1/*
2 * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
3 * Copyright (C) 2003, 2004, 2006, 2007, 2009, 2010 Apple Inc. All right reserved.
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Library General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13 * Library General Public License for more details.
14 *
15 * You should have received a copy of the GNU Library General Public License
16 * along with this library; see the file COPYING.LIB.  If not, write to
17 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
18 * Boston, MA 02110-1301, USA.
19 *
20 */
21
22#ifndef BidiContext_h
23#define BidiContext_h
24
25#include "platform/PlatformExport.h"
26#include "wtf/Assertions.h"
27#include "wtf/PassRefPtr.h"
28#include "wtf/RefCounted.h"
29#include "wtf/RefPtr.h"
30#include "wtf/unicode/Unicode.h"
31
32namespace blink {
33
34enum BidiEmbeddingSource {
35    FromStyleOrDOM,
36    FromUnicode
37};
38
39// Used to keep track of explicit embeddings.
40class PLATFORM_EXPORT BidiContext : public RefCounted<BidiContext> {
41public:
42    static PassRefPtr<BidiContext> create(unsigned char level, WTF::Unicode::Direction, bool override = false, BidiEmbeddingSource = FromStyleOrDOM, BidiContext* parent = 0);
43
44    BidiContext* parent() const { return m_parent.get(); }
45    unsigned char level() const { return m_level; }
46    WTF::Unicode::Direction dir() const { return static_cast<WTF::Unicode::Direction>(m_direction); }
47    bool override() const { return m_override; }
48    BidiEmbeddingSource source() const { return static_cast<BidiEmbeddingSource>(m_source); }
49
50    PassRefPtr<BidiContext> copyStackRemovingUnicodeEmbeddingContexts();
51
52    // http://www.unicode.org/reports/tr9/#Modifications
53    // 6.3 raised the limit from 61 to 125.
54    // http://unicode.org/reports/tr9/#BD2
55    static const unsigned char kMaxLevel = 125;
56
57private:
58    BidiContext(unsigned char level, WTF::Unicode::Direction direction, bool override, BidiEmbeddingSource source, BidiContext* parent)
59        : m_level(level)
60        , m_direction(direction)
61        , m_override(override)
62        , m_source(source)
63        , m_parent(parent)
64    {
65        ASSERT(level <= kMaxLevel);
66    }
67
68    static PassRefPtr<BidiContext> createUncached(unsigned char level, WTF::Unicode::Direction, bool override, BidiEmbeddingSource, BidiContext* parent);
69
70    unsigned m_level : 7; // The maximium bidi level is 125: http://unicode.org/reports/tr9/#Explicit_Levels_and_Directions
71    unsigned m_direction : 5; // Direction
72    unsigned m_override : 1;
73    unsigned m_source : 1; // BidiEmbeddingSource
74    RefPtr<BidiContext> m_parent;
75};
76
77inline unsigned char nextGreaterOddLevel(unsigned char level)
78{
79    return (level + 1) | 1;
80}
81
82inline unsigned char nextGreaterEvenLevel(unsigned char level)
83{
84    return (level + 2) & ~1;
85}
86
87PLATFORM_EXPORT bool operator==(const BidiContext&, const BidiContext&);
88
89} // namespace blink
90
91#endif // BidiContext_h
92