (aka. is "exhausted" of
// fragments), and optionally used to produce the next fragment in the chain.
//
// See CSS Fragmentation (https://drafts.csswg.org/css-break/) for a detailed
// description of different types of breaks which can occur in CSS.
//
// Each layout algorithm which can fragment, e.g. block-flow can optionally
// accept a break token. For example:
//
// NGLayoutInputNode* node = ...;
// NGPhysicalFragment* fragment = node->Layout(space);
// DCHECK(!fragment->BreakToken()->IsFinished());
// NGPhysicalFragment* fragment2 = node->Layout(space, fragment->BreakToken());
//
// The break token should encapsulate enough information to "resume" the layout.
class CORE_EXPORT NGBreakToken : public RefCounted<NGBreakToken> {
public:
virtual ~NGBreakToken() = default;
enum NGBreakTokenType { kBlockBreakToken, kInlineBreakToken };
NGBreakTokenType Type() const { return static_cast<NGBreakTokenType>(type_); }
bool IsBlockType() const { return Type() == kBlockBreakToken; }
bool IsInlineType() const { return Type() == kInlineBreakToken; }
enum NGBreakTokenStatus { kUnfinished, kFinished };
// Whether the layout node cannot produce any more fragments.
bool IsFinished() const { return status_ == kFinished; }
// Returns the node associated with this break token. A break token cannot be
// used with any other node.
NGLayoutInputNode InputNode() const { return node_; }
#ifndef NDEBUG
virtual String ToString() const;
void ShowBreakTokenTree() const;
#endif // NDEBUG
protected:
NGBreakToken(NGBreakTokenType type,
NGBreakTokenStatus status,
NGLayoutInputNode node)
: type_(type), status_(status), node_(node) {}
private:
unsigned type_ : 1;
unsigned status_ : 1;
NGLayoutInputNode node_;
};
} // namespace blink
#endif // NGBreakToken_h
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