third_party/WebKit/Source/platform/text/BidiContext.h

/*
 * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
 * Copyright (C) 2003, 2004, 2006, 2007, 2009, 2010 Apple Inc.
 * All right reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#ifndef BidiContext_h
#define BidiContext_h

#include "platform/PlatformExport.h"
#include "wtf/Assertions.h"
#include "wtf/PassRefPtr.h"
#include "wtf/RefCounted.h"
#include "wtf/RefPtr.h"
#include "wtf/text/Unicode.h"

namespace blink {

enum BidiEmbeddingSource { FromStyleOrDOM, FromUnicode };

// Used to keep track of explicit embeddings.
class PLATFORM_EXPORT BidiContext : public RefCounted<BidiContext> {
 public:
  static PassRefPtr<BidiContext> create(unsigned char level,
                                        WTF::Unicode::CharDirection,
                                        bool override = false,
                                        BidiEmbeddingSource = FromStyleOrDOM,
                                        BidiContext* parent = 0);

  BidiContext* parent() const { return m_parent.get(); }
  unsigned char level() const { return m_level; }
  WTF::Unicode::CharDirection dir() const {
    return static_cast<WTF::Unicode::CharDirection>(m_direction);
  }
  bool override() const { return m_override; }
  BidiEmbeddingSource source() const {
    return static_cast<BidiEmbeddingSource>(m_source);
  }

  PassRefPtr<BidiContext> copyStackRemovingUnicodeEmbeddingContexts();

  // http://www.unicode.org/reports/tr9/#Modifications
  // 6.3 raised the limit from 61 to 125.
  // http://unicode.org/reports/tr9/#BD2
  static const unsigned char kMaxLevel = 125;

 private:
  BidiContext(unsigned char level,
              WTF::Unicode::CharDirection direction,
              bool override,
              BidiEmbeddingSource source,
              BidiContext* parent)
      : m_level(level),
        m_direction(direction),
        m_override(override),
        m_source(source),
        m_parent(parent) {
    ASSERT(level <= kMaxLevel);
  }

  static PassRefPtr<BidiContext> createUncached(unsigned char level,
                                                WTF::Unicode::CharDirection,
                                                bool override,
                                                BidiEmbeddingSource,
                                                BidiContext* parent);

  // The maximium bidi level is 125:
  // http://unicode.org/reports/tr9/#Explicit_Levels_and_Directions
  unsigned m_level : 7;
  unsigned m_direction : 5;  // Direction
  unsigned m_override : 1;
  unsigned m_source : 1;  // BidiEmbeddingSource
  RefPtr<BidiContext> m_parent;
};

inline unsigned char nextGreaterOddLevel(unsigned char level) {
  return (level + 1) | 1;
}

inline unsigned char nextGreaterEvenLevel(unsigned char level) {
  return (level + 2) & ~1;
}

PLATFORM_EXPORT bool operator==(const BidiContext&, const BidiContext&);

}  // namespace blink

#endif  // BidiContext_h