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1 /*
2  * Copyright © 1998-2004  David Turner and Werner Lemberg
3  * Copyright © 2004,2007,2009  Red Hat, Inc.
4  * Copyright © 2011,2012  Google, Inc.
5  *
6  *  This is part of HarfBuzz, a text shaping library.
7  *
8  * Permission is hereby granted, without written agreement and without
9  * license or royalty fees, to use, copy, modify, and distribute this
10  * software and its documentation for any purpose, provided that the
11  * above copyright notice and the following two paragraphs appear in
12  * all copies of this software.
13  *
14  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
15  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
16  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
17  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
18  * DAMAGE.
19  *
20  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
21  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
22  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
23  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
24  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
25  *
26  * Red Hat Author(s): Owen Taylor, Behdad Esfahbod
27  * Google Author(s): Behdad Esfahbod
28  */
29 
30 #ifndef HB_H_IN
31 #error "Include <hb.h> instead."
32 #endif
33 
34 #ifndef HB_BUFFER_H
35 #define HB_BUFFER_H
36 
37 #include "hb-common.h"
38 #include "hb-unicode.h"
39 #include "hb-font.h"
40 
41 HB_BEGIN_DECLS
42 
43 /**
44  * hb_glyph_info_t:
45  * @codepoint: either a Unicode code point (before shaping) or a glyph index
46  *             (after shaping).
47  * @cluster: the index of the character in the original text that corresponds
48  *           to this #hb_glyph_info_t, or whatever the client passes to
49  *           hb_buffer_add(). More than one #hb_glyph_info_t can have the same
50  *           @cluster value, if they resulted from the same character (e.g. one
51  *           to many glyph substitution), and when more than one character gets
52  *           merged in the same glyph (e.g. many to one glyph substitution) the
53  *           #hb_glyph_info_t will have the smallest cluster value of them.
54  *           By default some characters are merged into the same cluster
55  *           (e.g. combining marks have the same cluster as their bases)
56  *           even if they are separate glyphs, hb_buffer_set_cluster_level()
57  *           allow selecting more fine-grained cluster handling.
58  *
59  * The #hb_glyph_info_t is the structure that holds information about the
60  * glyphs and their relation to input text.
61  */
62 typedef struct hb_glyph_info_t
63 {
64   hb_codepoint_t codepoint;
65   /*< private >*/
66   hb_mask_t      mask;
67   /*< public >*/
68   uint32_t       cluster;
69 
70   /*< private >*/
71   hb_var_int_t   var1;
72   hb_var_int_t   var2;
73 } hb_glyph_info_t;
74 
75 /**
76  * hb_glyph_flags_t:
77  * @HB_GLYPH_FLAG_UNSAFE_TO_BREAK: Indicates that if input text is broken at the
78  * 				   beginning of the cluster this glyph is part of,
79  * 				   then both sides need to be re-shaped, as the
80  * 				   result might be different.  On the flip side,
81  * 				   it means that when this flag is not present,
82  * 				   then it's safe to break the glyph-run at the
83  * 				   beginning of this cluster, and the two sides
84  * 				   represent the exact same result one would get
85  * 				   if breaking input text at the beginning of
86  * 				   this cluster and shaping the two sides
87  * 				   separately.  This can be used to optimize
88  * 				   paragraph layout, by avoiding re-shaping
89  * 				   of each line after line-breaking, or limiting
90  * 				   the reshaping to a small piece around the
91  * 				   breaking point only.
92  * @HB_GLYPH_FLAG_DEFINED: All the currently defined flags.
93  *
94  * Since: 1.5.0
95  */
96 typedef enum { /*< flags >*/
97   HB_GLYPH_FLAG_UNSAFE_TO_BREAK		= 0x00000001,
98 
99   HB_GLYPH_FLAG_DEFINED			= 0x00000001 /* OR of all defined flags */
100 } hb_glyph_flags_t;
101 
102 HB_EXTERN hb_glyph_flags_t
103 hb_glyph_info_get_glyph_flags (const hb_glyph_info_t *info);
104 
105 #define hb_glyph_info_get_glyph_flags(info) \
106 	((hb_glyph_flags_t) ((unsigned int) (info)->mask & HB_GLYPH_FLAG_DEFINED))
107 
108 
109 /**
110  * hb_glyph_position_t:
111  * @x_advance: how much the line advances after drawing this glyph when setting
112  *             text in horizontal direction.
113  * @y_advance: how much the line advances after drawing this glyph when setting
114  *             text in vertical direction.
115  * @x_offset: how much the glyph moves on the X-axis before drawing it, this
116  *            should not affect how much the line advances.
117  * @y_offset: how much the glyph moves on the Y-axis before drawing it, this
118  *            should not affect how much the line advances.
119  *
120  * The #hb_glyph_position_t is the structure that holds the positions of the
121  * glyph in both horizontal and vertical directions. All positions in
122  * #hb_glyph_position_t are relative to the current point.
123  *
124  */
125 typedef struct hb_glyph_position_t {
126   hb_position_t  x_advance;
127   hb_position_t  y_advance;
128   hb_position_t  x_offset;
129   hb_position_t  y_offset;
130 
131   /*< private >*/
132   hb_var_int_t   var;
133 } hb_glyph_position_t;
134 
135 /**
136  * hb_segment_properties_t:
137  * @direction: the #hb_direction_t of the buffer, see hb_buffer_set_direction().
138  * @script: the #hb_script_t of the buffer, see hb_buffer_set_script().
139  * @language: the #hb_language_t of the buffer, see hb_buffer_set_language().
140  *
141  * The structure that holds various text properties of an #hb_buffer_t. Can be
142  * set and retrieved using hb_buffer_set_segment_properties() and
143  * hb_buffer_get_segment_properties(), respectively.
144  */
145 typedef struct hb_segment_properties_t {
146   hb_direction_t  direction;
147   hb_script_t     script;
148   hb_language_t   language;
149   /*< private >*/
150   void           *reserved1;
151   void           *reserved2;
152 } hb_segment_properties_t;
153 
154 #define HB_SEGMENT_PROPERTIES_DEFAULT {HB_DIRECTION_INVALID, \
155 				       HB_SCRIPT_INVALID, \
156 				       HB_LANGUAGE_INVALID, \
157 				       (void *) 0, \
158 				       (void *) 0}
159 
160 HB_EXTERN hb_bool_t
161 hb_segment_properties_equal (const hb_segment_properties_t *a,
162 			     const hb_segment_properties_t *b);
163 
164 HB_EXTERN unsigned int
165 hb_segment_properties_hash (const hb_segment_properties_t *p);
166 
167 
168 
169 /**
170  * hb_buffer_t:
171  *
172  * The main structure holding the input text and its properties before shaping,
173  * and output glyphs and their information after shaping.
174  */
175 
176 typedef struct hb_buffer_t hb_buffer_t;
177 
178 HB_EXTERN hb_buffer_t *
179 hb_buffer_create (void);
180 
181 HB_EXTERN hb_buffer_t *
182 hb_buffer_get_empty (void);
183 
184 HB_EXTERN hb_buffer_t *
185 hb_buffer_reference (hb_buffer_t *buffer);
186 
187 HB_EXTERN void
188 hb_buffer_destroy (hb_buffer_t *buffer);
189 
190 HB_EXTERN hb_bool_t
191 hb_buffer_set_user_data (hb_buffer_t        *buffer,
192 			 hb_user_data_key_t *key,
193 			 void *              data,
194 			 hb_destroy_func_t   destroy,
195 			 hb_bool_t           replace);
196 
197 HB_EXTERN void *
198 hb_buffer_get_user_data (hb_buffer_t        *buffer,
199 			 hb_user_data_key_t *key);
200 
201 
202 /**
203  * hb_buffer_content_type_t:
204  * @HB_BUFFER_CONTENT_TYPE_INVALID: Initial value for new buffer.
205  * @HB_BUFFER_CONTENT_TYPE_UNICODE: The buffer contains input characters (before shaping).
206  * @HB_BUFFER_CONTENT_TYPE_GLYPHS: The buffer contains output glyphs (after shaping).
207  */
208 typedef enum {
209   HB_BUFFER_CONTENT_TYPE_INVALID = 0,
210   HB_BUFFER_CONTENT_TYPE_UNICODE,
211   HB_BUFFER_CONTENT_TYPE_GLYPHS
212 } hb_buffer_content_type_t;
213 
214 HB_EXTERN void
215 hb_buffer_set_content_type (hb_buffer_t              *buffer,
216 			    hb_buffer_content_type_t  content_type);
217 
218 HB_EXTERN hb_buffer_content_type_t
219 hb_buffer_get_content_type (hb_buffer_t *buffer);
220 
221 
222 HB_EXTERN void
223 hb_buffer_set_unicode_funcs (hb_buffer_t        *buffer,
224 			     hb_unicode_funcs_t *unicode_funcs);
225 
226 HB_EXTERN hb_unicode_funcs_t *
227 hb_buffer_get_unicode_funcs (hb_buffer_t        *buffer);
228 
229 HB_EXTERN void
230 hb_buffer_set_direction (hb_buffer_t    *buffer,
231 			 hb_direction_t  direction);
232 
233 HB_EXTERN hb_direction_t
234 hb_buffer_get_direction (hb_buffer_t *buffer);
235 
236 HB_EXTERN void
237 hb_buffer_set_script (hb_buffer_t *buffer,
238 		      hb_script_t  script);
239 
240 HB_EXTERN hb_script_t
241 hb_buffer_get_script (hb_buffer_t *buffer);
242 
243 HB_EXTERN void
244 hb_buffer_set_language (hb_buffer_t   *buffer,
245 			hb_language_t  language);
246 
247 
248 HB_EXTERN hb_language_t
249 hb_buffer_get_language (hb_buffer_t *buffer);
250 
251 HB_EXTERN void
252 hb_buffer_set_segment_properties (hb_buffer_t *buffer,
253 				  const hb_segment_properties_t *props);
254 
255 HB_EXTERN void
256 hb_buffer_get_segment_properties (hb_buffer_t *buffer,
257 				  hb_segment_properties_t *props);
258 
259 HB_EXTERN void
260 hb_buffer_guess_segment_properties (hb_buffer_t *buffer);
261 
262 
263 /**
264  * hb_buffer_flags_t:
265  * @HB_BUFFER_FLAG_DEFAULT: the default buffer flag.
266  * @HB_BUFFER_FLAG_BOT: flag indicating that special handling of the beginning
267  *                      of text paragraph can be applied to this buffer. Should usually
268  *                      be set, unless you are passing to the buffer only part
269  *                      of the text without the full context.
270  * @HB_BUFFER_FLAG_EOT: flag indicating that special handling of the end of text
271  *                      paragraph can be applied to this buffer, similar to
272  *                      @HB_BUFFER_FLAG_BOT.
273  * @HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES:
274  *                      flag indication that character with Default_Ignorable
275  *                      Unicode property should use the corresponding glyph
276  *                      from the font, instead of hiding them (done by
277  *                      replacing them with the space glyph and zeroing the
278  *                      advance width.)  This flag takes precedence over
279  *                      @HB_BUFFER_FLAG_REMOVE_DEFAULT_IGNORABLES.
280  * @HB_BUFFER_FLAG_REMOVE_DEFAULT_IGNORABLES:
281  *                      flag indication that character with Default_Ignorable
282  *                      Unicode property should be removed from glyph string
283  *                      instead of hiding them (done by replacing them with the
284  *                      space glyph and zeroing the advance width.)
285  *                      @HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES takes
286  *                      precedence over this flag. Since: 1.8.0
287  *
288  * Since: 0.9.20
289  */
290 typedef enum { /*< flags >*/
291   HB_BUFFER_FLAG_DEFAULT			= 0x00000000u,
292   HB_BUFFER_FLAG_BOT				= 0x00000001u, /* Beginning-of-text */
293   HB_BUFFER_FLAG_EOT				= 0x00000002u, /* End-of-text */
294   HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES	= 0x00000004u,
295   HB_BUFFER_FLAG_REMOVE_DEFAULT_IGNORABLES	= 0x00000008u
296 } hb_buffer_flags_t;
297 
298 HB_EXTERN void
299 hb_buffer_set_flags (hb_buffer_t       *buffer,
300 		     hb_buffer_flags_t  flags);
301 
302 HB_EXTERN hb_buffer_flags_t
303 hb_buffer_get_flags (hb_buffer_t *buffer);
304 
305 /**
306  * hb_buffer_cluster_level_t:
307  * @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES: Return cluster values grouped by graphemes into
308  *   monotone order.
309  * @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS: Return cluster values grouped into monotone order.
310  * @HB_BUFFER_CLUSTER_LEVEL_CHARACTERS: Don't group cluster values.
311  * @HB_BUFFER_CLUSTER_LEVEL_DEFAULT: Default cluster level,
312  *   equal to @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES.
313  *
314  * Since: 0.9.42
315  */
316 typedef enum {
317   HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES	= 0,
318   HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS	= 1,
319   HB_BUFFER_CLUSTER_LEVEL_CHARACTERS		= 2,
320   HB_BUFFER_CLUSTER_LEVEL_DEFAULT = HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES
321 } hb_buffer_cluster_level_t;
322 
323 HB_EXTERN void
324 hb_buffer_set_cluster_level (hb_buffer_t               *buffer,
325 			     hb_buffer_cluster_level_t  cluster_level);
326 
327 HB_EXTERN hb_buffer_cluster_level_t
328 hb_buffer_get_cluster_level (hb_buffer_t *buffer);
329 
330 /**
331  * HB_BUFFER_REPLACEMENT_CODEPOINT_DEFAULT:
332  *
333  * The default code point for replacing invalid characters in a given encoding.
334  * Set to U+FFFD REPLACEMENT CHARACTER.
335  *
336  * Since: 0.9.31
337  */
338 #define HB_BUFFER_REPLACEMENT_CODEPOINT_DEFAULT 0xFFFDu
339 
340 HB_EXTERN void
341 hb_buffer_set_replacement_codepoint (hb_buffer_t    *buffer,
342 				     hb_codepoint_t  replacement);
343 
344 HB_EXTERN hb_codepoint_t
345 hb_buffer_get_replacement_codepoint (hb_buffer_t    *buffer);
346 
347 HB_EXTERN void
348 hb_buffer_set_invisible_glyph (hb_buffer_t    *buffer,
349 			       hb_codepoint_t  invisible);
350 
351 HB_EXTERN hb_codepoint_t
352 hb_buffer_get_invisible_glyph (hb_buffer_t    *buffer);
353 
354 
355 HB_EXTERN void
356 hb_buffer_reset (hb_buffer_t *buffer);
357 
358 HB_EXTERN void
359 hb_buffer_clear_contents (hb_buffer_t *buffer);
360 
361 HB_EXTERN hb_bool_t
362 hb_buffer_pre_allocate (hb_buffer_t  *buffer,
363 		        unsigned int  size);
364 
365 
366 HB_EXTERN hb_bool_t
367 hb_buffer_allocation_successful (hb_buffer_t  *buffer);
368 
369 HB_EXTERN void
370 hb_buffer_reverse (hb_buffer_t *buffer);
371 
372 HB_EXTERN void
373 hb_buffer_reverse_range (hb_buffer_t *buffer,
374 			 unsigned int start, unsigned int end);
375 
376 HB_EXTERN void
377 hb_buffer_reverse_clusters (hb_buffer_t *buffer);
378 
379 
380 /* Filling the buffer in */
381 
382 HB_EXTERN void
383 hb_buffer_add (hb_buffer_t    *buffer,
384 	       hb_codepoint_t  codepoint,
385 	       unsigned int    cluster);
386 
387 HB_EXTERN void
388 hb_buffer_add_utf8 (hb_buffer_t  *buffer,
389 		    const char   *text,
390 		    int           text_length,
391 		    unsigned int  item_offset,
392 		    int           item_length);
393 
394 HB_EXTERN void
395 hb_buffer_add_utf16 (hb_buffer_t    *buffer,
396 		     const uint16_t *text,
397 		     int             text_length,
398 		     unsigned int    item_offset,
399 		     int             item_length);
400 
401 HB_EXTERN void
402 hb_buffer_add_utf32 (hb_buffer_t    *buffer,
403 		     const uint32_t *text,
404 		     int             text_length,
405 		     unsigned int    item_offset,
406 		     int             item_length);
407 
408 HB_EXTERN void
409 hb_buffer_add_latin1 (hb_buffer_t   *buffer,
410 		      const uint8_t *text,
411 		      int            text_length,
412 		      unsigned int   item_offset,
413 		      int            item_length);
414 
415 HB_EXTERN void
416 hb_buffer_add_codepoints (hb_buffer_t          *buffer,
417 			  const hb_codepoint_t *text,
418 			  int                   text_length,
419 			  unsigned int          item_offset,
420 			  int                   item_length);
421 
422 HB_EXTERN void
423 hb_buffer_append (hb_buffer_t *buffer,
424 		  hb_buffer_t *source,
425 		  unsigned int start,
426 		  unsigned int end);
427 
428 HB_EXTERN hb_bool_t
429 hb_buffer_set_length (hb_buffer_t  *buffer,
430 		      unsigned int  length);
431 
432 HB_EXTERN unsigned int
433 hb_buffer_get_length (hb_buffer_t *buffer);
434 
435 /* Getting glyphs out of the buffer */
436 
437 HB_EXTERN hb_glyph_info_t *
438 hb_buffer_get_glyph_infos (hb_buffer_t  *buffer,
439                            unsigned int *length);
440 
441 HB_EXTERN hb_glyph_position_t *
442 hb_buffer_get_glyph_positions (hb_buffer_t  *buffer,
443                                unsigned int *length);
444 
445 
446 HB_EXTERN void
447 hb_buffer_normalize_glyphs (hb_buffer_t *buffer);
448 
449 
450 /*
451  * Serialize
452  */
453 
454 /**
455  * hb_buffer_serialize_flags_t:
456  * @HB_BUFFER_SERIALIZE_FLAG_DEFAULT: serialize glyph names, clusters and positions.
457  * @HB_BUFFER_SERIALIZE_FLAG_NO_CLUSTERS: do not serialize glyph cluster.
458  * @HB_BUFFER_SERIALIZE_FLAG_NO_POSITIONS: do not serialize glyph position information.
459  * @HB_BUFFER_SERIALIZE_FLAG_NO_GLYPH_NAMES: do no serialize glyph name.
460  * @HB_BUFFER_SERIALIZE_FLAG_GLYPH_EXTENTS: serialize glyph extents.
461  * @HB_BUFFER_SERIALIZE_FLAG_GLYPH_FLAGS: serialize glyph flags. Since: 1.5.0
462  * @HB_BUFFER_SERIALIZE_FLAG_NO_ADVANCES: do not serialize glyph advances,
463  *  glyph offsets will reflect absolute glyph positions. Since: 1.8.0
464  *
465  * Flags that control what glyph information are serialized in hb_buffer_serialize_glyphs().
466  *
467  * Since: 0.9.20
468  */
469 typedef enum { /*< flags >*/
470   HB_BUFFER_SERIALIZE_FLAG_DEFAULT		= 0x00000000u,
471   HB_BUFFER_SERIALIZE_FLAG_NO_CLUSTERS		= 0x00000001u,
472   HB_BUFFER_SERIALIZE_FLAG_NO_POSITIONS		= 0x00000002u,
473   HB_BUFFER_SERIALIZE_FLAG_NO_GLYPH_NAMES	= 0x00000004u,
474   HB_BUFFER_SERIALIZE_FLAG_GLYPH_EXTENTS	= 0x00000008u,
475   HB_BUFFER_SERIALIZE_FLAG_GLYPH_FLAGS		= 0x00000010u,
476   HB_BUFFER_SERIALIZE_FLAG_NO_ADVANCES		= 0x00000020u
477 } hb_buffer_serialize_flags_t;
478 
479 /**
480  * hb_buffer_serialize_format_t:
481  * @HB_BUFFER_SERIALIZE_FORMAT_TEXT: a human-readable, plain text format.
482  * @HB_BUFFER_SERIALIZE_FORMAT_JSON: a machine-readable JSON format.
483  * @HB_BUFFER_SERIALIZE_FORMAT_INVALID: invalid format.
484  *
485  * The buffer serialization and de-serialization format used in
486  * hb_buffer_serialize_glyphs() and hb_buffer_deserialize_glyphs().
487  *
488  * Since: 0.9.2
489  */
490 typedef enum {
491   HB_BUFFER_SERIALIZE_FORMAT_TEXT	= HB_TAG('T','E','X','T'),
492   HB_BUFFER_SERIALIZE_FORMAT_JSON	= HB_TAG('J','S','O','N'),
493   HB_BUFFER_SERIALIZE_FORMAT_INVALID	= HB_TAG_NONE
494 } hb_buffer_serialize_format_t;
495 
496 HB_EXTERN hb_buffer_serialize_format_t
497 hb_buffer_serialize_format_from_string (const char *str, int len);
498 
499 HB_EXTERN const char *
500 hb_buffer_serialize_format_to_string (hb_buffer_serialize_format_t format);
501 
502 HB_EXTERN const char **
503 hb_buffer_serialize_list_formats (void);
504 
505 HB_EXTERN unsigned int
506 hb_buffer_serialize_glyphs (hb_buffer_t *buffer,
507 			    unsigned int start,
508 			    unsigned int end,
509 			    char *buf,
510 			    unsigned int buf_size,
511 			    unsigned int *buf_consumed,
512 			    hb_font_t *font,
513 			    hb_buffer_serialize_format_t format,
514 			    hb_buffer_serialize_flags_t flags);
515 
516 HB_EXTERN hb_bool_t
517 hb_buffer_deserialize_glyphs (hb_buffer_t *buffer,
518 			      const char *buf,
519 			      int buf_len,
520 			      const char **end_ptr,
521 			      hb_font_t *font,
522 			      hb_buffer_serialize_format_t format);
523 
524 
525 /*
526  * Compare buffers
527  */
528 
529 typedef enum { /*< flags >*/
530   HB_BUFFER_DIFF_FLAG_EQUAL			= 0x0000,
531 
532   /* Buffers with different content_type cannot be meaningfully compared
533    * in any further detail. */
534   HB_BUFFER_DIFF_FLAG_CONTENT_TYPE_MISMATCH	= 0x0001,
535 
536   /* For buffers with differing length, the per-glyph comparison is not
537    * attempted, though we do still scan reference for dottedcircle / .notdef
538    * glyphs. */
539   HB_BUFFER_DIFF_FLAG_LENGTH_MISMATCH		= 0x0002,
540 
541   /* We want to know if dottedcircle / .notdef glyphs are present in the
542    * reference, as we may not care so much about other differences in this
543    * case. */
544   HB_BUFFER_DIFF_FLAG_NOTDEF_PRESENT		= 0x0004,
545   HB_BUFFER_DIFF_FLAG_DOTTED_CIRCLE_PRESENT	= 0x0008,
546 
547   /* If the buffers have the same length, we compare them glyph-by-glyph
548    * and report which aspect(s) of the glyph info/position are different. */
549   HB_BUFFER_DIFF_FLAG_CODEPOINT_MISMATCH	= 0x0010,
550   HB_BUFFER_DIFF_FLAG_CLUSTER_MISMATCH		= 0x0020,
551   HB_BUFFER_DIFF_FLAG_GLYPH_FLAGS_MISMATCH	= 0x0040,
552   HB_BUFFER_DIFF_FLAG_POSITION_MISMATCH		= 0x0080
553 
554 } hb_buffer_diff_flags_t;
555 
556 /* Compare the contents of two buffers, report types of differences. */
557 HB_EXTERN hb_buffer_diff_flags_t
558 hb_buffer_diff (hb_buffer_t *buffer,
559 		hb_buffer_t *reference,
560 		hb_codepoint_t dottedcircle_glyph,
561 		unsigned int position_fuzz);
562 
563 
564 /*
565  * Debugging.
566  */
567 
568 typedef hb_bool_t	(*hb_buffer_message_func_t)	(hb_buffer_t *buffer,
569 							 hb_font_t   *font,
570 							 const char  *message,
571 							 void        *user_data);
572 
573 HB_EXTERN void
574 hb_buffer_set_message_func (hb_buffer_t *buffer,
575 			    hb_buffer_message_func_t func,
576 			    void *user_data, hb_destroy_func_t destroy);
577 
578 
579 HB_END_DECLS
580 
581 #endif /* HB_BUFFER_H */
582