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); /* BUFFER: Clobbers var2 */
 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 static void
 133 hb_ot_substitute_complex (hb_ot_shape_context_t *c)
 134 {
 135   if (!hb_ot_layout_has_substitution (c->face))
 136     return;
 137
 138   c->plan->map.substitute (c->face, c->buffer);
 139
 140   c->applied_substitute_complex = TRUE;
 141   return;
 142 }
 143
 144 static void
 145 hb_ot_position_complex (hb_ot_shape_context_t *c)
 146 {
 147
 148   if (!hb_ot_layout_has_positioning (c->face))
 149     return;
 150
 151   unsigned int count = c->buffer->len;
 152   for (unsigned int i = 0; i < count; i++) {
 153     hb_font_add_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
 154                                             HB_DIRECTION_LTR,
 155                                             &c->buffer->pos[i].x_offset,
 156                                             &c->buffer->pos[i].y_offset);
 157   }
 158
 159   c->plan->map.position (c->font, c->buffer);
 160
 161   for (unsigned int i = 0; i < count; i++) {
 162     hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
 163                                                  HB_DIRECTION_LTR,
 164                                                  &c->buffer->pos[i].x_offset,
 165                                                  &c->buffer->pos[i].y_offset);
 166   }
 167
 168   hb_ot_layout_position_finish (c->buffer);
 169
 170   c->applied_position_complex = TRUE;
 171   return;
 172 }
 173
 174
 175 /* Main shaper */
 176
 177 /* Prepare */
 178
 179 static void
 180 hb_set_unicode_props (hb_buffer_t *buffer)
 181 {
 182   unsigned int count = buffer->len;
 183   for (unsigned int i = 1; i < count; i++)
 184     hb_glyph_info_set_unicode_props (&buffer->info[i], buffer->unicode);
 185 }
 186
 187 static void
 188 hb_form_clusters (hb_buffer_t *buffer)
 189 {
 190   unsigned int count = buffer->len;
 191   for (unsigned int i = 1; i < count; i++)
 192     if (FLAG (buffer->info[i].general_category()) &
 193         (FLAG (HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK) |
 194          FLAG (HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) |
 195          FLAG (HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)))
 196       buffer->info[i].cluster = buffer->info[i - 1].cluster;
 197 }
 198
 199 static void
 200 hb_ensure_native_direction (hb_buffer_t *buffer)
 201 {
 202   hb_direction_t direction = buffer->props.direction;
 203
 204   /* TODO vertical:
 205    * The only BTT vertical script is Ogham, but it's not clear to me whether OpenType
 206    * Ogham fonts are supposed to be implemented BTT or not.  Need to research that
 207    * first. */
 208   if ((HB_DIRECTION_IS_HORIZONTAL (direction) && direction != hb_script_get_horizontal_direction (buffer->props.script)) ||
 209       (HB_DIRECTION_IS_VERTICAL   (direction) && direction != HB_DIRECTION_TTB))
 210   {
 211     hb_form_clusters (buffer);
 212     hb_buffer_reverse_clusters (buffer);
 213     buffer->props.direction = HB_DIRECTION_REVERSE (buffer->props.direction);
 214   }
 215 }
 216
 217 static void
 218 hb_reset_glyph_infos (hb_buffer_t *buffer)
 219 {
 220   unsigned int count = buffer->len;
 221   for (unsigned int i = 0; i < count; i++)
 222     buffer->info[i].var1.u32 = buffer->info[i].var2.u32 = 0;
 223 }
 224
 225
 226 /* Substitute */
 227
 228 static void
 229 hb_mirror_chars (hb_ot_shape_context_t *c)
 230 {
 231   hb_unicode_funcs_t *unicode = c->buffer->unicode;
 232
 233   if (HB_DIRECTION_IS_FORWARD (c->target_direction))
 234     return;
 235
 236   hb_mask_t rtlm_mask = c->plan->map.get_1_mask (HB_TAG ('r','t','l','m'));
 237
 238   unsigned int count = c->buffer->len;
 239   for (unsigned int i = 0; i < count; i++) {
 240     hb_codepoint_t codepoint = hb_unicode_mirroring (unicode, c->buffer->info[i].codepoint);
 241     if (likely (codepoint == c->buffer->info[i].codepoint))
 242       c->buffer->info[i].mask |= rtlm_mask; /* XXX this should be moved to before setting user-feature masks */
 243     else
 244       c->buffer->info[i].codepoint = codepoint;
 245   }
 246 }
 247
 248 static void
 249 hb_map_glyphs (hb_font_t    *font,
 250                hb_buffer_t  *buffer)
 251 {
 252   hb_codepoint_t glyph;
 253
 254   if (unlikely (!buffer->len))
 255     return;
 256
 257   buffer->clear_output ();
 258
 259   unsigned int count = buffer->len - 1;
 260   for (buffer->i = 0; buffer->i < count;) {
 261     if (unlikely (is_variation_selector (buffer->info[buffer->i + 1].codepoint))) {
 262       hb_font_get_glyph (font, buffer->info[buffer->i].codepoint, buffer->info[buffer->i + 1].codepoint, &glyph);
 263       buffer->replace_glyph (glyph);
 264       buffer->skip_glyph ();
 265     } else {
 266       hb_font_get_glyph (font, buffer->info[buffer->i].codepoint, 0, &glyph);
 267       buffer->replace_glyph (glyph);
 268     }
 269   }
 270   if (likely (buffer->i < buffer->len)) {
 271     hb_font_get_glyph (font, buffer->info[buffer->i].codepoint, 0, &glyph);
 272     buffer->replace_glyph (glyph);
 273   }
 274   buffer->swap ();
 275 }
 276
 277 static void
 278 hb_substitute_default (hb_ot_shape_context_t *c)
 279 {
 280   hb_map_glyphs (c->font, c->buffer);
 281 }
 282
 283 static void
 284 hb_substitute_complex_fallback (hb_ot_shape_context_t *c HB_UNUSED)
 285 {
 286   /* TODO Arabic */
 287 }
 288
 289
 290 /* Position */
 291
 292 static void
 293 hb_position_default (hb_ot_shape_context_t *c)
 294 {
 295   hb_ot_layout_position_start (c->buffer);
 296
 297   unsigned int count = c->buffer->len;
 298   for (unsigned int i = 0; i < count; i++) {
 299     hb_font_get_glyph_advance_for_direction (c->font, c->buffer->info[i].codepoint,
 300                                              c->buffer->props.direction,
 301                                              &c->buffer->pos[i].x_advance,
 302                                              &c->buffer->pos[i].y_advance);
 303     hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
 304                                                  c->buffer->props.direction,
 305                                                  &c->buffer->pos[i].x_offset,
 306                                                  &c->buffer->pos[i].y_offset);
 307   }
 308 }
 309
 310 static void
 311 hb_position_complex_fallback (hb_ot_shape_context_t *c HB_UNUSED)
 312 {
 313   /* TODO Mark pos */
 314 }
 315
 316 static void
 317 hb_truetype_kern (hb_ot_shape_context_t *c)
 318 {
 319   /* TODO Check for kern=0 */
 320   unsigned int count = c->buffer->len;
 321   for (unsigned int i = 1; i < count; i++) {
 322     hb_position_t x_kern, y_kern, kern1, kern2;
 323     hb_font_get_glyph_kerning_for_direction (c->font,
 324                                              c->buffer->info[i - 1].codepoint, c->buffer->info[i].codepoint,
 325                                              c->buffer->props.direction,
 326                                              &x_kern, &y_kern);
 327
 328     kern1 = x_kern >> 1;
 329     kern2 = x_kern - kern1;
 330     c->buffer->pos[i - 1].x_advance += kern1;
 331     c->buffer->pos[i].x_advance += kern2;
 332     c->buffer->pos[i].x_offset += kern2;
 333
 334     kern1 = y_kern >> 1;
 335     kern2 = y_kern - kern1;
 336     c->buffer->pos[i - 1].y_advance += kern1;
 337     c->buffer->pos[i].y_advance += kern2;
 338     c->buffer->pos[i].y_offset += kern2;
 339   }
 340 }
 341
 342 static void
 343 hb_position_complex_fallback_visual (hb_ot_shape_context_t *c)
 344 {
 345   hb_truetype_kern (c);
 346 }
 347
 348
 349 /* Do it! */
 350
 351 static void
 352 hb_ot_shape_execute_internal (hb_ot_shape_context_t *c)
 353 {
 354   /* Save the original direction, we use it later. */
 355   c->target_direction = c->buffer->props.direction;
 356
 357   hb_reset_glyph_infos (c->buffer); /* BUFFER: Clear buffer var1 and var2 */
 358
 359   hb_set_unicode_props (c->buffer); /* BUFFER: Set general_category and combining_class in var1 */
 360
 361   hb_ensure_native_direction (c->buffer);
 362
 363   _hb_ot_shape_normalize (c);
 364
 365   hb_ot_shape_setup_masks (c); /* BUFFER: Clobbers var2 */
 366
 367   /* SUBSTITUTE */
 368   {
 369     hb_mirror_chars (c);
 370
 371     hb_substitute_default (c);
 372
 373     hb_ot_substitute_complex (c);
 374
 375     if (!c->applied_substitute_complex)
 376       hb_substitute_complex_fallback (c);
 377   }
 378
 379   /* POSITION */
 380   {
 381     hb_position_default (c);
 382
 383     hb_ot_position_complex (c);
 384
 385     hb_bool_t position_fallback = !c->applied_position_complex;
 386     if (position_fallback)
 387       hb_position_complex_fallback (c);
 388
 389     if (HB_DIRECTION_IS_BACKWARD (c->buffer->props.direction))
 390       hb_buffer_reverse (c->buffer);
 391
 392     if (position_fallback)
 393       hb_position_complex_fallback_visual (c);
 394   }
 395
 396   c->buffer->props.direction = c->target_direction;
 397 }
 398
 399 static void
 400 hb_ot_shape_plan_internal (hb_ot_shape_plan_t       *plan,
 401                            hb_face_t                *face,
 402                            const hb_segment_properties_t  *props,
 403                            const hb_feature_t       *user_features,
 404                            unsigned int              num_user_features)
 405 {
 406   hb_ot_shape_planner_t planner;
 407
 408   planner.shaper = hb_ot_shape_complex_categorize (props);
 409
 410   hb_ot_shape_collect_features (&planner, props, user_features, num_user_features);
 411
 412   planner.compile (face, props, *plan);
 413 }
 414
 415 static void
 416 hb_ot_shape_execute (hb_ot_shape_plan_t *plan,
 417                      hb_font_t          *font,
 418                      hb_buffer_t        *buffer,
 419                      const hb_feature_t *user_features,
 420                      unsigned int        num_user_features)
 421 {
 422   hb_ot_shape_context_t c = {plan, font, font->face, buffer, user_features, num_user_features};
 423   hb_ot_shape_execute_internal (&c);
 424 }
 425
 426 void
 427 hb_ot_shape (hb_font_t          *font,
 428              hb_buffer_t        *buffer,
 429              const hb_feature_t *features,
 430              unsigned int        num_features)
 431 {
 432   hb_ot_shape_plan_t plan;
 433
 434   hb_ot_shape_plan_internal (&plan, font->face, &buffer->props, features, num_features);
 435   hb_ot_shape_execute (&plan, font, buffer, features, num_features);
 436 }
 437
 438
 439 HB_END_DECLS