summaryrefslogtreecommitdiff
path: root/dom/base/nsLineBreaker.h
blob: 81c4c334e9bf6369e80abf30e0aa7fba959616df (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef NSLINEBREAKER_H_
#define NSLINEBREAKER_H_

#include "nsString.h"
#include "nsTArray.h"
#include "nsILineBreaker.h"

class nsIAtom;
class nsHyphenator;

/**
 * A receiver of line break data.
 */
class nsILineBreakSink {
public:
  /**
   * Sets the break data for a substring of the associated text chunk.
   * One or more of these calls will be performed; the union of all substrings
   * will cover the entire text chunk. Substrings may overlap (i.e., we may
   * set the break-before state of a character more than once).
   * @param aBreakBefore the break-before states for the characters in the substring.
   * These are enum values from gfxTextRun::CompressedGlyph:
   *    FLAG_BREAK_TYPE_NONE     - no linebreak is allowed here
   *    FLAG_BREAK_TYPE_NORMAL   - a normal (whitespace) linebreak
   *    FLAG_BREAK_TYPE_HYPHEN   - a hyphenation point
   */
  virtual void SetBreaks(uint32_t aStart, uint32_t aLength, uint8_t* aBreakBefore) = 0;
  
  /**
   * Indicates which characters should be capitalized. Only called if
   * BREAK_NEED_CAPITALIZATION was requested.
   */
  virtual void SetCapitalization(uint32_t aStart, uint32_t aLength, bool* aCapitalize) = 0;
};

/**
 * A line-breaking state machine. You feed text into it via AppendText calls
 * and it computes the possible line breaks. Because break decisions can
 * require a lot of context, the breaks for a piece of text are sometimes not
 * known until later text has been seen (or all text ends). So breaks are
 * returned via a call to SetBreaks on the nsILineBreakSink object passed
 * with each text chunk, which might happen during the corresponding AppendText
 * call, or might happen during a later AppendText call or even a Reset()
 * call.
 * 
 * The linebreak results MUST NOT depend on how the text is broken up
 * into AppendText calls.
 * 
 * The current strategy is that we break the overall text into
 * whitespace-delimited "words". Then those words are passed to the nsILineBreaker
 * service for deeper analysis if they contain a "complex" character as described
 * below.
 * 
 * This class also handles detection of which characters should be capitalized
 * for text-transform:capitalize. This is a good place to handle that because
 * we have all the context we need.
 */
class nsLineBreaker {
public:
  nsLineBreaker();
  ~nsLineBreaker();
  
  static inline bool IsSpace(char16_t u) { return NS_IsSpace(u); }

  static inline bool IsComplexASCIIChar(char16_t u)
  {
    return !((0x0030 <= u && u <= 0x0039) ||
             (0x0041 <= u && u <= 0x005A) ||
             (0x0061 <= u && u <= 0x007A) ||
             (0x000a == u));
  }

  static inline bool IsComplexChar(char16_t u)
  {
    return IsComplexASCIIChar(u) ||
           NS_NeedsPlatformNativeHandling(u) ||
           (0x1100 <= u && u <= 0x11ff) || // Hangul Jamo
           (0x2000 <= u && u <= 0x21ff) || // Punctuations and Symbols
           (0x2e80 <= u && u <= 0xd7ff) || // several CJK blocks
           (0xf900 <= u && u <= 0xfaff) || // CJK Compatibility Idographs
           (0xff00 <= u && u <= 0xffef);   // Halfwidth and Fullwidth Forms
  }

  // Break opportunities exist at the end of each run of breakable whitespace
  // (see IsSpace above). Break opportunities can also exist between pairs of
  // non-whitespace characters, as determined by nsILineBreaker. We pass a whitespace-
  // delimited word to nsILineBreaker if it contains at least one character
  // matching IsComplexChar.
  // We provide flags to control on a per-chunk basis where breaks are allowed.
  // At any character boundary, exactly one text chunk governs whether a
  // break is allowed at that boundary.
  //
  // We operate on text after whitespace processing has been applied, so
  // other characters (e.g. tabs and newlines) may have been converted to
  // spaces.

  /**
   * Flags passed with each chunk of text.
   */
  enum {
    /*
     * Do not introduce a break opportunity at the start of this chunk of text.
     */
    BREAK_SUPPRESS_INITIAL = 0x01,
    /**
     * Do not introduce a break opportunity in the interior of this chunk of text.
     * Also, whitespace in this chunk is treated as non-breakable.
     */
    BREAK_SUPPRESS_INSIDE = 0x02,
    /**
     * The sink currently is already set up to have no breaks in it;
     * if no breaks are possible, nsLineBreaker does not need to call
     * SetBreaks on it. This is useful when handling large quantities of
     * preformatted text; the textruns will never have any breaks set on them,
     * and there is no need to ever actually scan the text for breaks, except
     * at the end of textruns in case context is needed for following breakable
     * text.
     */
    BREAK_SKIP_SETTING_NO_BREAKS = 0x04,
    /**
     * We need to be notified of characters that should be capitalized
     * (as in text-transform:capitalize) in this chunk of text.
     */
    BREAK_NEED_CAPITALIZATION = 0x08,
    /**
     * Auto-hyphenation is enabled, so we need to get a hyphenator
     * (if available) and use it to find breakpoints.
     */
    BREAK_USE_AUTO_HYPHENATION = 0x10
  };

  /**
   * Append "invisible whitespace". This acts like whitespace, but there is
   * no actual text associated with it. Only the BREAK_SUPPRESS_INSIDE flag
   * is relevant here.
   */
  nsresult AppendInvisibleWhitespace(uint32_t aFlags);

  /**
   * Feed Unicode text into the linebreaker for analysis. aLength must be
   * nonzero.
   * @param aSink can be null if the breaks are not actually needed (we may
   * still be setting up state for later breaks)
   */
  nsresult AppendText(nsIAtom* aHyphenationLanguage, const char16_t* aText, uint32_t aLength,
                      uint32_t aFlags, nsILineBreakSink* aSink);
  /**
   * Feed 8-bit text into the linebreaker for analysis. aLength must be nonzero.
   * @param aSink can be null if the breaks are not actually needed (we may
   * still be setting up state for later breaks)
   */
  nsresult AppendText(nsIAtom* aHyphenationLanguage, const uint8_t* aText, uint32_t aLength,
                      uint32_t aFlags, nsILineBreakSink* aSink);
  /**
   * Reset all state. This means the current run has ended; any outstanding
   * calls through nsILineBreakSink are made, and all outstanding references to
   * nsILineBreakSink objects are dropped.
   * After this call, this linebreaker can be reused.
   * This must be called at least once between any call to AppendText() and
   * destroying the object.
   * @param aTrailingBreak this is set to true when there is a break opportunity
   * at the end of the text. This will normally only be declared true when there
   * is breakable whitespace at the end.
   */
  nsresult Reset(bool* aTrailingBreak);

  /*
   * Set word-break mode for linebreaker.  This is set by word-break property.
   * @param aMode is nsILineBreaker::kWordBreak_* value.
   */
  void SetWordBreak(uint8_t aMode) { mWordBreak = aMode; }

private:
  // This is a list of text sources that make up the "current word" (i.e.,
  // run of text which does not contain any whitespace). All the mLengths
  // are are nonzero, these cannot overlap.
  struct TextItem {
    TextItem(nsILineBreakSink* aSink, uint32_t aSinkOffset, uint32_t aLength,
             uint32_t aFlags)
      : mSink(aSink), mSinkOffset(aSinkOffset), mLength(aLength), mFlags(aFlags) {}

    nsILineBreakSink* mSink;
    uint32_t          mSinkOffset;
    uint32_t          mLength;
    uint32_t          mFlags;
  };

  // State for the nonwhitespace "word" that started in previous text and hasn't
  // finished yet.

  // When the current word ends, this computes the linebreak opportunities
  // *inside* the word (excluding either end) and sets them through the
  // appropriate sink(s). Then we clear the current word state.
  nsresult FlushCurrentWord();

  void UpdateCurrentWordLanguage(nsIAtom *aHyphenationLanguage);

  void FindHyphenationPoints(nsHyphenator *aHyphenator,
                             const char16_t *aTextStart,
                             const char16_t *aTextLimit,
                             uint8_t *aBreakState);

  AutoTArray<char16_t,100> mCurrentWord;
  // All the items that contribute to mCurrentWord
  AutoTArray<TextItem,2>    mTextItems;
  nsIAtom*                    mCurrentWordLanguage;
  bool                        mCurrentWordContainsMixedLang;
  bool                        mCurrentWordContainsComplexChar;

  // True if the previous character was breakable whitespace
  bool                        mAfterBreakableSpace;
  // True if a break must be allowed at the current position because
  // a run of breakable whitespace ends here
  bool                        mBreakHere;
  // line break mode by "word-break" style
  uint8_t                     mWordBreak;
};

#endif /*NSLINEBREAKER_H_*/