src/hb-ot-layout-gsubgpos-private.h

   1 /*
   2  * Copyright (C) 2007,2008,2009  Red Hat, Inc.
   3  *
   4  *  This is part of HarfBuzz, an OpenType Layout engine library.
   5  *
   6  * Permission is hereby granted, without written agreement and without
   7  * license or royalty fees, to use, copy, modify, and distribute this
   8  * software and its documentation for any purpose, provided that the
   9  * above copyright notice and the following two paragraphs appear in
  10  * all copies of this software.
  11  *
  12  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  13  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  14  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  15  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  16  * DAMAGE.
  17  *
  18  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  19  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  20  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  21  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  22  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  23  *
  24  * Red Hat Author(s): Behdad Esfahbod
  25  */
  26
  27 #ifndef HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H
  28 #define HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H
  29
  30 #include "hb-ot-layout-gdef-private.h"
  31 #include "harfbuzz-buffer-private.h" /* XXX */
  32
  33
  34 #define LOOKUP_ARGS_DEF \
  35         hb_ot_layout_t *layout, \
  36         hb_buffer_t    *buffer, \
  37         unsigned int    context_length HB_GNUC_UNUSED, \
  38         unsigned int    nesting_level_left HB_GNUC_UNUSED, \
  39         unsigned int    lookup_flag, \
  40         unsigned int    property HB_GNUC_UNUSED /* propety of first glyph */
  41 #define LOOKUP_ARGS \
  42         layout, \
  43         buffer, \
  44         context_length, \
  45         nesting_level_left, \
  46         lookup_flag, \
  47         property
  48
  49
  50 typedef bool (*match_func_t) (hb_codepoint_t glyph_id, const USHORT &value, char *data);
  51 typedef bool (*apply_lookup_func_t) (LOOKUP_ARGS_DEF, unsigned int lookup_index);
  52
  53 struct ContextFuncs {
  54   match_func_t match;
  55   apply_lookup_func_t apply;
  56 };
  57
  58
  59 static inline bool match_glyph (hb_codepoint_t glyph_id, const USHORT &value, char *data) {
  60   return glyph_id == value;
  61 }
  62
  63 static inline bool match_class (hb_codepoint_t glyph_id, const USHORT &value, char *data) {
  64   const ClassDef &class_def = * (const ClassDef *) data;
  65   return class_def.get_class (glyph_id) == value;
  66 }
  67
  68 static inline bool match_coverage (hb_codepoint_t glyph_id, const USHORT &value, char *data) {
  69   const OffsetTo<Coverage> &coverage = * (const OffsetTo<Coverage> *) &value;
  70   return (data+coverage) (glyph_id) != NOT_COVERED;
  71 }
  72
  73
  74 static inline bool match_input (LOOKUP_ARGS_DEF,
  75                                 unsigned int count, /* Including the first glyph (not matched) */
  76                                 const USHORT input[], /* Array of input values--start with second glyph */
  77                                 match_func_t match_func,
  78                                 char *match_data,
  79                                 unsigned int *context_length_out)
  80 {
  81   unsigned int i, j;
  82   unsigned int end = MIN (buffer->in_length, buffer->in_pos + context_length);
  83   if (HB_UNLIKELY (buffer->in_pos + count > end))
  84     return false;
  85
  86   for (i = 1, j = buffer->in_pos + 1; i < count; i++, j++) {
  87     while (!_hb_ot_layout_check_glyph_property (layout, IN_ITEM (j), lookup_flag, &property)) {
  88       if (HB_UNLIKELY (j + count - i == end))
  89         return false;
  90       j++;
  91     }
  92
  93     if (HB_LIKELY (!match_func (IN_GLYPH(j), input[i - 1], match_data)))
  94       return false;
  95   }
  96
  97   *context_length_out = j - buffer->in_pos;
  98
  99   return true;
 100 }
 101
 102 static inline bool match_backtrack (LOOKUP_ARGS_DEF,
 103                                     unsigned int count,
 104                                     const USHORT backtrack[],
 105                                     match_func_t match_func,
 106                                     char *match_data)
 107 {
 108   if (HB_UNLIKELY (buffer->out_pos < count))
 109     return false;
 110
 111   for (unsigned int i = 0, j = buffer->out_pos - 1; i < count; i++, j--) {
 112     while (!_hb_ot_layout_check_glyph_property (layout, OUT_ITEM (j), lookup_flag, &property)) {
 113       if (HB_UNLIKELY (j + 1 == count - i))
 114         return false;
 115       j--;
 116     }
 117
 118     if (HB_LIKELY (!match_func (OUT_GLYPH(j), backtrack[i], match_data)))
 119       return false;
 120   }
 121
 122   return true;
 123 }
 124
 125 static inline bool match_lookahead (LOOKUP_ARGS_DEF,
 126                                     unsigned int count,
 127                                     const USHORT lookahead[],
 128                                     match_func_t match_func,
 129                                     char *match_data,
 130                                     unsigned int offset)
 131 {
 132   unsigned int i, j;
 133   unsigned int end = MIN (buffer->in_length, buffer->in_pos + context_length);
 134   if (HB_UNLIKELY (buffer->in_pos + offset + count > end))
 135     return false;
 136
 137   for (i = 0, j = buffer->in_pos + offset; i < count; i++, j++) {
 138     while (!_hb_ot_layout_check_glyph_property (layout, OUT_ITEM (j), lookup_flag, &property)) {
 139       if (HB_UNLIKELY (j + count - i == end))
 140         return false;
 141       j++;
 142     }
 143
 144     if (HB_LIKELY (!match_func (IN_GLYPH(j), lookahead[i], match_data)))
 145       return false;
 146   }
 147
 148   return true;
 149 }
 150
 151
 152 struct LookupRecord {
 153
 154   USHORT        sequenceIndex;          /* Index into current glyph
 155                                          * sequence--first glyph = 0 */
 156   USHORT        lookupListIndex;        /* Lookup to apply to that
 157                                          * position--zero--based */
 158 };
 159 ASSERT_SIZE (LookupRecord, 4);
 160
 161 static inline bool apply_lookup (LOOKUP_ARGS_DEF,
 162                                  unsigned int count, /* Including the first glyph */
 163                                  unsigned int lookupCount,
 164                                  const LookupRecord lookupRecord[], /* Array of LookupRecords--in design order */
 165                                  apply_lookup_func_t apply_func)
 166 {
 167   unsigned int record_count = lookupCount;
 168   const LookupRecord *record = lookupRecord;
 169
 170   /* XXX We have to jump non-matching glyphs when applying too, right? */
 171   /* TODO We don't support lookupRecord arrays that are not increasing:
 172    *      Should be easy for in_place ones at least. */
 173   for (unsigned int i = 0; i < count;)
 174   {
 175     if (record_count && i == record->sequenceIndex)
 176     {
 177       unsigned int old_pos = buffer->in_pos;
 178
 179       /* Apply a lookup */
 180       bool done = apply_func (LOOKUP_ARGS, record->lookupListIndex);
 181
 182       record++;
 183       record_count--;
 184       i += buffer->in_pos - old_pos;
 185
 186       if (!done)
 187         goto not_applied;
 188     }
 189     else
 190     {
 191     not_applied:
 192       /* No lookup applied for this index */
 193       _hb_buffer_next_glyph (buffer);
 194       i++;
 195     }
 196   }
 197
 198   return true;
 199 }
 200
 201
 202 /* Contextual lookups */
 203
 204 struct ContextLookupContext {
 205   ContextFuncs funcs;
 206   char *match_data;
 207 };
 208
 209 static inline bool context_lookup (LOOKUP_ARGS_DEF,
 210                                    unsigned int inputCount, /* Including the first glyph (not matched) */
 211                                    const USHORT input[], /* Array of input values--start with second glyph */
 212                                    unsigned int lookupCount,
 213                                    const LookupRecord lookupRecord[],
 214                                    ContextLookupContext &context)
 215 {
 216   /* First guess */
 217   if (HB_UNLIKELY (buffer->in_pos + inputCount > buffer->in_length ||
 218                    context_length < inputCount))
 219     return false;
 220
 221   return match_input (LOOKUP_ARGS,
 222                       inputCount, input,
 223                       context.funcs.match, context.match_data,
 224                       &context_length) &&
 225          apply_lookup (LOOKUP_ARGS,
 226                        inputCount,
 227                        lookupCount, lookupRecord,
 228                        context.funcs.apply);
 229 }
 230
 231 struct Rule {
 232
 233   friend struct RuleSet;
 234
 235   private:
 236   inline bool apply (LOOKUP_ARGS_DEF, ContextLookupContext &context) const {
 237     const LookupRecord *lookupRecord = (const LookupRecord *)
 238                                        ((const char *) input +
 239                                         sizeof (input[0]) * (inputCount ? inputCount - 1 : 0));
 240     return context_lookup (LOOKUP_ARGS,
 241                            inputCount,
 242                            input,
 243                            lookupCount,
 244                            lookupRecord,
 245                            context);
 246   }
 247
 248   private:
 249   USHORT        inputCount;             /* Total number of glyphs in input
 250                                          * glyph sequence--includes the  first
 251                                          * glyph */
 252   USHORT        lookupCount;            /* Number of LookupRecords */
 253   USHORT        input[];                /* Array of match inputs--start with
 254                                          * second glyph */
 255   LookupRecord  lookupRecordX[];        /* Array of LookupRecords--in
 256                                          * design order */
 257 };
 258 ASSERT_SIZE (Rule, 4);
 259
 260 struct RuleSet {
 261
 262   inline bool apply (LOOKUP_ARGS_DEF, ContextLookupContext &context) const {
 263
 264     unsigned int num_rules = rule.len;
 265     for (unsigned int i = 0; i < num_rules; i++) {
 266       if ((this+rule[i]).apply (LOOKUP_ARGS, context))
 267         return true;
 268     }
 269
 270     return false;
 271   }
 272
 273   private:
 274   OffsetArrayOf<Rule>
 275                 rule;                   /* Array of Rule tables
 276                                          * ordered by preference */
 277 };
 278
 279
 280 struct ContextFormat1 {
 281
 282   friend struct Context;
 283
 284   private:
 285   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 286
 287     unsigned int index = (this+coverage) (IN_CURGLYPH ());
 288     if (G_LIKELY (index == NOT_COVERED))
 289       return false;
 290
 291     const RuleSet &rule_set = this+ruleSet[index];
 292     struct ContextLookupContext context = {
 293       {match_glyph, apply_func},
 294       NULL
 295     };
 296     return rule_set.apply (LOOKUP_ARGS, context);
 297   }
 298
 299   private:
 300   USHORT        format;                 /* Format identifier--format = 1 */
 301   OffsetTo<Coverage>
 302                 coverage;               /* Offset to Coverage table--from
 303                                          * beginning of table */
 304   OffsetArrayOf<RuleSet>
 305                 ruleSet;                /* Array of RuleSet tables
 306                                          * ordered by Coverage Index */
 307 };
 308 ASSERT_SIZE (ContextFormat1, 6);
 309
 310
 311 struct ContextFormat2 {
 312
 313   friend struct Context;
 314
 315   private:
 316   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 317
 318     unsigned int index = (this+coverage) (IN_CURGLYPH ());
 319     if (G_LIKELY (index == NOT_COVERED))
 320       return false;
 321
 322     const ClassDef &class_def = this+classDef;
 323     index = class_def (IN_CURGLYPH ());
 324     const RuleSet &rule_set = this+ruleSet[index];
 325     /* LONGTERMTODO: Old code fetches glyph classes at most once and caches
 326      * them across subrule lookups.  Not sure it's worth it.
 327      */
 328     struct ContextLookupContext context = {
 329      {match_class, apply_func},
 330       (char *) &class_def
 331     };
 332     return rule_set.apply (LOOKUP_ARGS, context);
 333   }
 334
 335   private:
 336   USHORT        format;                 /* Format identifier--format = 2 */
 337   OffsetTo<Coverage>
 338                 coverage;               /* Offset to Coverage table--from
 339                                          * beginning of table */
 340   OffsetTo<ClassDef>
 341                 classDef;               /* Offset to glyph ClassDef table--from
 342                                          * beginning of table */
 343   OffsetArrayOf<RuleSet>
 344                 ruleSet;                /* Array of RuleSet tables
 345                                          * ordered by class */
 346 };
 347 ASSERT_SIZE (ContextFormat2, 8);
 348
 349
 350 struct ContextFormat3 {
 351
 352   friend struct Context;
 353
 354   private:
 355   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 356
 357     unsigned int index = (this+coverage[0]) (IN_CURGLYPH ());
 358     if (G_LIKELY (index == NOT_COVERED))
 359       return false;
 360
 361     const LookupRecord *lookupRecord = (const LookupRecord *)
 362                                        ((const char *) coverage +
 363                                         sizeof (coverage[0]) * glyphCount);
 364     struct ContextLookupContext context = {
 365       {match_coverage, apply_func},
 366       (char *) this
 367     };
 368     return context_lookup (LOOKUP_ARGS,
 369                            glyphCount,
 370                            (const USHORT *) (coverage + 1),
 371                            lookupCount,
 372                            lookupRecord,
 373                            context);
 374   }
 375
 376   private:
 377   USHORT        format;                 /* Format identifier--format = 3 */
 378   USHORT        glyphCount;             /* Number of glyphs in the input glyph
 379                                          * sequence */
 380   USHORT        lookupCount;            /* Number of LookupRecords */
 381   OffsetTo<Coverage>
 382                 coverage[];             /* Array of offsets to Coverage
 383                                          * table in glyph sequence order */
 384   LookupRecord  lookupRecordX[];        /* Array of LookupRecords--in
 385                                          * design order */
 386 };
 387 ASSERT_SIZE (ContextFormat3, 6);
 388
 389 struct Context {
 390
 391   protected:
 392   bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 393     switch (u.format) {
 394     case 1: return u.format1->apply (LOOKUP_ARGS, apply_func);
 395     case 2: return u.format2->apply (LOOKUP_ARGS, apply_func);
 396     case 3: return u.format3->apply (LOOKUP_ARGS, apply_func);
 397     default:return false;
 398     }
 399   }
 400
 401   private:
 402   union {
 403   USHORT                format;         /* Format identifier */
 404   ContextFormat1        format1[];
 405   ContextFormat2        format2[];
 406   ContextFormat3        format3[];
 407   } u;
 408 };
 409 ASSERT_SIZE (Context, 2);
 410
 411
 412 /* Chaining Contextual lookups */
 413
 414 struct ChainContextLookupContext {
 415   ContextFuncs funcs;
 416   char *match_data[3];
 417 };
 418
 419 static inline bool chain_context_lookup (LOOKUP_ARGS_DEF,
 420                                          unsigned int backtrackCount,
 421                                          const USHORT backtrack[],
 422                                          unsigned int inputCount, /* Including the first glyph (not matched) */
 423                                          const USHORT input[], /* Array of input values--start with second glyph */
 424                                          unsigned int lookaheadCount,
 425                                          const USHORT lookahead[],
 426                                          unsigned int lookupCount,
 427                                          const LookupRecord lookupRecord[],
 428                                          ChainContextLookupContext &context)
 429 {
 430   /* First guess */
 431   if (HB_UNLIKELY (buffer->out_pos < backtrackCount ||
 432                    buffer->in_pos + inputCount + lookaheadCount > buffer->in_length))
 433     return false;
 434
 435   unsigned int offset;
 436   return match_backtrack (LOOKUP_ARGS,
 437                           backtrackCount, backtrack,
 438                           context.funcs.match, context.match_data[0]) &&
 439          match_input (LOOKUP_ARGS,
 440                       inputCount, input,
 441                       context.funcs.match, context.match_data[1],
 442                       &offset) &&
 443          match_lookahead (LOOKUP_ARGS,
 444                           lookaheadCount, lookahead,
 445                           context.funcs.match, context.match_data[2],
 446                           offset) &&
 447          (context_length = offset, true) &&
 448          apply_lookup (LOOKUP_ARGS,
 449                        inputCount,
 450                        lookupCount, lookupRecord,
 451                        context.funcs.apply);
 452 }
 453
 454 struct ChainRule {
 455
 456   friend struct ChainRuleSet;
 457
 458   private:
 459   inline bool apply (LOOKUP_ARGS_DEF, ChainContextLookupContext &context) const {
 460     const HeadlessArrayOf<USHORT> &input = * (const HeadlessArrayOf<USHORT> *)
 461                                              ((const char *) &backtrack + backtrack.get_size ());
 462     const ArrayOf<USHORT> &lookahead = * (const ArrayOf<USHORT> *)
 463                                          ((const char *) &input + input.get_size ());
 464     const ArrayOf<LookupRecord> &lookup = * (const ArrayOf<LookupRecord> *)
 465                                             ((const char *) &lookahead + lookahead.get_size ());
 466     return chain_context_lookup (LOOKUP_ARGS,
 467                                  backtrack.len,
 468                                  backtrack.array,
 469                                  input.len,
 470                                  input.array + 1,
 471                                  lookahead.len,
 472                                  lookahead.array,
 473                                  lookup.len,
 474                                  lookup.array,
 475                                  context);
 476     return false;
 477   }
 478
 479
 480   private:
 481   ArrayOf<USHORT>
 482                 backtrack;              /* Array of backtracking values
 483                                          * (to be matched before the input
 484                                          * sequence) */
 485   HeadlessArrayOf<USHORT>
 486                 inputX;                 /* Array of input values (start with
 487                                          * second glyph) */
 488   ArrayOf<USHORT>
 489                 lookaheadX;             /* Array of lookahead values's (to be
 490                                          * matched after the input sequence) */
 491   ArrayOf<LookupRecord>
 492                 lookupX;                /* Array of LookupRecords--in
 493                                          * design order) */
 494 };
 495 ASSERT_SIZE (ChainRule, 8);
 496
 497 struct ChainRuleSet {
 498
 499   inline bool apply (LOOKUP_ARGS_DEF, ChainContextLookupContext &context) const {
 500
 501     unsigned int num_rules = rule.len;
 502     for (unsigned int i = 0; i < num_rules; i++) {
 503       if ((this+rule[i]).apply (LOOKUP_ARGS, context))
 504         return true;
 505     }
 506
 507     return false;
 508   }
 509
 510   private:
 511   OffsetArrayOf<ChainRule>
 512                 rule;                   /* Array of ChainRule tables
 513                                          * ordered by preference */
 514 };
 515 ASSERT_SIZE (ChainRuleSet, 2);
 516
 517 struct ChainContextFormat1 {
 518
 519   friend struct ChainContext;
 520
 521   private:
 522   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 523
 524     unsigned int index = (this+coverage) (IN_CURGLYPH ());
 525     if (G_LIKELY (index == NOT_COVERED))
 526       return false;
 527
 528     const ChainRuleSet &rule_set = this+ruleSet[index];
 529     struct ChainContextLookupContext context = {
 530       {match_glyph, apply_func},
 531       {NULL, NULL, NULL}
 532     };
 533     return rule_set.apply (LOOKUP_ARGS, context);
 534   }
 535   private:
 536   USHORT        format;                 /* Format identifier--format = 1 */
 537   OffsetTo<Coverage>
 538                 coverage;               /* Offset to Coverage table--from
 539                                          * beginning of table */
 540   OffsetArrayOf<ChainRuleSet>
 541                 ruleSet;                /* Array of ChainRuleSet tables
 542                                          * ordered by Coverage Index */
 543 };
 544 ASSERT_SIZE (ChainContextFormat1, 6);
 545
 546 struct ChainContextFormat2 {
 547
 548   friend struct ChainContext;
 549
 550   private:
 551   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 552
 553     unsigned int index = (this+coverage) (IN_CURGLYPH ());
 554     if (G_LIKELY (index == NOT_COVERED))
 555       return false;
 556
 557     const ClassDef &backtrack_class_def = this+backtrackClassDef;
 558     const ClassDef &input_class_def = this+inputClassDef;
 559     const ClassDef &lookahead_class_def = this+lookaheadClassDef;
 560
 561     index = input_class_def (IN_CURGLYPH ());
 562     const ChainRuleSet &rule_set = this+ruleSet[index];
 563     /* LONGTERMTODO: Old code fetches glyph classes at most once and caches
 564      * them across subrule lookups.  Not sure it's worth it.
 565      */
 566     struct ChainContextLookupContext context = {
 567      {match_class, apply_func},
 568      {(char *) &backtrack_class_def,
 569       (char *) &input_class_def,
 570       (char *) &lookahead_class_def}
 571     };
 572     return rule_set.apply (LOOKUP_ARGS, context);
 573   }
 574
 575   private:
 576   USHORT        format;                 /* Format identifier--format = 2 */
 577   OffsetTo<Coverage>
 578                 coverage;               /* Offset to Coverage table--from
 579                                          * beginning of table */
 580   OffsetTo<ClassDef>
 581                 backtrackClassDef;      /* Offset to glyph ClassDef table
 582                                          * containing backtrack sequence
 583                                          * data--from beginning of table */
 584   OffsetTo<ClassDef>
 585                 inputClassDef;          /* Offset to glyph ClassDef
 586                                          * table containing input sequence
 587                                          * data--from beginning of table */
 588   OffsetTo<ClassDef>
 589                 lookaheadClassDef;      /* Offset to glyph ClassDef table
 590                                          * containing lookahead sequence
 591                                          * data--from beginning of table */
 592   OffsetArrayOf<ChainRuleSet>
 593                 ruleSet;                /* Array of ChainRuleSet tables
 594                                          * ordered by class */
 595 };
 596 ASSERT_SIZE (ChainContextFormat2, 12);
 597
 598 struct ChainContextFormat3 {
 599
 600   friend struct ChainContext;
 601
 602   private:
 603
 604   inline bool apply_coverage (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 605   }
 606
 607   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 608
 609     const OffsetArrayOf<Coverage> &input = * (const OffsetArrayOf<Coverage> *)
 610                                              ((const char *) &backtrack + backtrack.get_size ());
 611
 612     unsigned int index = (this+input[0]) (IN_CURGLYPH ());
 613     if (G_LIKELY (index == NOT_COVERED))
 614       return false;
 615
 616     const OffsetArrayOf<Coverage> &lookahead = * (const OffsetArrayOf<Coverage> *)
 617                                          ((const char *) &input + input.get_size ());
 618     const ArrayOf<LookupRecord> &lookup = * (const ArrayOf<LookupRecord> *)
 619                                             ((const char *) &lookahead + lookahead.get_size ());
 620     struct ChainContextLookupContext context = {
 621       {match_coverage, apply_func},
 622       {(char *) this, (char *) this, (char *) this}
 623     };
 624     return chain_context_lookup (LOOKUP_ARGS,
 625                                  backtrack.len,
 626                                  (USHORT *) backtrack.array,
 627                                  input.len,
 628                                  (USHORT *) input.array,
 629                                  lookahead.len,
 630                                  (USHORT *) lookahead.array,
 631                                  lookup.len,
 632                                  lookup.array,
 633                                  context);
 634     return false;
 635   }
 636
 637   private:
 638   USHORT        format;                 /* Format identifier--format = 3 */
 639   OffsetArrayOf<Coverage>
 640                 backtrack;              /* Array of coverage tables
 641                                          * in backtracking sequence, in  glyph
 642                                          * sequence order */
 643   OffsetArrayOf<Coverage>
 644                 inputX          ;       /* Array of coverage
 645                                          * tables in input sequence, in glyph
 646                                          * sequence order */
 647   OffsetArrayOf<Coverage>
 648                 lookaheadX;             /* Array of coverage tables
 649                                          * in lookahead sequence, in glyph
 650                                          * sequence order */
 651   ArrayOf<LookupRecord>
 652                 lookupX;                /* Array of LookupRecords--in
 653                                          * design order) */
 654 };
 655 ASSERT_SIZE (ChainContextFormat3, 10);
 656
 657 struct ChainContext {
 658
 659   protected:
 660   bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 661     switch (u.format) {
 662     case 1: return u.format1->apply (LOOKUP_ARGS, apply_func);
 663     case 2: return u.format2->apply (LOOKUP_ARGS, apply_func);
 664     case 3: return u.format3->apply (LOOKUP_ARGS, apply_func);
 665     default:return false;
 666     }
 667   }
 668
 669   private:
 670   union {
 671   USHORT                format; /* Format identifier */
 672   ChainContextFormat1   format1[];
 673   ChainContextFormat2   format2[];
 674   ChainContextFormat3   format3[];
 675   } u;
 676 };
 677 ASSERT_SIZE (ChainContext, 2);
 678
 679
 680 /*
 681  * GSUB/GPOS Common
 682  */
 683
 684 struct GSUBGPOS {
 685   static const hb_tag_t GSUBTag         = HB_TAG ('G','S','U','B');
 686   static const hb_tag_t GPOSTag         = HB_TAG ('G','P','O','S');
 687
 688   STATIC_DEFINE_GET_FOR_DATA (GSUBGPOS);
 689   /* XXX check version here? */
 690
 691   DEFINE_TAG_LIST_INTERFACE (Script,  script ); /* get_script_count (), get_script (i), get_script_tag (i) */
 692   DEFINE_TAG_LIST_INTERFACE (Feature, feature); /* get_feature_count(), get_feature(i), get_feature_tag(i) */
 693   DEFINE_LIST_INTERFACE     (Lookup,  lookup ); /* get_lookup_count (), get_lookup (i) */
 694
 695   // LONGTERMTODO bsearch
 696   DEFINE_TAG_FIND_INTERFACE (Script,  script ); /* find_script_index (), get_script_by_tag (tag) */
 697   DEFINE_TAG_FIND_INTERFACE (Feature, feature); /* find_feature_index(), get_feature_by_tag(tag) */
 698
 699   private:
 700   Fixed_Version version;        /* Version of the GSUB/GPOS table--initially set
 701                                  * to 0x00010000 */
 702   OffsetTo<ScriptList>
 703                 scriptList;     /* ScriptList table */
 704   OffsetTo<FeatureList>
 705                 featureList;    /* FeatureList table */
 706   OffsetTo<LookupList>
 707                 lookupList;     /* LookupList table */
 708 };
 709 ASSERT_SIZE (GSUBGPOS, 10);
 710
 711
 712 #endif /* HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H */