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
32 namespace blink {
33
34 enum BidiEmbeddingSource {
35 FromStyleOrDOM,
36 FromUnicode
37 };
38
39 // Used to keep track of explicit embeddings.
40 class PLATFORM_EXPORT BidiContext : public RefCounted<BidiContext> {
41 public:
42 static PassRefPtr<BidiContext> create(unsigned char level, WTF::Unicode::Direction, bool override = false, BidiEmbeddingSource = FromStyleOrDOM, BidiContext* parent = 0);
43
parent()44 BidiContext* parent() const { return m_parent.get(); }
level()45 unsigned char level() const { return m_level; }
dir()46 WTF::Unicode::Direction dir() const { return static_cast<WTF::Unicode::Direction>(m_direction); }
override()47 bool override() const { return m_override; }
source()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
57 private:
BidiContext(unsigned char level,WTF::Unicode::Direction direction,bool override,BidiEmbeddingSource source,BidiContext * parent)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
nextGreaterOddLevel(unsigned char level)77 inline unsigned char nextGreaterOddLevel(unsigned char level)
78 {
79 return (level + 1) | 1;
80 }
81
nextGreaterEvenLevel(unsigned char level)82 inline unsigned char nextGreaterEvenLevel(unsigned char level)
83 {
84 return (level + 2) & ~1;
85 }
86
87 PLATFORM_EXPORT bool operator==(const BidiContext&, const BidiContext&);
88
89 } // namespace blink
90
91 #endif // BidiContext_h
92