src/hb-ot-shape.cc

   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 HB_BEGIN_DECLS
  35
  36
  37 hb_tag_t common_features[] = {
  38   HB_TAG('c','c','m','p'),
  39   HB_TAG('l','o','c','l'),
  40   HB_TAG('m','a','r','k'),
  41   HB_TAG('m','k','m','k'),
  42   HB_TAG('r','l','i','g'),
  43 };
  44
  45 hb_tag_t horizontal_features[] = {
  46   HB_TAG('c','a','l','t'),
  47   HB_TAG('c','l','i','g'),
  48   HB_TAG('c','u','r','s'),
  49   HB_TAG('k','e','r','n'),
  50   HB_TAG('l','i','g','a'),
  51 };
  52
  53 /* Note:
  54  * Technically speaking, vrt2 and vert are mutually exclusive.
  55  * According to the spec, valt and vpal are also mutually exclusive.
  56  * But we apply them all for now.
  57  */
  58 hb_tag_t vertical_features[] = {
  59   HB_TAG('v','a','l','t'),
  60   HB_TAG('v','e','r','t'),
  61   HB_TAG('v','k','r','n'),
  62   HB_TAG('v','p','a','l'),
  63   HB_TAG('v','r','t','2'),
  64 };
  65
  66 static void
  67 hb_ot_shape_collect_features (hb_ot_shape_planner_t          *planner,
  68                               const hb_segment_properties_t  *props,
  69                               const hb_feature_t             *user_features,
  70                               unsigned int                    num_user_features)
  71 {
  72   switch (props->direction) {
  73     case HB_DIRECTION_LTR:
  74       planner->map.add_bool_feature (HB_TAG ('l','t','r','a'));
  75       planner->map.add_bool_feature (HB_TAG ('l','t','r','m'));
  76       break;
  77     case HB_DIRECTION_RTL:
  78       planner->map.add_bool_feature (HB_TAG ('r','t','l','a'));
  79       planner->map.add_bool_feature (HB_TAG ('r','t','l','m'), false);
  80       break;
  81     case HB_DIRECTION_TTB:
  82     case HB_DIRECTION_BTT:
  83     case HB_DIRECTION_INVALID:
  84     default:
  85       break;
  86   }
  87
  88 #define ADD_FEATURES(array) \
  89   HB_STMT_START { \
  90     for (unsigned int i = 0; i < ARRAY_LENGTH (array); i++) \
  91       planner->map.add_bool_feature (array[i]); \
  92   } HB_STMT_END
  93
  94   hb_ot_shape_complex_collect_features (planner->shaper, &planner->map, props);
  95
  96   ADD_FEATURES (common_features);
  97
  98   if (HB_DIRECTION_IS_HORIZONTAL (props->direction))
  99     ADD_FEATURES (horizontal_features);
 100   else
 101     ADD_FEATURES (vertical_features);
 102
 103 #undef ADD_FEATURES
 104
 105   for (unsigned int i = 0; i < num_user_features; i++) {
 106     const hb_feature_t *feature = &user_features[i];
 107     planner->map.add_feature (feature->tag, feature->value, (feature->start == 0 && feature->end == (unsigned int) -1));
 108   }
 109 }
 110
 111
 112 static void
 113 hb_ot_shape_setup_masks (hb_ot_shape_context_t *c)
 114 {
 115   hb_mask_t global_mask = c->plan->map.get_global_mask ();
 116   c->buffer->reset_masks (global_mask);
 117
 118   hb_ot_shape_complex_setup_masks (c->plan->shaper, &c->plan->map, c->buffer);
 119
 120   for (unsigned int i = 0; i < c->num_user_features; i++)
 121   {
 122     const hb_feature_t *feature = &c->user_features[i];
 123     if (!(feature->start == 0 && feature->end == (unsigned int)-1)) {
 124       unsigned int shift;
 125       hb_mask_t mask = c->plan->map.get_mask (feature->tag, &shift);
 126       c->buffer->set_masks (feature->value << shift, mask, feature->start, feature->end);
 127     }
 128   }
 129 }
 130
 131
 132 /* Main shaper */
 133
 134 /* Prepare */
 135
 136 void
 137 _hb_set_unicode_props (hb_buffer_t *buffer)
 138 {
 139   unsigned int count = buffer->len;
 140   for (unsigned int i = 1; i < count; i++)
 141     hb_glyph_info_set_unicode_props (&buffer->info[i], buffer->unicode);
 142 }
 143
 144 static void
 145 hb_form_clusters (hb_buffer_t *buffer)
 146 {
 147   unsigned int count = buffer->len;
 148   for (unsigned int i = 1; i < count; i++)
 149     if (FLAG (buffer->info[i].general_category()) &
 150         (FLAG (HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK) |
 151          FLAG (HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) |
 152          FLAG (HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)))
 153       buffer->info[i].cluster = buffer->info[i - 1].cluster;
 154 }
 155
 156 static void
 157 hb_ensure_native_direction (hb_buffer_t *buffer)
 158 {
 159   hb_direction_t direction = buffer->props.direction;
 160
 161   /* TODO vertical:
 162    * The only BTT vertical script is Ogham, but it's not clear to me whether OpenType
 163    * Ogham fonts are supposed to be implemented BTT or not.  Need to research that
 164    * first. */
 165   if ((HB_DIRECTION_IS_HORIZONTAL (direction) && direction != hb_script_get_horizontal_direction (buffer->props.script)) ||
 166       (HB_DIRECTION_IS_VERTICAL   (direction) && direction != HB_DIRECTION_TTB))
 167   {
 168     hb_buffer_reverse_clusters (buffer);
 169     buffer->props.direction = HB_DIRECTION_REVERSE (buffer->props.direction);
 170   }
 171 }
 172
 173
 174 /* Substitute */
 175
 176 static void
 177 hb_mirror_chars (hb_ot_shape_context_t *c)
 178 {
 179   hb_unicode_funcs_t *unicode = c->buffer->unicode;
 180
 181   if (HB_DIRECTION_IS_FORWARD (c->target_direction))
 182     return;
 183
 184   hb_mask_t rtlm_mask = c->plan->map.get_1_mask (HB_TAG ('r','t','l','m'));
 185
 186   unsigned int count = c->buffer->len;
 187   for (unsigned int i = 0; i < count; i++) {
 188     hb_codepoint_t codepoint = hb_unicode_mirroring (unicode, c->buffer->info[i].codepoint);
 189     if (likely (codepoint == c->buffer->info[i].codepoint))
 190       c->buffer->info[i].mask |= rtlm_mask; /* XXX this should be moved to before setting user-feature masks */
 191     else
 192       c->buffer->info[i].codepoint = codepoint;
 193   }
 194 }
 195
 196 static void
 197 hb_map_glyphs (hb_font_t    *font,
 198                hb_buffer_t  *buffer)
 199 {
 200   hb_codepoint_t glyph;
 201
 202   if (unlikely (!buffer->len))
 203     return;
 204
 205   buffer->clear_output ();
 206
 207   unsigned int count = buffer->len - 1;
 208   for (buffer->idx = 0; buffer->idx < count;) {
 209     if (unlikely (is_variation_selector (buffer->info[buffer->idx + 1].codepoint))) {
 210       hb_font_get_glyph (font, buffer->info[buffer->idx].codepoint, buffer->info[buffer->idx + 1].codepoint, &glyph);
 211       buffer->replace_glyph (glyph);
 212       buffer->skip_glyph ();
 213     } else {
 214       hb_font_get_glyph (font, buffer->info[buffer->idx].codepoint, 0, &glyph);
 215       buffer->replace_glyph (glyph);
 216     }
 217   }
 218   if (likely (buffer->idx < buffer->len)) {
 219     hb_font_get_glyph (font, buffer->info[buffer->idx].codepoint, 0, &glyph);
 220     buffer->replace_glyph (glyph);
 221   }
 222   buffer->swap_buffers ();
 223 }
 224
 225 static void
 226 hb_substitute_default (hb_ot_shape_context_t *c)
 227 {
 228   hb_ot_layout_substitute_start (c->buffer);
 229
 230   hb_mirror_chars (c);
 231
 232   hb_map_glyphs (c->font, c->buffer);
 233 }
 234
 235 static void
 236 hb_ot_substitute_complex (hb_ot_shape_context_t *c)
 237 {
 238   if (hb_ot_layout_has_substitution (c->face))
 239     c->plan->map.substitute (c->face, c->buffer);
 240
 241   hb_ot_layout_substitute_finish (c->buffer);
 242
 243   c->applied_substitute_complex = TRUE;
 244   return;
 245 }
 246
 247 static void
 248 hb_substitute_complex_fallback (hb_ot_shape_context_t *c HB_UNUSED)
 249 {
 250   /* TODO Arabic */
 251 }
 252
 253
 254 /* Position */
 255
 256 static void
 257 hb_position_default (hb_ot_shape_context_t *c)
 258 {
 259   hb_ot_layout_position_start (c->buffer);
 260
 261   unsigned int count = c->buffer->len;
 262   for (unsigned int i = 0; i < count; i++) {
 263     hb_font_get_glyph_advance_for_direction (c->font, c->buffer->info[i].codepoint,
 264                                              c->buffer->props.direction,
 265                                              &c->buffer->pos[i].x_advance,
 266                                              &c->buffer->pos[i].y_advance);
 267     hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
 268                                                  c->buffer->props.direction,
 269                                                  &c->buffer->pos[i].x_offset,
 270                                                  &c->buffer->pos[i].y_offset);
 271   }
 272 }
 273
 274 static void
 275 hb_ot_position_complex (hb_ot_shape_context_t *c)
 276 {
 277
 278   if (hb_ot_layout_has_positioning (c->face))
 279   {
 280     /* Change glyph origin to what GPOS expects, apply GPOS, change it back. */
 281
 282     unsigned int count = c->buffer->len;
 283     for (unsigned int i = 0; i < count; i++) {
 284       hb_font_add_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
 285                                               HB_DIRECTION_LTR,
 286                                               &c->buffer->pos[i].x_offset,
 287                                               &c->buffer->pos[i].y_offset);
 288     }
 289
 290     c->plan->map.position (c->font, c->buffer);
 291
 292     for (unsigned int i = 0; i < count; i++) {
 293       hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
 294                                                    HB_DIRECTION_LTR,
 295                                                    &c->buffer->pos[i].x_offset,
 296                                                    &c->buffer->pos[i].y_offset);
 297     }
 298   }
 299
 300   hb_ot_layout_position_finish (c->buffer);
 301
 302   c->applied_position_complex = TRUE;
 303   return;
 304 }
 305
 306 static void
 307 hb_position_complex_fallback (hb_ot_shape_context_t *c HB_UNUSED)
 308 {
 309   /* TODO Mark pos */
 310 }
 311
 312 static void
 313 hb_truetype_kern (hb_ot_shape_context_t *c)
 314 {
 315   /* TODO Check for kern=0 */
 316   unsigned int count = c->buffer->len;
 317   for (unsigned int i = 1; i < count; i++) {
 318     hb_position_t x_kern, y_kern, kern1, kern2;
 319     hb_font_get_glyph_kerning_for_direction (c->font,
 320                                              c->buffer->info[i - 1].codepoint, c->buffer->info[i].codepoint,
 321                                              c->buffer->props.direction,
 322                                              &x_kern, &y_kern);
 323
 324     kern1 = x_kern >> 1;
 325     kern2 = x_kern - kern1;
 326     c->buffer->pos[i - 1].x_advance += kern1;
 327     c->buffer->pos[i].x_advance += kern2;
 328     c->buffer->pos[i].x_offset += kern2;
 329
 330     kern1 = y_kern >> 1;
 331     kern2 = y_kern - kern1;
 332     c->buffer->pos[i - 1].y_advance += kern1;
 333     c->buffer->pos[i].y_advance += kern2;
 334     c->buffer->pos[i].y_offset += kern2;
 335   }
 336 }
 337
 338 static void
 339 hb_position_complex_fallback_visual (hb_ot_shape_context_t *c)
 340 {
 341   hb_truetype_kern (c);
 342 }
 343
 344
 345 /* Do it! */
 346
 347 static void
 348 hb_ot_shape_execute_internal (hb_ot_shape_context_t *c)
 349 {
 350   c->buffer->deallocate_var_all ();
 351
 352   /* Save the original direction, we use it later. */
 353   c->target_direction = c->buffer->props.direction;
 354
 355   HB_BUFFER_ALLOCATE_VAR (c->buffer, general_category);
 356   HB_BUFFER_ALLOCATE_VAR (c->buffer, combining_class);
 357
 358   _hb_set_unicode_props (c->buffer); /* BUFFER: Set general_category and combining_class */
 359
 360   hb_form_clusters (c->buffer);
 361
 362   hb_ensure_native_direction (c->buffer);
 363
 364   _hb_ot_shape_normalize (c);
 365
 366   hb_ot_shape_setup_masks (c);
 367
 368   /* SUBSTITUTE */
 369   {
 370     hb_substitute_default (c);
 371
 372     hb_ot_substitute_complex (c);
 373
 374     if (!c->applied_substitute_complex)
 375       hb_substitute_complex_fallback (c);
 376   }
 377
 378   /* POSITION */
 379   {
 380     hb_position_default (c);
 381
 382     hb_ot_position_complex (c);
 383
 384     hb_bool_t position_fallback = !c->applied_position_complex;
 385     if (position_fallback)
 386       hb_position_complex_fallback (c);
 387
 388     if (HB_DIRECTION_IS_BACKWARD (c->buffer->props.direction))
 389       hb_buffer_reverse (c->buffer);
 390
 391     if (position_fallback)
 392       hb_position_complex_fallback_visual (c);
 393   }
 394
 395   HB_BUFFER_DEALLOCATE_VAR (c->buffer, combining_class);
 396   HB_BUFFER_DEALLOCATE_VAR (c->buffer, general_category);
 397
 398   c->buffer->props.direction = c->target_direction;
 399
 400   c->buffer->deallocate_var_all ();
 401 }
 402
 403 static void
 404 hb_ot_shape_plan_internal (hb_ot_shape_plan_t       *plan,
 405                            hb_face_t                *face,
 406                            const hb_segment_properties_t  *props,
 407                            const hb_feature_t       *user_features,
 408                            unsigned int              num_user_features)
 409 {
 410   hb_ot_shape_planner_t planner;
 411
 412   planner.shaper = hb_ot_shape_complex_categorize (props);
 413
 414   hb_ot_shape_collect_features (&planner, props, user_features, num_user_features);
 415
 416   planner.compile (face, props, *plan);
 417 }
 418
 419 static void
 420 hb_ot_shape_execute (hb_ot_shape_plan_t *plan,
 421                      hb_font_t          *font,
 422                      hb_buffer_t        *buffer,
 423                      const hb_feature_t *user_features,
 424                      unsigned int        num_user_features)
 425 {
 426   hb_ot_shape_context_t c = {plan, font, font->face, buffer, user_features, num_user_features};
 427   hb_ot_shape_execute_internal (&c);
 428 }
 429
 430 void
 431 hb_ot_shape (hb_font_t          *font,
 432              hb_buffer_t        *buffer,
 433              const hb_feature_t *features,
 434              unsigned int        num_features)
 435 {
 436   hb_ot_shape_plan_t plan;
 437
 438   hb_ot_shape_plan_internal (&plan, font->face, &buffer->props, features, num_features);
 439   hb_ot_shape_execute (&plan, font, buffer, features, num_features);
 440 }
 441
 442
 443 HB_END_DECLS