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