hb-ot-shape.cc revision 6bd9b479b8b2befbb0847282e93beade197c8038 
1/*
2 * Copyright © 2009,2010  Red Hat, Inc.
3 * Copyright © 2010,2011  Google, Inc.
4 *
5 *  This is part of HarfBuzz, a text shaping library.
6 *
7 * Permission is hereby granted, without written agreement and without
8 * license or royalty fees, to use, copy, modify, and distribute this
9 * software and its documentation for any purpose, provided that the
10 * above copyright notice and the following two paragraphs appear in
11 * all copies of this software.
12 *
13 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
14 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
15 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
16 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
17 * DAMAGE.
18 *
19 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
20 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
21 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
22 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
23 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
24 *
25 * Red Hat Author(s): Behdad Esfahbod
26 * Google Author(s): Behdad Esfahbod
27 */
28
29#include "hb-ot-shape-private.hh"
30#include "hb-ot-shape-complex-private.hh"
31
32#include "hb-font-private.hh"
33
34
35
36hb_tag_t common_features[] = {
37  HB_TAG('c','c','m','p'),
38  HB_TAG('l','o','c','l'),
39  HB_TAG('m','a','r','k'),
40  HB_TAG('m','k','m','k'),
41  HB_TAG('r','l','i','g'),
42};
43
44hb_tag_t horizontal_features[] = {
45  HB_TAG('c','a','l','t'),
46  HB_TAG('c','l','i','g'),
47  HB_TAG('c','u','r','s'),
48  HB_TAG('k','e','r','n'),
49  HB_TAG('l','i','g','a'),
50};
51
52/* Note:
53 * Technically speaking, vrt2 and vert are mutually exclusive.
54 * According to the spec, valt and vpal are also mutually exclusive.
55 * But we apply them all for now.
56 */
57hb_tag_t vertical_features[] = {
58  HB_TAG('v','a','l','t'),
59  HB_TAG('v','e','r','t'),
60  HB_TAG('v','k','r','n'),
61  HB_TAG('v','p','a','l'),
62  HB_TAG('v','r','t','2'),
63};
64
65static void
66hb_ot_shape_collect_features (hb_ot_shape_planner_t          *planner,
67			      const hb_segment_properties_t  *props,
68			      const hb_feature_t             *user_features,
69			      unsigned int                    num_user_features)
70{
71  switch (props->direction) {
72    case HB_DIRECTION_LTR:
73      planner->map.add_bool_feature (HB_TAG ('l','t','r','a'));
74      planner->map.add_bool_feature (HB_TAG ('l','t','r','m'));
75      break;
76    case HB_DIRECTION_RTL:
77      planner->map.add_bool_feature (HB_TAG ('r','t','l','a'));
78      planner->map.add_bool_feature (HB_TAG ('r','t','l','m'), false);
79      break;
80    case HB_DIRECTION_TTB:
81    case HB_DIRECTION_BTT:
82    case HB_DIRECTION_INVALID:
83    default:
84      break;
85  }
86
87#define ADD_FEATURES(array) \
88  HB_STMT_START { \
89    for (unsigned int i = 0; i < ARRAY_LENGTH (array); i++) \
90      planner->map.add_bool_feature (array[i]); \
91  } HB_STMT_END
92
93  hb_ot_shape_complex_collect_features (planner->shaper, &planner->map, props);
94
95  ADD_FEATURES (common_features);
96
97  if (HB_DIRECTION_IS_HORIZONTAL (props->direction))
98    ADD_FEATURES (horizontal_features);
99  else
100    ADD_FEATURES (vertical_features);
101
102#undef ADD_FEATURES
103
104  for (unsigned int i = 0; i < num_user_features; i++) {
105    const hb_feature_t *feature = &user_features[i];
106    planner->map.add_feature (feature->tag, feature->value, (feature->start == 0 && feature->end == (unsigned int) -1));
107  }
108}
109
110
111static void
112hb_ot_shape_setup_masks (hb_ot_shape_context_t *c)
113{
114  hb_mask_t global_mask = c->plan->map.get_global_mask ();
115  c->buffer->reset_masks (global_mask);
116
117  hb_ot_shape_complex_setup_masks (c->plan->shaper, &c->plan->map, c->buffer, c->font);
118
119  for (unsigned int i = 0; i < c->num_user_features; i++)
120  {
121    const hb_feature_t *feature = &c->user_features[i];
122    if (!(feature->start == 0 && feature->end == (unsigned int)-1)) {
123      unsigned int shift;
124      hb_mask_t mask = c->plan->map.get_mask (feature->tag, &shift);
125      c->buffer->set_masks (feature->value << shift, mask, feature->start, feature->end);
126    }
127  }
128}
129
130
131/* Main shaper */
132
133/* Prepare */
134
135void
136_hb_set_unicode_props (hb_buffer_t *buffer)
137{
138  unsigned int count = buffer->len;
139  for (unsigned int i = 0; i < count; i++)
140    hb_glyph_info_set_unicode_props (&buffer->info[i], buffer->unicode);
141}
142
143static void
144hb_form_clusters (hb_buffer_t *buffer)
145{
146  unsigned int count = buffer->len;
147  for (unsigned int i = 1; i < count; i++)
148    if (FLAG (buffer->info[i].general_category()) &
149	(FLAG (HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK) |
150	 FLAG (HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) |
151	 FLAG (HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)))
152      buffer->info[i].cluster = buffer->info[i - 1].cluster;
153}
154
155static void
156hb_ensure_native_direction (hb_buffer_t *buffer)
157{
158  hb_direction_t direction = buffer->props.direction;
159
160  /* TODO vertical:
161   * The only BTT vertical script is Ogham, but it's not clear to me whether OpenType
162   * Ogham fonts are supposed to be implemented BTT or not.  Need to research that
163   * first. */
164  if ((HB_DIRECTION_IS_HORIZONTAL (direction) && direction != hb_script_get_horizontal_direction (buffer->props.script)) ||
165      (HB_DIRECTION_IS_VERTICAL   (direction) && direction != HB_DIRECTION_TTB))
166  {
167    hb_buffer_reverse_clusters (buffer);
168    buffer->props.direction = HB_DIRECTION_REVERSE (buffer->props.direction);
169  }
170}
171
172
173/* Substitute */
174
175static void
176hb_mirror_chars (hb_ot_shape_context_t *c)
177{
178  hb_unicode_funcs_t *unicode = c->buffer->unicode;
179
180  if (HB_DIRECTION_IS_FORWARD (c->target_direction))
181    return;
182
183  hb_mask_t rtlm_mask = c->plan->map.get_1_mask (HB_TAG ('r','t','l','m'));
184
185  unsigned int count = c->buffer->len;
186  for (unsigned int i = 0; i < count; i++) {
187    hb_codepoint_t codepoint = hb_unicode_mirroring (unicode, c->buffer->info[i].codepoint);
188    if (likely (codepoint == c->buffer->info[i].codepoint))
189      c->buffer->info[i].mask |= rtlm_mask; /* XXX this should be moved to before setting user-feature masks */
190    else
191      c->buffer->info[i].codepoint = codepoint;
192  }
193}
194
195static void
196hb_map_glyphs (hb_font_t    *font,
197	       hb_buffer_t  *buffer)
198{
199  hb_codepoint_t glyph;
200
201  if (unlikely (!buffer->len))
202    return;
203
204  buffer->clear_output ();
205
206  unsigned int count = buffer->len - 1;
207  for (buffer->idx = 0; buffer->idx < count;) {
208    if (unlikely (_hb_unicode_is_variation_selector (buffer->info[buffer->idx + 1].codepoint))) {
209      hb_font_get_glyph (font, buffer->info[buffer->idx].codepoint, buffer->info[buffer->idx + 1].codepoint, &glyph);
210      buffer->replace_glyph (glyph);
211      buffer->skip_glyph ();
212    } else {
213      hb_font_get_glyph (font, buffer->info[buffer->idx].codepoint, 0, &glyph);
214      buffer->replace_glyph (glyph);
215    }
216  }
217  if (likely (buffer->idx < buffer->len)) {
218    hb_font_get_glyph (font, buffer->info[buffer->idx].codepoint, 0, &glyph);
219    buffer->replace_glyph (glyph);
220  }
221  buffer->swap_buffers ();
222}
223
224static void
225hb_substitute_default (hb_ot_shape_context_t *c)
226{
227  hb_ot_layout_substitute_start (c->buffer);
228
229  hb_mirror_chars (c);
230
231  hb_map_glyphs (c->font, c->buffer);
232}
233
234static void
235hb_ot_substitute_complex (hb_ot_shape_context_t *c)
236{
237  if (hb_ot_layout_has_substitution (c->face)) {
238    c->plan->map.substitute (c->face, c->buffer);
239  }
240
241  hb_ot_layout_substitute_finish (c->buffer);
242
243  return;
244}
245
246
247/* Position */
248
249static void
250hb_position_default (hb_ot_shape_context_t *c)
251{
252  hb_ot_layout_position_start (c->buffer);
253
254  unsigned int count = c->buffer->len;
255  for (unsigned int i = 0; i < count; i++) {
256    hb_font_get_glyph_advance_for_direction (c->font, c->buffer->info[i].codepoint,
257					     c->buffer->props.direction,
258					     &c->buffer->pos[i].x_advance,
259					     &c->buffer->pos[i].y_advance);
260    hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
261						 c->buffer->props.direction,
262						 &c->buffer->pos[i].x_offset,
263						 &c->buffer->pos[i].y_offset);
264  }
265}
266
267static void
268hb_ot_position_complex (hb_ot_shape_context_t *c)
269{
270
271  if (hb_ot_layout_has_positioning (c->face))
272  {
273    /* Change glyph origin to what GPOS expects, apply GPOS, change it back. */
274
275    unsigned int count = c->buffer->len;
276    for (unsigned int i = 0; i < count; i++) {
277      hb_font_add_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
278					      HB_DIRECTION_LTR,
279					      &c->buffer->pos[i].x_offset,
280					      &c->buffer->pos[i].y_offset);
281    }
282
283    c->plan->map.position (c->font, c->buffer);
284
285    for (unsigned int i = 0; i < count; i++) {
286      hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
287						   HB_DIRECTION_LTR,
288						   &c->buffer->pos[i].x_offset,
289						   &c->buffer->pos[i].y_offset);
290    }
291
292    c->applied_position_complex = TRUE;
293  }
294
295  hb_ot_layout_position_finish (c->buffer);
296
297  return;
298}
299
300static void
301hb_position_complex_fallback (hb_ot_shape_context_t *c HB_UNUSED)
302{
303  /* TODO Mark pos */
304}
305
306static void
307hb_truetype_kern (hb_ot_shape_context_t *c)
308{
309  /* TODO Check for kern=0 */
310  unsigned int count = c->buffer->len;
311  for (unsigned int i = 1; i < count; i++) {
312    hb_position_t x_kern, y_kern, kern1, kern2;
313    hb_font_get_glyph_kerning_for_direction (c->font,
314					     c->buffer->info[i - 1].codepoint, c->buffer->info[i].codepoint,
315					     c->buffer->props.direction,
316					     &x_kern, &y_kern);
317
318    kern1 = x_kern >> 1;
319    kern2 = x_kern - kern1;
320    c->buffer->pos[i - 1].x_advance += kern1;
321    c->buffer->pos[i].x_advance += kern2;
322    c->buffer->pos[i].x_offset += kern2;
323
324    kern1 = y_kern >> 1;
325    kern2 = y_kern - kern1;
326    c->buffer->pos[i - 1].y_advance += kern1;
327    c->buffer->pos[i].y_advance += kern2;
328    c->buffer->pos[i].y_offset += kern2;
329  }
330}
331
332static void
333hb_position_complex_fallback_visual (hb_ot_shape_context_t *c)
334{
335  hb_truetype_kern (c);
336}
337
338
339/* Do it! */
340
341static void
342hb_ot_shape_execute_internal (hb_ot_shape_context_t *c)
343{
344  c->buffer->deallocate_var_all ();
345
346  /* Save the original direction, we use it later. */
347  c->target_direction = c->buffer->props.direction;
348
349  HB_BUFFER_ALLOCATE_VAR (c->buffer, general_category);
350  HB_BUFFER_ALLOCATE_VAR (c->buffer, combining_class);
351
352  _hb_set_unicode_props (c->buffer); /* BUFFER: Set general_category and combining_class */
353
354  hb_form_clusters (c->buffer);
355
356  hb_ensure_native_direction (c->buffer);
357
358  _hb_ot_shape_normalize (c->font, c->buffer, hb_ot_shape_complex_normalization_preference (c->plan->shaper));
359
360  hb_ot_shape_setup_masks (c);
361
362  /* SUBSTITUTE */
363  {
364    hb_substitute_default (c);
365
366    hb_ot_substitute_complex (c);
367  }
368
369  /* POSITION */
370  {
371    hb_position_default (c);
372
373    hb_ot_position_complex (c);
374
375    hb_bool_t position_fallback = !c->applied_position_complex;
376    if (position_fallback)
377      hb_position_complex_fallback (c);
378
379    if (HB_DIRECTION_IS_BACKWARD (c->buffer->props.direction))
380      hb_buffer_reverse (c->buffer);
381
382    if (position_fallback)
383      hb_position_complex_fallback_visual (c);
384  }
385
386  HB_BUFFER_DEALLOCATE_VAR (c->buffer, combining_class);
387  HB_BUFFER_DEALLOCATE_VAR (c->buffer, general_category);
388
389  c->buffer->props.direction = c->target_direction;
390
391  c->buffer->deallocate_var_all ();
392}
393
394static void
395hb_ot_shape_plan_internal (hb_ot_shape_plan_t       *plan,
396			   hb_face_t                *face,
397			   const hb_segment_properties_t  *props,
398			   const hb_feature_t       *user_features,
399			   unsigned int              num_user_features)
400{
401  hb_ot_shape_planner_t planner;
402
403  planner.shaper = hb_ot_shape_complex_categorize (props);
404
405  hb_ot_shape_collect_features (&planner, props, user_features, num_user_features);
406
407  planner.compile (face, props, *plan);
408}
409
410static void
411hb_ot_shape_execute (hb_ot_shape_plan_t *plan,
412		     hb_font_t          *font,
413		     hb_buffer_t        *buffer,
414		     const hb_feature_t *user_features,
415		     unsigned int        num_user_features)
416{
417  hb_ot_shape_context_t c = {plan, font, font->face, buffer, user_features, num_user_features};
418  hb_ot_shape_execute_internal (&c);
419}
420
421hb_bool_t
422_hb_ot_shape (hb_font_t          *font,
423	      hb_buffer_t        *buffer,
424	      const hb_feature_t *features,
425	      unsigned int        num_features)
426{
427  hb_ot_shape_plan_t plan;
428
429  buffer->guess_properties ();
430
431  hb_ot_shape_plan_internal (&plan, font->face, &buffer->props, features, num_features);
432  hb_ot_shape_execute (&plan, font, buffer, features, num_features);
433
434  return TRUE;
435}
436