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
  83   /* XXX context_length should also be checked when skipping glyphs, right?
  84    * What does context_length really mean, anyway? */
  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 == buffer->in_length))
  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   unsigned int i, j;
 109
 110   for (i = 0, j = buffer->out_pos - 1; i < count; i++, j--) {
 111     while (!_hb_ot_layout_check_glyph_property (layout, OUT_ITEM (j), lookup_flag, &property)) {
 112       if (HB_UNLIKELY (j + 1 == count - i))
 113         return false;
 114       j--;
 115     }
 116
 117     if (HB_LIKELY (!match_func (OUT_GLYPH(j), backtrack[i], match_data)))
 118       return false;
 119   }
 120
 121   return true;
 122 }
 123
 124 static inline bool match_lookahead (LOOKUP_ARGS_DEF,
 125                                     unsigned int count,
 126                                     const USHORT lookahead[],
 127                                     match_func_t match_func,
 128                                     char *match_data,
 129                                     unsigned int offset)
 130 {
 131   unsigned int i, j;
 132
 133   for (i = 0, j = buffer->in_pos + offset; i < count; i++, j++) {
 134     while (!_hb_ot_layout_check_glyph_property (layout, OUT_ITEM (j), lookup_flag, &property)) {
 135       if (HB_UNLIKELY (j + count - i == buffer->in_length))
 136         return false;
 137       j++;
 138     }
 139
 140     if (HB_LIKELY (!match_func (IN_GLYPH(j), lookahead[i], match_data)))
 141       return false;
 142   }
 143
 144   return true;
 145 }
 146
 147
 148 struct LookupRecord {
 149
 150   USHORT        sequenceIndex;          /* Index into current glyph
 151                                          * sequence--first glyph = 0 */
 152   USHORT        lookupListIndex;        /* Lookup to apply to that
 153                                          * position--zero--based */
 154 };
 155 ASSERT_SIZE (LookupRecord, 4);
 156
 157 static inline bool apply_lookup (LOOKUP_ARGS_DEF,
 158                                  unsigned int count, /* Including the first glyph */
 159                                  unsigned int lookupCount,
 160                                  const LookupRecord lookupRecord[], /* Array of LookupRecords--in design order */
 161                                  apply_lookup_func_t apply_func)
 162 {
 163   unsigned int record_count = lookupCount;
 164   const LookupRecord *record = lookupRecord;
 165
 166   /* XXX We have to jump non-matching glyphs when applying too, right? */
 167   /* XXX We don't support lookupRecord arrays that are not increasing:
 168    *     Should be easy for in_place ones at least. */
 169   for (unsigned int i = 0; i < count;)
 170   {
 171     if (record_count && i == record->sequenceIndex)
 172     {
 173       unsigned int old_pos = buffer->in_pos;
 174
 175       /* Apply a lookup */
 176       bool done = apply_func (LOOKUP_ARGS, record->lookupListIndex);
 177
 178       record++;
 179       record_count--;
 180       i += buffer->in_pos - old_pos;
 181
 182       if (!done)
 183         goto not_applied;
 184     }
 185     else
 186     {
 187     not_applied:
 188       /* No lookup applied for this index */
 189       _hb_buffer_next_glyph (buffer);
 190       i++;
 191     }
 192   }
 193
 194   return true;
 195 }
 196
 197
 198 /* Contextual lookups */
 199
 200 struct ContextLookupContext {
 201   ContextFuncs funcs;
 202   char *match_data;
 203 };
 204
 205 static inline bool context_lookup (LOOKUP_ARGS_DEF,
 206                                    unsigned int inputCount, /* Including the first glyph (not matched) */
 207                                    const USHORT input[], /* Array of input values--start with second glyph */
 208                                    unsigned int lookupCount,
 209                                    const LookupRecord lookupRecord[],
 210                                    ContextLookupContext &context)
 211 {
 212   /* First guess */
 213   if (HB_UNLIKELY (buffer->in_pos + inputCount > buffer->in_length ||
 214                    context_length < inputCount))
 215     return false;
 216
 217   return match_input (LOOKUP_ARGS,
 218                       inputCount, input,
 219                       context.funcs.match, context.match_data,
 220                       &context_length) &&
 221          apply_lookup (LOOKUP_ARGS,
 222                        inputCount,
 223                        lookupCount, lookupRecord,
 224                        context.funcs.apply);
 225 }
 226
 227 struct Rule {
 228
 229   friend struct RuleSet;
 230
 231   private:
 232   inline bool apply (LOOKUP_ARGS_DEF, ContextLookupContext &context) const {
 233     const LookupRecord *lookupRecord = (const LookupRecord *)
 234                                        ((const char *) input +
 235                                         sizeof (input[0]) * (inputCount ? inputCount - 1 : 0));
 236     return context_lookup (LOOKUP_ARGS,
 237                            inputCount,
 238                            input,
 239                            lookupCount,
 240                            lookupRecord,
 241                            context);
 242   }
 243
 244   private:
 245   USHORT        inputCount;             /* Total number of glyphs in input
 246                                          * glyph sequence--includes the  first
 247                                          * glyph */
 248   USHORT        lookupCount;            /* Number of LookupRecords */
 249   USHORT        input[];                /* Array of match inputs--start with
 250                                          * second glyph */
 251   LookupRecord  lookupRecordX[];        /* Array of LookupRecords--in
 252                                          * design order */
 253 };
 254 ASSERT_SIZE (Rule, 4);
 255
 256 struct RuleSet {
 257
 258   inline bool apply (LOOKUP_ARGS_DEF, ContextLookupContext &context) const {
 259
 260     unsigned int num_rules = rule.len;
 261     for (unsigned int i = 0; i < num_rules; i++) {
 262       if ((this+rule[i]).apply (LOOKUP_ARGS, context))
 263         return true;
 264     }
 265
 266     return false;
 267   }
 268
 269   private:
 270   OffsetArrayOf<Rule>
 271                 rule;                   /* Array of Rule tables
 272                                          * ordered by preference */
 273 };
 274
 275
 276 struct ContextFormat1 {
 277
 278   friend struct Context;
 279
 280   private:
 281   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 282
 283     unsigned int index = (this+coverage) (IN_CURGLYPH ());
 284     if (G_LIKELY (index == NOT_COVERED))
 285       return false;
 286
 287     const RuleSet &rule_set = this+ruleSet[index];
 288     struct ContextLookupContext context = {
 289       {match_glyph, apply_func},
 290       NULL
 291     };
 292     return rule_set.apply (LOOKUP_ARGS, context);
 293   }
 294
 295   private:
 296   USHORT        format;                 /* Format identifier--format = 1 */
 297   OffsetTo<Coverage>
 298                 coverage;               /* Offset to Coverage table--from
 299                                          * beginning of table */
 300   OffsetArrayOf<RuleSet>
 301                 ruleSet;                /* Array of RuleSet tables
 302                                          * ordered by Coverage Index */
 303 };
 304 ASSERT_SIZE (ContextFormat1, 6);
 305
 306
 307 struct ContextFormat2 {
 308
 309   friend struct Context;
 310
 311   private:
 312   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 313
 314     unsigned int index = (this+coverage) (IN_CURGLYPH ());
 315     if (G_LIKELY (index == NOT_COVERED))
 316       return false;
 317
 318     const ClassDef &class_def = this+classDef;
 319     index = class_def (IN_CURGLYPH ());
 320     const RuleSet &rule_set = this+ruleSet[index];
 321     /* LONGTERMTODO: Old code fetches glyph classes at most once and caches
 322      * them across subrule lookups.  Not sure it's worth it.
 323      */
 324     struct ContextLookupContext context = {
 325      {match_class, apply_func},
 326       (char *) &class_def
 327     };
 328     return rule_set.apply (LOOKUP_ARGS, context);
 329   }
 330
 331   private:
 332   USHORT        format;                 /* Format identifier--format = 2 */
 333   OffsetTo<Coverage>
 334                 coverage;               /* Offset to Coverage table--from
 335                                          * beginning of table */
 336   OffsetTo<ClassDef>
 337                 classDef;               /* Offset to glyph ClassDef table--from
 338                                          * beginning of table */
 339   OffsetArrayOf<RuleSet>
 340                 ruleSet;                /* Array of RuleSet tables
 341                                          * ordered by class */
 342 };
 343 ASSERT_SIZE (ContextFormat2, 8);
 344
 345
 346 struct ContextFormat3 {
 347
 348   friend struct Context;
 349
 350   private:
 351   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 352
 353     unsigned int index = (this+coverage[0]) (IN_CURGLYPH ());
 354     if (G_LIKELY (index == NOT_COVERED))
 355       return false;
 356
 357     const LookupRecord *lookupRecord = (const LookupRecord *)
 358                                        ((const char *) coverage +
 359                                         sizeof (coverage[0]) * glyphCount);
 360     struct ContextLookupContext context = {
 361       {match_coverage, apply_func},
 362       (char *) this
 363     };
 364     return context_lookup (LOOKUP_ARGS,
 365                            glyphCount,
 366                            (const USHORT *) (coverage + 1),
 367                            lookupCount,
 368                            lookupRecord,
 369                            context);
 370   }
 371
 372   private:
 373   USHORT        format;                 /* Format identifier--format = 3 */
 374   USHORT        glyphCount;             /* Number of glyphs in the input glyph
 375                                          * sequence */
 376   USHORT        lookupCount;            /* Number of LookupRecords */
 377   OffsetTo<Coverage>
 378                 coverage[];             /* Array of offsets to Coverage
 379                                          * table in glyph sequence order */
 380   LookupRecord  lookupRecordX[];        /* Array of LookupRecords--in
 381                                          * design order */
 382 };
 383 ASSERT_SIZE (ContextFormat3, 6);
 384
 385 struct Context {
 386
 387   protected:
 388   bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 389     switch (u.format) {
 390     case 1: return u.format1->apply (LOOKUP_ARGS, apply_func);
 391     case 2: return u.format2->apply (LOOKUP_ARGS, apply_func);
 392     case 3: return u.format3->apply (LOOKUP_ARGS, apply_func);
 393     default:return false;
 394     }
 395   }
 396
 397   private:
 398   union {
 399   USHORT                format;         /* Format identifier */
 400   ContextFormat1        format1[];
 401   ContextFormat2        format2[];
 402   ContextFormat3        format3[];
 403   } u;
 404 };
 405 ASSERT_SIZE (Context, 2);
 406
 407
 408 /* Chaining Contextual lookups */
 409
 410 struct ChainContextLookupContext {
 411   ContextFuncs funcs;
 412   char *match_data[3];
 413 };
 414
 415 static inline bool chain_context_lookup (LOOKUP_ARGS_DEF,
 416                                          unsigned int backtrackCount,
 417                                          const USHORT backtrack[],
 418                                          unsigned int inputCount, /* Including the first glyph (not matched) */
 419                                          const USHORT input[], /* Array of input values--start with second glyph */
 420                                          unsigned int lookaheadCount,
 421                                          const USHORT lookahead[],
 422                                          unsigned int lookupCount,
 423                                          const LookupRecord lookupRecord[],
 424                                          ChainContextLookupContext &context)
 425 {
 426   /* First guess */
 427   if (HB_UNLIKELY (buffer->out_pos < backtrackCount ||
 428                    buffer->in_pos + inputCount + lookaheadCount > buffer->in_length))
 429     return false;
 430
 431   unsigned int offset;
 432   return match_backtrack (LOOKUP_ARGS,
 433                           backtrackCount, backtrack,
 434                           context.funcs.match, context.match_data[0]) &&
 435          match_input (LOOKUP_ARGS,
 436                       inputCount, input,
 437                       context.funcs.match, context.match_data[1],
 438                       &offset) &&
 439          (context_length -= offset, true) &&
 440          match_lookahead (LOOKUP_ARGS,
 441                           lookaheadCount, lookahead,
 442                           context.funcs.match, context.match_data[2],
 443                           offset) &&
 444          (context_length = offset, true) &&
 445          apply_lookup (LOOKUP_ARGS,
 446                        inputCount,
 447                        lookupCount, lookupRecord,
 448                        context.funcs.apply);
 449 }
 450
 451 struct ChainRule {
 452
 453   friend struct ChainRuleSet;
 454
 455   private:
 456   inline bool apply (LOOKUP_ARGS_DEF, ChainContextLookupContext &context) const {
 457     const HeadlessArrayOf<USHORT> &input = * (const HeadlessArrayOf<USHORT> *)
 458                                              ((const char *) &backtrack + backtrack.get_size ());
 459     const ArrayOf<USHORT> &lookahead = * (const ArrayOf<USHORT> *)
 460                                          ((const char *) &input + input.get_size ());
 461     const ArrayOf<LookupRecord> &lookup = * (const ArrayOf<LookupRecord> *)
 462                                             ((const char *) &lookahead + lookahead.get_size ());
 463     return chain_context_lookup (LOOKUP_ARGS,
 464                                  backtrack.len,
 465                                  backtrack.array,
 466                                  input.len,
 467                                  input.array + 1,
 468                                  lookahead.len,
 469                                  lookahead.array,
 470                                  lookup.len,
 471                                  lookup.array,
 472                                  context);
 473     return false;
 474   }
 475
 476
 477   private:
 478   ArrayOf<USHORT>
 479                 backtrack;              /* Array of backtracking values
 480                                          * (to be matched before the input
 481                                          * sequence) */
 482   HeadlessArrayOf<USHORT>
 483                 inputX;                 /* Array of input values (start with
 484                                          * second glyph) */
 485   ArrayOf<USHORT>
 486                 lookaheadX;             /* Array of lookahead values's (to be
 487                                          * matched after the input sequence) */
 488   ArrayOf<LookupRecord>
 489                 lookupX;                /* Array of LookupRecords--in
 490                                          * design order) */
 491 };
 492 ASSERT_SIZE (ChainRule, 8);
 493
 494 struct ChainRuleSet {
 495
 496   inline bool apply (LOOKUP_ARGS_DEF, ChainContextLookupContext &context) const {
 497
 498     unsigned int num_rules = rule.len;
 499     for (unsigned int i = 0; i < num_rules; i++) {
 500       if ((this+rule[i]).apply (LOOKUP_ARGS, context))
 501         return true;
 502     }
 503
 504     return false;
 505   }
 506
 507   private:
 508   OffsetArrayOf<ChainRule>
 509                 rule;                   /* Array of ChainRule tables
 510                                          * ordered by preference */
 511 };
 512 ASSERT_SIZE (ChainRuleSet, 2);
 513
 514 struct ChainContextFormat1 {
 515
 516   friend struct ChainContext;
 517
 518   private:
 519   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 520
 521     unsigned int index = (this+coverage) (IN_CURGLYPH ());
 522     if (G_LIKELY (index == NOT_COVERED))
 523       return false;
 524
 525     const ChainRuleSet &rule_set = this+ruleSet[index];
 526     struct ChainContextLookupContext context = {
 527       {match_glyph, apply_func},
 528       {NULL, NULL, NULL}
 529     };
 530     return rule_set.apply (LOOKUP_ARGS, context);
 531   }
 532   private:
 533   USHORT        format;                 /* Format identifier--format = 1 */
 534   OffsetTo<Coverage>
 535                 coverage;               /* Offset to Coverage table--from
 536                                          * beginning of table */
 537   OffsetArrayOf<ChainRuleSet>
 538                 ruleSet;                /* Array of ChainRuleSet tables
 539                                          * ordered by Coverage Index */
 540 };
 541 ASSERT_SIZE (ChainContextFormat1, 6);
 542
 543 struct ChainContextFormat2 {
 544
 545   friend struct ChainContext;
 546
 547   private:
 548   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 549
 550     unsigned int index = (this+coverage) (IN_CURGLYPH ());
 551     if (G_LIKELY (index == NOT_COVERED))
 552       return false;
 553
 554     const ClassDef &backtrack_class_def = this+backtrackClassDef;
 555     const ClassDef &input_class_def = this+inputClassDef;
 556     const ClassDef &lookahead_class_def = this+lookaheadClassDef;
 557
 558     index = input_class_def (IN_CURGLYPH ());
 559     const ChainRuleSet &rule_set = this+ruleSet[index];
 560     /* LONGTERMTODO: Old code fetches glyph classes at most once and caches
 561      * them across subrule lookups.  Not sure it's worth it.
 562      */
 563     struct ChainContextLookupContext context = {
 564      {match_class, apply_func},
 565      {(char *) &backtrack_class_def,
 566       (char *) &input_class_def,
 567       (char *) &lookahead_class_def}
 568     };
 569     return rule_set.apply (LOOKUP_ARGS, context);
 570   }
 571
 572   private:
 573   USHORT        format;                 /* Format identifier--format = 2 */
 574   OffsetTo<Coverage>
 575                 coverage;               /* Offset to Coverage table--from
 576                                          * beginning of table */
 577   OffsetTo<ClassDef>
 578                 backtrackClassDef;      /* Offset to glyph ClassDef table
 579                                          * containing backtrack sequence
 580                                          * data--from beginning of table */
 581   OffsetTo<ClassDef>
 582                 inputClassDef;          /* Offset to glyph ClassDef
 583                                          * table containing input sequence
 584                                          * data--from beginning of table */
 585   OffsetTo<ClassDef>
 586                 lookaheadClassDef;      /* Offset to glyph ClassDef table
 587                                          * containing lookahead sequence
 588                                          * data--from beginning of table */
 589   OffsetArrayOf<ChainRuleSet>
 590                 ruleSet;                /* Array of ChainRuleSet tables
 591                                          * ordered by class */
 592 };
 593 ASSERT_SIZE (ChainContextFormat2, 12);
 594
 595 struct ChainContextFormat3 {
 596
 597   friend struct ChainContext;
 598
 599   private:
 600
 601   inline bool apply_coverage (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 602   }
 603
 604   inline bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 605
 606     const OffsetArrayOf<Coverage> &input = * (const OffsetArrayOf<Coverage> *)
 607                                              ((const char *) &backtrack + backtrack.get_size ());
 608
 609     unsigned int index = (this+input[0]) (IN_CURGLYPH ());
 610     if (G_LIKELY (index == NOT_COVERED))
 611       return false;
 612
 613     const OffsetArrayOf<Coverage> &lookahead = * (const OffsetArrayOf<Coverage> *)
 614                                          ((const char *) &input + input.get_size ());
 615     const ArrayOf<LookupRecord> &lookup = * (const ArrayOf<LookupRecord> *)
 616                                             ((const char *) &lookahead + lookahead.get_size ());
 617     struct ChainContextLookupContext context = {
 618       {match_coverage, apply_func},
 619       {(char *) this, (char *) this, (char *) this}
 620     };
 621     return chain_context_lookup (LOOKUP_ARGS,
 622                                  backtrack.len,
 623                                  (USHORT *) backtrack.array,
 624                                  input.len,
 625                                  (USHORT *) input.array,
 626                                  lookahead.len,
 627                                  (USHORT *) lookahead.array,
 628                                  lookup.len,
 629                                  lookup.array,
 630                                  context);
 631     return false;
 632   }
 633
 634   private:
 635   USHORT        format;                 /* Format identifier--format = 3 */
 636   OffsetArrayOf<Coverage>
 637                 backtrack;              /* Array of coverage tables
 638                                          * in backtracking sequence, in  glyph
 639                                          * sequence order */
 640   OffsetArrayOf<Coverage>
 641                 inputX          ;       /* Array of coverage
 642                                          * tables in input sequence, in glyph
 643                                          * sequence order */
 644   OffsetArrayOf<Coverage>
 645                 lookaheadX;             /* Array of coverage tables
 646                                          * in lookahead sequence, in glyph
 647                                          * sequence order */
 648   ArrayOf<LookupRecord>
 649                 lookupX;                /* Array of LookupRecords--in
 650                                          * design order) */
 651 };
 652 ASSERT_SIZE (ChainContextFormat3, 10);
 653
 654 struct ChainContext {
 655
 656   protected:
 657   bool apply (LOOKUP_ARGS_DEF, apply_lookup_func_t apply_func) const {
 658     switch (u.format) {
 659     case 1: return u.format1->apply (LOOKUP_ARGS, apply_func);
 660     case 2: return u.format2->apply (LOOKUP_ARGS, apply_func);
 661     case 3: return u.format3->apply (LOOKUP_ARGS, apply_func);
 662     default:return false;
 663     }
 664   }
 665
 666   private:
 667   union {
 668   USHORT                format; /* Format identifier */
 669   ChainContextFormat1   format1[];
 670   ChainContextFormat2   format2[];
 671   ChainContextFormat3   format3[];
 672   } u;
 673 };
 674 ASSERT_SIZE (ChainContext, 2);
 675
 676
 677 /*
 678  * GSUB/GPOS Common
 679  */
 680
 681 struct GSUBGPOS {
 682   static const hb_tag_t GSUBTag         = HB_TAG ('G','S','U','B');
 683   static const hb_tag_t GPOSTag         = HB_TAG ('G','P','O','S');
 684
 685   STATIC_DEFINE_GET_FOR_DATA (GSUBGPOS);
 686   /* XXX check version here? */
 687
 688   DEFINE_TAG_LIST_INTERFACE (Script,  script ); /* get_script_count (), get_script (i), get_script_tag (i) */
 689   DEFINE_TAG_LIST_INTERFACE (Feature, feature); /* get_feature_count(), get_feature(i), get_feature_tag(i) */
 690   DEFINE_LIST_INTERFACE     (Lookup,  lookup ); /* get_lookup_count (), get_lookup (i) */
 691
 692   // LONGTERMTODO bsearch
 693   DEFINE_TAG_FIND_INTERFACE (Script,  script ); /* find_script_index (), get_script_by_tag (tag) */
 694   DEFINE_TAG_FIND_INTERFACE (Feature, feature); /* find_feature_index(), get_feature_by_tag(tag) */
 695
 696   private:
 697   Fixed_Version version;        /* Version of the GSUB/GPOS table--initially set
 698                                  * to 0x00010000 */
 699   OffsetTo<ScriptList>
 700                 scriptList;     /* ScriptList table */
 701   OffsetTo<FeatureList>
 702                 featureList;    /* FeatureList table */
 703   OffsetTo<LookupList>
 704                 lookupList;     /* LookupList table */
 705 };
 706 ASSERT_SIZE (GSUBGPOS, 10);
 707
 708
 709 #endif /* HB_OT_LAYOUT_GSUBGPOS_PRIVATE_H */