src/hb-ot-layout.cc

   1 /*
   2  * Copyright (C) 1998-2004  David Turner and Werner Lemberg
   3  * Copyright (C) 2006  Behdad Esfahbod
   4  * Copyright (C) 2007,2008,2009  Red Hat, Inc.
   5  *
   6  *  This is part of HarfBuzz, an OpenType Layout engine 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): Behdad Esfahbod
  27  */
  28
  29 #define HB_OT_LAYOUT_CC
  30
  31 /* XXX */
  32 #include "hb-buffer-private.h"
  33
  34 #include "hb-ot-layout.h"
  35 #include "hb-ot-layout-private.h"
  36
  37 #include "hb-ot-layout-open-private.h"
  38 #include "hb-ot-layout-gdef-private.h"
  39 #include "hb-ot-layout-gsub-private.h"
  40 #include "hb-ot-layout-gpos-private.h"
  41
  42
  43 #include <stdlib.h>
  44 #include <string.h>
  45
  46
  47 hb_ot_layout_t *
  48 hb_ot_layout_create (void)
  49 {
  50   hb_ot_layout_t *layout = (hb_ot_layout_t *) calloc (1, sizeof (hb_ot_layout_t));
  51
  52   layout->gdef = &Null(GDEF);
  53   layout->gsub = &Null(GSUB);
  54   layout->gpos = &Null(GPOS);
  55
  56   return layout;
  57 }
  58
  59 hb_bool_t
  60 hb_ot_layout_has_substitution (hb_ot_layout_t *layout)
  61 {
  62   return layout->gsub != &Null(GSUB);
  63 }
  64
  65 hb_bool_t
  66 hb_ot_layout_has_positioning (hb_ot_layout_t *layout)
  67 {
  68   return layout->gpos != &Null(GPOS);
  69 }
  70
  71 hb_ot_layout_t *
  72 hb_ot_layout_create_for_data (const char *font_data,
  73                               int         face_index)
  74 {
  75   hb_ot_layout_t *layout;
  76
  77   if (HB_UNLIKELY (font_data == NULL))
  78     return hb_ot_layout_create ();
  79
  80   layout = (hb_ot_layout_t *) calloc (1, sizeof (hb_ot_layout_t));
  81
  82   const OpenTypeFontFile &font = OpenTypeFontFile::get_for_data (font_data);
  83   const OpenTypeFontFace &face = font.get_face (face_index);
  84
  85   layout->gdef = &GDEF::get_for_data (font.get_table_data (face.get_table_by_tag (GDEF::Tag)));
  86   layout->gsub = &GSUB::get_for_data (font.get_table_data (face.get_table_by_tag (GSUB::Tag)));
  87   layout->gpos = &GPOS::get_for_data (font.get_table_data (face.get_table_by_tag (GPOS::Tag)));
  88
  89   return layout;
  90 }
  91
  92 hb_ot_layout_t *
  93 hb_ot_layout_create_for_tables (const char *gdef_data,
  94                                 const char *gsub_data,
  95                                 const char *gpos_data)
  96 {
  97   hb_ot_layout_t *layout;
  98
  99   if (HB_UNLIKELY (gdef_data == NULL && gsub_data == NULL && gpos_data == NULL))
 100     return hb_ot_layout_create ();
 101
 102   layout = (hb_ot_layout_t *) calloc (1, sizeof (hb_ot_layout_t));
 103
 104   layout->gdef = &GDEF::get_for_data (gdef_data);
 105   layout->gsub = &GSUB::get_for_data (gsub_data);
 106   layout->gpos = &GPOS::get_for_data (gpos_data);
 107
 108   return layout;
 109 }
 110
 111 void
 112 hb_ot_layout_destroy (hb_ot_layout_t *layout)
 113 {
 114   free (layout);
 115 }
 116
 117 void
 118 hb_ot_layout_set_direction (hb_ot_layout_t *layout,
 119                             hb_bool_t r2l)
 120 {
 121   layout->gpos_info.r2l = !!r2l;
 122 }
 123
 124 void
 125 hb_ot_layout_set_hinting (hb_ot_layout_t *layout,
 126                           hb_bool_t hinted)
 127 {
 128   layout->gpos_info.dvi = !hinted;
 129 }
 130
 131 void
 132 hb_ot_layout_set_scale (hb_ot_layout_t *layout,
 133                         hb_16dot16_t x_scale, hb_16dot16_t y_scale)
 134 {
 135   layout->gpos_info.x_scale = x_scale;
 136   layout->gpos_info.y_scale = y_scale;
 137 }
 138
 139 void
 140 hb_ot_layout_set_ppem (hb_ot_layout_t *layout,
 141                        unsigned int x_ppem, unsigned int y_ppem)
 142 {
 143   layout->gpos_info.x_ppem = x_ppem;
 144   layout->gpos_info.y_ppem = y_ppem;
 145 }
 146
 147
 148 /*
 149  * GDEF
 150  */
 151
 152 /* TODO the public class_t is a mess */
 153
 154 hb_bool_t
 155 hb_ot_layout_has_font_glyph_classes (hb_ot_layout_t *layout)
 156 {
 157   return layout->gdef->has_glyph_classes ();
 158 }
 159
 160 HB_INTERNAL hb_bool_t
 161 _hb_ot_layout_has_new_glyph_classes (hb_ot_layout_t *layout)
 162 {
 163   return layout->new_gdef.len > 0;
 164 }
 165
 166 HB_INTERNAL unsigned int
 167 _hb_ot_layout_get_glyph_property (hb_ot_layout_t *layout,
 168                                   hb_codepoint_t  glyph)
 169 {
 170   hb_ot_layout_class_t klass;
 171
 172   klass = layout->gdef->get_glyph_class (glyph);
 173
 174   if (!klass && glyph < layout->new_gdef.len)
 175     klass = layout->new_gdef.klasses[glyph];
 176
 177   switch (klass) {
 178   default:
 179   case GDEF::UnclassifiedGlyph: return HB_OT_LAYOUT_GLYPH_CLASS_UNCLASSIFIED;
 180   case GDEF::BaseGlyph:         return HB_OT_LAYOUT_GLYPH_CLASS_BASE_GLYPH;
 181   case GDEF::LigatureGlyph:     return HB_OT_LAYOUT_GLYPH_CLASS_LIGATURE;
 182   case GDEF::ComponentGlyph:    return HB_OT_LAYOUT_GLYPH_CLASS_COMPONENT;
 183   case GDEF::MarkGlyph:
 184         /* TODO old harfbuzz doesn't always parse mark attachments as it says it was
 185          * introduced without a version bump, so it may not be safe */
 186         klass = layout->gdef->get_mark_attachment_type (glyph);
 187         return HB_OT_LAYOUT_GLYPH_CLASS_MARK + (klass << 8);
 188   }
 189 }
 190
 191 HB_INTERNAL hb_bool_t
 192 _hb_ot_layout_check_glyph_property (hb_ot_layout_t  *layout,
 193                                     hb_glyph_info_t *ginfo,
 194                                     unsigned int     lookup_flags,
 195                                     unsigned int    *property_out)
 196 {
 197   unsigned int property;
 198
 199   if (ginfo->gproperty == HB_BUFFER_GLYPH_PROPERTIES_UNKNOWN)
 200     ginfo->gproperty = _hb_ot_layout_get_glyph_property (layout, ginfo->gindex);
 201   property = ginfo->gproperty;
 202   if (property_out)
 203     *property_out = property;
 204
 205   /* Not covered, if, for example, glyph class is ligature and
 206    * lookup_flags includes LookupFlags::IgnoreLigatures
 207    */
 208   if (property & lookup_flags)
 209     return false;
 210
 211   if (property & HB_OT_LAYOUT_GLYPH_CLASS_MARK)
 212   {
 213     /* If using mark filtering sets, the high short of
 214      * lookup_flags has the set index.
 215      */
 216     if (lookup_flags & LookupFlag::UseMarkFilteringSet)
 217       return layout->gdef->mark_set_covers (lookup_flags >> 16, ginfo->gindex);
 218
 219     /* The second byte of lookup_flags has the meaning
 220      * "ignore marks of attachment type different than
 221      * the attachment type specified."
 222      */
 223     if (lookup_flags & LookupFlag::MarkAttachmentType && property & LookupFlag::MarkAttachmentType)
 224       return (lookup_flags & LookupFlag::MarkAttachmentType) == (property & LookupFlag::MarkAttachmentType);
 225   }
 226
 227   return true;
 228 }
 229
 230 HB_INTERNAL hb_bool_t
 231 _hb_ot_layout_skip_mark (hb_ot_layout_t  *layout,
 232                          hb_glyph_info_t *ginfo,
 233                          unsigned int     lookup_flags,
 234                          unsigned int    *property_out)
 235 {
 236   unsigned int property;
 237
 238   if (ginfo->gproperty == HB_BUFFER_GLYPH_PROPERTIES_UNKNOWN)
 239     ginfo->gproperty = _hb_ot_layout_get_glyph_property (layout, ginfo->gindex);
 240   property = ginfo->gproperty;
 241   if (property_out)
 242     *property_out = property;
 243
 244   if (property & HB_OT_LAYOUT_GLYPH_CLASS_MARK)
 245   {
 246     /* Skip mark if lookup_flags includes LookupFlags::IgnoreMarks */
 247     if (lookup_flags & LookupFlag::IgnoreMarks)
 248       return true;
 249
 250     /* If using mark filtering sets, the high short of lookup_flags has the set index. */
 251     if (lookup_flags & LookupFlag::UseMarkFilteringSet)
 252       return !layout->gdef->mark_set_covers (lookup_flags >> 16, ginfo->gindex);
 253
 254     /* The second byte of lookup_flags has the meaning "ignore marks of attachment type
 255      * different than the attachment type specified." */
 256     if (lookup_flags & LookupFlag::MarkAttachmentType && property & LookupFlag::MarkAttachmentType)
 257       return (lookup_flags & LookupFlag::MarkAttachmentType) != (property & LookupFlag::MarkAttachmentType);
 258   }
 259
 260   return false;
 261 }
 262
 263 HB_INTERNAL void
 264 _hb_ot_layout_set_glyph_property (hb_ot_layout_t *layout,
 265                                   hb_codepoint_t  glyph,
 266                                   unsigned int    property)
 267 { hb_ot_layout_set_glyph_class (layout, glyph, (hb_ot_layout_glyph_class_t) (property & 0xff)); }
 268
 269
 270 hb_ot_layout_glyph_class_t
 271 hb_ot_layout_get_glyph_class (hb_ot_layout_t *layout,
 272                               hb_codepoint_t  glyph)
 273 { return (hb_ot_layout_glyph_class_t) (_hb_ot_layout_get_glyph_property (layout, glyph) & 0xff); }
 274
 275 void
 276 hb_ot_layout_set_glyph_class (hb_ot_layout_t             *layout,
 277                               hb_codepoint_t              glyph,
 278                               hb_ot_layout_glyph_class_t  klass)
 279 {
 280   /* TODO optimize this, similar to old harfbuzz code for example */
 281
 282   hb_ot_layout_class_t gdef_klass;
 283   int len = layout->new_gdef.len;
 284
 285   if (HB_UNLIKELY (glyph > 65535))
 286     return;
 287
 288   if (glyph >= len) {
 289     int new_len;
 290     unsigned char *new_klasses;
 291
 292     new_len = len == 0 ? 120 : 2 * len;
 293     if (new_len > 65535)
 294       new_len = 65535;
 295     new_klasses = (unsigned char *) realloc (layout->new_gdef.klasses, new_len * sizeof (unsigned char));
 296
 297     if (HB_UNLIKELY (!new_klasses))
 298       return;
 299
 300     memset (new_klasses + len, 0, new_len - len);
 301
 302     layout->new_gdef.klasses = new_klasses;
 303     layout->new_gdef.len = new_len;
 304   }
 305
 306   switch (klass) {
 307   default:
 308   case HB_OT_LAYOUT_GLYPH_CLASS_UNCLASSIFIED:   gdef_klass = GDEF::UnclassifiedGlyph;   break;
 309   case HB_OT_LAYOUT_GLYPH_CLASS_BASE_GLYPH:     gdef_klass = GDEF::BaseGlyph;           break;
 310   case HB_OT_LAYOUT_GLYPH_CLASS_LIGATURE:       gdef_klass = GDEF::LigatureGlyph;       break;
 311   case HB_OT_LAYOUT_GLYPH_CLASS_MARK:           gdef_klass = GDEF::MarkGlyph;           break;
 312   case HB_OT_LAYOUT_GLYPH_CLASS_COMPONENT:      gdef_klass = GDEF::ComponentGlyph;      break;
 313   }
 314
 315   layout->new_gdef.klasses[glyph] = gdef_klass;
 316   return;
 317 }
 318
 319 void
 320 hb_ot_layout_build_glyph_classes (hb_ot_layout_t *layout,
 321                                   uint16_t        num_total_glyphs,
 322                                   hb_codepoint_t *glyphs,
 323                                   unsigned char  *klasses,
 324                                   uint16_t        count)
 325 {
 326   if (HB_UNLIKELY (!count || !glyphs || !klasses))
 327     return;
 328
 329   if (layout->new_gdef.len == 0) {
 330     layout->new_gdef.klasses = (unsigned char *) calloc (num_total_glyphs, sizeof (unsigned char));
 331     layout->new_gdef.len = count;
 332   }
 333
 334   for (unsigned int i = 0; i < count; i++)
 335     hb_ot_layout_set_glyph_class (layout, glyphs[i], (hb_ot_layout_glyph_class_t) klasses[i]);
 336 }
 337
 338 hb_bool_t
 339 hb_ot_layout_get_attach_points (hb_ot_layout_t *layout,
 340                                 hb_codepoint_t  glyph,
 341                                 unsigned int   *point_count /* IN/OUT */,
 342                                 unsigned int   *point_array /* OUT */)
 343 {
 344   return layout->gdef->get_attach_points (glyph, point_count, point_array);
 345 }
 346
 347 hb_bool_t
 348 hb_ot_layout_get_lig_carets (hb_ot_layout_t *layout,
 349                              hb_codepoint_t  glyph,
 350                              unsigned int   *caret_count /* IN/OUT */,
 351                              int            *caret_array /* OUT */)
 352 {
 353   return layout->gdef->get_lig_carets (layout, glyph, caret_count, caret_array);
 354 }
 355
 356 /*
 357  * GSUB/GPOS
 358  */
 359
 360 static const GSUBGPOS&
 361 get_gsubgpos_table (hb_ot_layout_t            *layout,
 362                     hb_ot_layout_table_type_t  table_type)
 363 {
 364   switch (table_type) {
 365     case HB_OT_LAYOUT_TABLE_TYPE_GSUB: return *(layout->gsub);
 366     case HB_OT_LAYOUT_TABLE_TYPE_GPOS: return *(layout->gpos);
 367     default:                           return Null(GSUBGPOS);
 368   }
 369 }
 370
 371
 372 unsigned int
 373 hb_ot_layout_table_get_script_count (hb_ot_layout_t            *layout,
 374                                      hb_ot_layout_table_type_t  table_type)
 375 {
 376   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 377
 378   return g.get_script_count ();
 379 }
 380
 381 hb_tag_t
 382 hb_ot_layout_table_get_script_tag (hb_ot_layout_t            *layout,
 383                                    hb_ot_layout_table_type_t  table_type,
 384                                    unsigned int               script_index)
 385 {
 386   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 387
 388   return g.get_script_tag (script_index);
 389 }
 390
 391 hb_bool_t
 392 hb_ot_layout_table_find_script (hb_ot_layout_t            *layout,
 393                                 hb_ot_layout_table_type_t  table_type,
 394                                 hb_tag_t                   script_tag,
 395                                 unsigned int              *script_index)
 396 {
 397   ASSERT_STATIC (NO_INDEX == HB_OT_LAYOUT_NO_SCRIPT_INDEX);
 398   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 399
 400   if (g.find_script_index (script_tag, script_index))
 401     return TRUE;
 402
 403   /* try finding 'DFLT' */
 404   if (g.find_script_index (HB_OT_LAYOUT_TAG_DEFAULT_SCRIPT, script_index))
 405     return FALSE;
 406
 407   /* try with 'dflt'; MS site has had typos and many fonts use it now :( */
 408   if (g.find_script_index (HB_OT_LAYOUT_TAG_DEFAULT_LANGUAGE, script_index))
 409     return FALSE;
 410
 411   if (script_index) *script_index = HB_OT_LAYOUT_NO_SCRIPT_INDEX;
 412   return FALSE;
 413 }
 414
 415 unsigned int
 416 hb_ot_layout_table_get_feature_count (hb_ot_layout_t            *layout,
 417                                       hb_ot_layout_table_type_t  table_type)
 418 {
 419   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 420
 421   return g.get_feature_count ();
 422 }
 423
 424 hb_tag_t
 425 hb_ot_layout_table_get_feature_tag (hb_ot_layout_t            *layout,
 426                                     hb_ot_layout_table_type_t  table_type,
 427                                     unsigned int               feature_index)
 428 {
 429   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 430
 431   return g.get_feature_tag (feature_index);
 432 }
 433
 434 hb_bool_t
 435 hb_ot_layout_table_find_feature (hb_ot_layout_t            *layout,
 436                                  hb_ot_layout_table_type_t  table_type,
 437                                  hb_tag_t                   feature_tag,
 438                                  unsigned int              *feature_index)
 439 {
 440   ASSERT_STATIC (NO_INDEX == HB_OT_LAYOUT_NO_FEATURE_INDEX);
 441   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 442
 443   if (g.find_feature_index (feature_tag, feature_index))
 444     return TRUE;
 445
 446   if (feature_index) *feature_index = HB_OT_LAYOUT_NO_FEATURE_INDEX;
 447   return FALSE;
 448 }
 449
 450 unsigned int
 451 hb_ot_layout_table_get_lookup_count (hb_ot_layout_t            *layout,
 452                                      hb_ot_layout_table_type_t  table_type)
 453 {
 454   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 455
 456   return g.get_lookup_count ();
 457 }
 458
 459
 460 unsigned int
 461 hb_ot_layout_script_get_language_count (hb_ot_layout_t            *layout,
 462                                         hb_ot_layout_table_type_t  table_type,
 463                                         unsigned int               script_index)
 464 {
 465   const Script &s = get_gsubgpos_table (layout, table_type).get_script (script_index);
 466
 467   return s.get_lang_sys_count ();
 468 }
 469
 470 hb_tag_t
 471 hb_ot_layout_script_get_language_tag (hb_ot_layout_t            *layout,
 472                                       hb_ot_layout_table_type_t  table_type,
 473                                       unsigned int               script_index,
 474                                       unsigned int               language_index)
 475 {
 476   const Script &s = get_gsubgpos_table (layout, table_type).get_script (script_index);
 477
 478   return s.get_lang_sys_tag (language_index);
 479 }
 480
 481 hb_bool_t
 482 hb_ot_layout_script_find_language (hb_ot_layout_t            *layout,
 483                                    hb_ot_layout_table_type_t  table_type,
 484                                    unsigned int               script_index,
 485                                    hb_tag_t                   language_tag,
 486                                    unsigned int              *language_index)
 487 {
 488   ASSERT_STATIC (NO_INDEX == HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX);
 489   const Script &s = get_gsubgpos_table (layout, table_type).get_script (script_index);
 490
 491   if (s.find_lang_sys_index (language_tag, language_index))
 492     return TRUE;
 493
 494   /* try with 'dflt'; MS site has had typos and many fonts use it now :( */
 495   if (s.find_lang_sys_index (HB_OT_LAYOUT_TAG_DEFAULT_LANGUAGE, language_index))
 496     return FALSE;
 497
 498   if (language_index) *language_index = HB_OT_LAYOUT_DEFAULT_LANGUAGE_INDEX;
 499   return FALSE;
 500 }
 501
 502 hb_bool_t
 503 hb_ot_layout_language_get_required_feature_index (hb_ot_layout_t            *layout,
 504                                                   hb_ot_layout_table_type_t  table_type,
 505                                                   unsigned int               script_index,
 506                                                   unsigned int               language_index,
 507                                                   unsigned int              *feature_index)
 508 {
 509   const LangSys &l = get_gsubgpos_table (layout, table_type).get_script (script_index).get_lang_sys (language_index);
 510
 511   if (feature_index) *feature_index = l.get_required_feature_index ();
 512
 513   return l.has_required_feature ();
 514 }
 515
 516 unsigned int
 517 hb_ot_layout_language_get_feature_count (hb_ot_layout_t            *layout,
 518                                          hb_ot_layout_table_type_t  table_type,
 519                                          unsigned int               script_index,
 520                                          unsigned int               language_index)
 521 {
 522   const LangSys &l = get_gsubgpos_table (layout, table_type).get_script (script_index).get_lang_sys (language_index);
 523
 524   return l.get_feature_count ();
 525 }
 526
 527 unsigned int
 528 hb_ot_layout_language_get_feature_index (hb_ot_layout_t            *layout,
 529                                          hb_ot_layout_table_type_t  table_type,
 530                                          unsigned int               script_index,
 531                                          unsigned int               language_index,
 532                                          unsigned int               num_feature)
 533 {
 534   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 535   const LangSys &l = g.get_script (script_index).get_lang_sys (language_index);
 536
 537   return l.get_feature_index (num_feature);
 538 }
 539
 540 hb_tag_t
 541 hb_ot_layout_language_get_feature_tag (hb_ot_layout_t            *layout,
 542                                        hb_ot_layout_table_type_t  table_type,
 543                                        unsigned int               script_index,
 544                                        unsigned int               language_index,
 545                                        unsigned int               num_feature)
 546 {
 547   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 548   const LangSys &l = g.get_script (script_index).get_lang_sys (language_index);
 549   unsigned int feature_index = l.get_feature_index (num_feature);
 550
 551   return g.get_feature_tag (feature_index);
 552 }
 553
 554
 555 hb_bool_t
 556 hb_ot_layout_language_find_feature (hb_ot_layout_t            *layout,
 557                                     hb_ot_layout_table_type_t  table_type,
 558                                     unsigned int               script_index,
 559                                     unsigned int               language_index,
 560                                     hb_tag_t                   feature_tag,
 561                                     unsigned int              *feature_index)
 562 {
 563   ASSERT_STATIC (NO_INDEX == HB_OT_LAYOUT_NO_FEATURE_INDEX);
 564   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 565   const LangSys &l = g.get_script (script_index).get_lang_sys (language_index);
 566
 567   unsigned int num_features = l.get_feature_count ();
 568   for (unsigned int i = 0; i < num_features; i++) {
 569     unsigned int f_index = l.get_feature_index (i);
 570
 571     if (feature_tag == g.get_feature_tag (f_index)) {
 572       if (feature_index) *feature_index = f_index;
 573       return TRUE;
 574     }
 575   }
 576
 577   if (feature_index) *feature_index = HB_OT_LAYOUT_NO_FEATURE_INDEX;
 578   return FALSE;
 579 }
 580
 581 unsigned int
 582 hb_ot_layout_feature_get_lookup_count (hb_ot_layout_t            *layout,
 583                                        hb_ot_layout_table_type_t  table_type,
 584                                        unsigned int               feature_index)
 585 {
 586   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 587   const Feature &f = g.get_feature (feature_index);
 588
 589   return f.get_lookup_count ();
 590 }
 591
 592 unsigned int
 593 hb_ot_layout_feature_get_lookup_index (hb_ot_layout_t            *layout,
 594                                        hb_ot_layout_table_type_t  table_type,
 595                                        unsigned int               feature_index,
 596                                        unsigned int               num_lookup)
 597 {
 598   const GSUBGPOS &g = get_gsubgpos_table (layout, table_type);
 599   const Feature &f = g.get_feature (feature_index);
 600
 601   return f.get_lookup_index (num_lookup);
 602 }
 603
 604 /*
 605  * GSUB
 606  */
 607
 608 hb_bool_t
 609 hb_ot_layout_substitute_lookup (hb_ot_layout_t              *layout,
 610                                 hb_buffer_t                 *buffer,
 611                                 unsigned int                 lookup_index,
 612                                 hb_ot_layout_feature_mask_t  mask)
 613 {
 614   return layout->gsub->substitute_lookup (layout, buffer, lookup_index, mask);
 615 }
 616
 617 /*
 618  * GPOS
 619  */
 620
 621 hb_bool_t
 622 hb_ot_layout_position_lookup   (hb_ot_layout_t              *layout,
 623                                 hb_buffer_t                 *buffer,
 624                                 unsigned int                 lookup_index,
 625                                 hb_ot_layout_feature_mask_t  mask)
 626 {
 627   return layout->gpos->position_lookup (layout, buffer, lookup_index, mask);
 628 }