lib/tashaper.c

   1 /* tashaper.c */
   2
   3 /*
   4  * Copyright (C) 2014-2018 by Werner Lemberg.
   5  *
   6  * This file is part of the ttfautohint library, and may only be used,
   7  * modified, and distributed under the terms given in `COPYING'.  By
   8  * continuing to use, modify, or distribute this file you indicate that you
   9  * have read `COPYING' and understand and accept it fully.
  10  *
  11  * The file `COPYING' mentioned in the previous paragraph is distributed
  12  * with the ttfautohint library.
  13  */
  14
  15
  16 /* originally file `hbshim.c' (2014-Jan-11) from FreeType */
  17
  18 /* heavily modified 2014 by Werner Lemberg <wl@gnu.org> */
  19
  20 #include "tashaper.h"
  21
  22
  23 /*
  24  * We use `sets' (in the HarfBuzz sense, which comes quite near to the
  25  * usual mathematical meaning) to manage both lookups and glyph indices.
  26  *
  27  * 1. For each coverage, collect lookup IDs in a set.  Note that an
  28  *    auto-hinter `coverage' is represented by one `feature', and a
  29  *    feature consists of an arbitrary number of (font specific) `lookup's
  30  *    that actually do the mapping job.  Please check the OpenType
  31  *    specification for more details on features and lookups.
  32  *
  33  * 2. Create glyph ID sets from the corresponding lookup sets.
  34  *
  35  * 3. The glyph set corresponding to TA_COVERAGE_DEFAULT is computed
  36  *    with all lookups specific to the OpenType script activated.  It
  37  *    relies on the order of ta_style_classes entries so that
  38  *    special coverages (like `oldstyle figures') don't get overwritten.
  39  */
  40
  41
  42 /* load coverage tags */
  43 #undef COVERAGE
  44 #define COVERAGE(name, NAME, description, \
  45                  tag, tag1, tag2, tag3, tag4) \
  46           static const hb_tag_t name ## _coverage[] = \
  47           { \
  48             HB_TAG(tag1, tag2, tag3, tag4), \
  49             HB_TAG_NONE \
  50           };
  51
  52 #include "ttfautohint-coverages.h"
  53
  54
  55 /* define mapping between coverage tags and TA_Coverage */
  56 #undef COVERAGE
  57 #define COVERAGE(name, NAME, description, \
  58                  tag, tag1, tag2, tag3, tag4) \
  59           name ## _coverage,
  60
  61 static const hb_tag_t* coverages[] =
  62 {
  63 #include "ttfautohint-coverages.h"
  64
  65   NULL /* TA_COVERAGE_DEFAULT */
  66 };
  67
  68
  69 /* load HarfBuzz script tags */
  70 #undef SCRIPT
  71 #define SCRIPT(s, S, d, h, H, ss) h,
  72
  73 static const hb_script_t scripts[] =
  74 {
  75 #include "ttfautohint-scripts.h"
  76 };
  77
  78
  79 FT_Error
  80 ta_shaper_get_coverage(TA_FaceGlobals globals,
  81                        TA_StyleClass style_class,
  82                        FT_UShort* gstyles,
  83                        FT_UInt* sample_glyph,
  84                        FT_Bool default_script)
  85 {
  86   hb_face_t* face;
  87
  88   hb_set_t* gsub_lookups; /* GSUB lookups for a given script */
  89   hb_set_t* gsub_glyphs; /* glyphs covered by GSUB lookups */
  90   hb_set_t* gpos_lookups; /* GPOS lookups for a given script */
  91   hb_set_t* gpos_glyphs; /* glyphs covered by GPOS lookups */
  92
  93   hb_script_t script;
  94   const hb_tag_t* coverage_tags;
  95   hb_tag_t script_tags[] = { HB_TAG_NONE,
  96                              HB_TAG_NONE,
  97                              HB_TAG_NONE,
  98                              HB_TAG_NONE };
  99
 100   hb_codepoint_t idx;
 101 #ifdef TA_DEBUG
 102   int count;
 103 #endif
 104
 105
 106   if (!globals || !style_class || !gstyles)
 107     return FT_Err_Invalid_Argument;
 108
 109   face = hb_font_get_face(globals->hb_font);
 110
 111   gsub_lookups = hb_set_create();
 112   gsub_glyphs = hb_set_create();
 113   gpos_lookups = hb_set_create();
 114   gpos_glyphs = hb_set_create();
 115
 116   coverage_tags = coverages[style_class->coverage];
 117   script = scripts[style_class->script];
 118
 119   /* convert a HarfBuzz script tag into the corresponding OpenType */
 120   /* tag or tags -- some Indic scripts like Devanagari have an old */
 121   /* and a new set of features */
 122   hb_ot_tags_from_script(script,
 123                          &script_tags[0],
 124                          &script_tags[1]);
 125
 126   /* `hb_ot_tags_from_script' usually returns HB_OT_TAG_DEFAULT_SCRIPT */
 127   /* as the second tag; we change that to HB_TAG_NONE except for the */
 128   /* default script */
 129   if (default_script)
 130   {
 131     if (script_tags[0] == HB_TAG_NONE)
 132       script_tags[0] = HB_OT_TAG_DEFAULT_SCRIPT;
 133     else
 134     {
 135       if (script_tags[1] == HB_TAG_NONE)
 136         script_tags[1] = HB_OT_TAG_DEFAULT_SCRIPT;
 137       else if (script_tags[1] != HB_OT_TAG_DEFAULT_SCRIPT)
 138         script_tags[2] = HB_OT_TAG_DEFAULT_SCRIPT;
 139     }
 140   }
 141   else
 142   {
 143     /* we use non-standard tags like `khms' for special purposes; */
 144     /* HarfBuzz maps them to `DFLT', which we don't want to handle here */
 145     if (script_tags[0] == HB_OT_TAG_DEFAULT_SCRIPT)
 146       goto Exit;
 147
 148     if (script_tags[1] == HB_OT_TAG_DEFAULT_SCRIPT)
 149       script_tags[1] = HB_TAG_NONE;
 150   }
 151
 152   hb_ot_layout_collect_lookups(face,
 153                                HB_OT_TAG_GSUB,
 154                                script_tags,
 155                                NULL,
 156                                coverage_tags,
 157                                gsub_lookups);
 158
 159   if (hb_set_is_empty(gsub_lookups))
 160     goto Exit; /* nothing to do */
 161
 162   hb_ot_layout_collect_lookups(face,
 163                                HB_OT_TAG_GPOS,
 164                                script_tags,
 165                                NULL,
 166                                coverage_tags,
 167                                gpos_lookups);
 168
 169   TA_LOG_GLOBAL(("GSUB lookups (style `%s'):\n"
 170                  " ",
 171                  ta_style_names[style_class->style]));
 172
 173 #ifdef TA_DEBUG
 174   count = 0;
 175 #endif
 176
 177   for (idx = HB_SET_VALUE_INVALID; hb_set_next(gsub_lookups, &idx);)
 178   {
 179 #ifdef TA_DEBUG
 180     TA_LOG_GLOBAL((" %d", idx));
 181     count++;
 182 #endif
 183
 184     /* get output coverage of GSUB feature */
 185     hb_ot_layout_lookup_collect_glyphs(face,
 186                                        HB_OT_TAG_GSUB,
 187                                        idx,
 188                                        NULL,
 189                                        NULL,
 190                                        NULL,
 191                                        gsub_glyphs);
 192   }
 193
 194 #ifdef TA_DEBUG
 195   if (!count)
 196     TA_LOG_GLOBAL((" (none)"));
 197   TA_LOG_GLOBAL(("\n\n"));
 198 #endif
 199
 200   TA_LOG_GLOBAL(("GPOS lookups (style `%s'):\n"
 201                  " ",
 202                  ta_style_names[style_class->style]));
 203
 204 #ifdef TA_DEBUG
 205   count = 0;
 206 #endif
 207
 208   for (idx = HB_SET_VALUE_INVALID; hb_set_next(gpos_lookups, &idx);)
 209   {
 210 #ifdef TA_DEBUG
 211     TA_LOG_GLOBAL((" %d", idx));
 212     count++;
 213 #endif
 214
 215     /* get input coverage of GPOS feature */
 216     hb_ot_layout_lookup_collect_glyphs(face,
 217                                        HB_OT_TAG_GPOS,
 218                                        idx,
 219                                        NULL,
 220                                        gpos_glyphs,
 221                                        NULL,
 222                                        NULL);
 223   }
 224
 225 #ifdef TA_DEBUG
 226   if (!count)
 227     TA_LOG_GLOBAL((" (none)"));
 228   TA_LOG_GLOBAL(("\n\n"));
 229 #endif
 230
 231   /*
 232    * we now check whether we can construct blue zones, using glyphs
 233    * covered by the feature only -- in case there is not a single zone
 234    * (this is, not a single character is covered), we skip this coverage
 235    */
 236   if (style_class->coverage != TA_COVERAGE_DEFAULT)
 237   {
 238     TA_Blue_Stringset bss = style_class->blue_stringset;
 239     const TA_Blue_StringRec* bs = &ta_blue_stringsets[bss];
 240
 241     FT_Bool found = 0;
 242
 243
 244     for (; bs->string != TA_BLUE_STRING_MAX; bs++)
 245     {
 246       const char* p = &ta_blue_strings[bs->string];
 247
 248
 249       while (*p)
 250       {
 251         hb_codepoint_t ch;
 252
 253
 254         GET_UTF8_CHAR(ch, p);
 255
 256         for (idx = HB_SET_VALUE_INVALID; hb_set_next(gsub_lookups, &idx);)
 257         {
 258           hb_codepoint_t gidx = FT_Get_Char_Index(globals->face, ch);
 259
 260
 261           if (hb_ot_layout_lookup_would_substitute(face, idx,
 262                                                    &gidx, 1, 1))
 263           {
 264             found = 1;
 265             break;
 266           }
 267         }
 268       }
 269     }
 270
 271     if (!found)
 272     {
 273       TA_LOG_GLOBAL(("  no blue characters found; style skipped\n"));
 274       goto Exit;
 275     }
 276   }
 277
 278   /*
 279    * Various OpenType features might use the same glyphs at different
 280    * vertical positions; for example, superscript and subscript glyphs
 281    * could be the same.  However, the auto-hinter is completely
 282    * agnostic of OpenType features after the feature analysis has been
 283    * completed: The engine then simply receives a glyph index and returns a
 284    * hinted and usually rendered glyph.
 285    *
 286    * Consider the superscript feature of font `pala.ttf': Some of the
 287    * glyphs are `real', this is, they have a zero vertical offset, but
 288    * most of them are small caps glyphs shifted up to the superscript
 289    * position (this is, the `sups' feature is present in both the GSUB and
 290    * GPOS tables).  The code for blue zones computation actually uses a
 291    * feature's y offset so that the `real' glyphs get correct hints.  But
 292    * later on it is impossible to decide whether a glyph index belongs to,
 293    * say, the small caps or superscript feature.
 294    *
 295    * For this reason, we don't assign a style to a glyph if the current
 296    * feature covers the glyph in both the GSUB and the GPOS tables.  This
 297    * is quite a broad condition, assuming that
 298    *
 299    *   (a) glyphs that get used in multiple features are present in a
 300    *       feature without vertical shift,
 301    *
 302    * and
 303    *
 304    *   (b) a feature's GPOS data really moves the glyph vertically.
 305    *
 306    * Not fulfilling condition (a) makes a font larger; it would also
 307    * reduce the number of glyphs that could be addressed directly without
 308    * using OpenType features, so this assumption is rather strong.
 309    *
 310    * Condition (b) is much weaker, and there might be glyphs which get
 311    * missed.  However, the OpenType features we are going to handle are
 312    * primarily located in GSUB, and HarfBuzz doesn't provide an API to
 313    * directly get the necessary information from the GPOS table.  A
 314    * possible solution might be to directly parse the GPOS table to find
 315    * out whether a glyph gets shifted vertically, but this is something I
 316    * would like to avoid if not really necessary.
 317    *
 318    * Note that we don't follow this logic for the default coverage.
 319    * Complex scripts like Devanagari have mandatory GPOS features to
 320    * position many glyph elements, using mark-to-base or mark-to-ligature
 321    * tables; the number of glyphs missed due to condition (b) would be far
 322    * too large.
 323    */
 324   if (style_class->coverage != TA_COVERAGE_DEFAULT)
 325     hb_set_subtract(gsub_glyphs, gpos_glyphs);
 326
 327 #ifdef TA_DEBUG
 328   TA_LOG_GLOBAL(("  glyphs without GPOS data (`*' means already assigned)"));
 329   count = 0;
 330 #endif
 331
 332   for (idx = HB_SET_VALUE_INVALID; hb_set_next(gsub_glyphs, &idx);)
 333   {
 334 #ifdef TA_DEBUG
 335     if (!(count % 10))
 336       TA_LOG_GLOBAL(("\n"
 337                      "   "));
 338
 339     TA_LOG_GLOBAL((" %d", idx));
 340     count++;
 341 #endif
 342
 343     /* glyph indices returned by `hb_ot_layout_lookup_collect_glyphs' */
 344     /* can be arbitrary: some fonts use fake indices for processing */
 345     /* internal to GSUB or GPOS, which is fully valid */
 346     if (idx >= (hb_codepoint_t)globals->glyph_count)
 347       continue;
 348
 349     if (gstyles[idx] == TA_STYLE_UNASSIGNED)
 350     {
 351       gstyles[idx] = (FT_UShort)style_class->style;
 352       if (!*sample_glyph)
 353         *sample_glyph = idx;
 354     }
 355 #ifdef TA_DEBUG
 356     else
 357       TA_LOG_GLOBAL(("*"));
 358 #endif
 359   }
 360
 361 #ifdef TA_DEBUG
 362     if (!count)
 363       TA_LOG_GLOBAL(("\n"
 364                      "    (none)"));
 365     TA_LOG_GLOBAL(("\n\n"));
 366 #endif
 367
 368 Exit:
 369   hb_set_destroy(gsub_lookups);
 370   hb_set_destroy(gsub_glyphs);
 371   hb_set_destroy(gpos_lookups);
 372   hb_set_destroy(gpos_glyphs);
 373
 374   return FT_Err_Ok;
 375 }
 376
 377
 378 /* construct HarfBuzz features */
 379 #undef COVERAGE
 380 #define COVERAGE(name, NAME, description, \
 381                  tag, tag1, tag2, tag3, tag4) \
 382           static const hb_feature_t name ## _feature[] = \
 383           { \
 384             { \
 385               HB_TAG(tag1, tag2, tag3, tag4), \
 386               1, 0, (unsigned int)-1 \
 387             } \
 388           };
 389
 390 #include "ttfautohint-coverages.h"
 391
 392
 393 /* define mapping between HarfBuzz features and TA_Coverage */
 394 #undef COVERAGE
 395 #define COVERAGE(name, NAME, description, \
 396                  tag, tag1, tag2, tag3, tag4) \
 397           name ## _feature,
 398
 399 static const hb_feature_t* features[] =
 400 {
 401 #include "ttfautohint-coverages.h"
 402
 403   NULL /* TA_COVERAGE_DEFAULT */
 404 };
 405
 406
 407 void*
 408 ta_shaper_buf_create(FT_Face face)
 409 {
 410   FT_UNUSED(face);
 411
 412   return (void*)hb_buffer_create();
 413 }
 414
 415
 416 void
 417 ta_shaper_buf_destroy(FT_Face face,
 418                       void* buf)
 419 {
 420   FT_UNUSED(face);
 421
 422   hb_buffer_destroy((hb_buffer_t*)buf);
 423 }
 424
 425
 426 const char*
 427 ta_shaper_get_cluster(const char* p,
 428                       TA_StyleMetrics metrics,
 429                       void* buf_,
 430                       unsigned int* count)
 431 {
 432   TA_StyleClass style_class;
 433   const hb_feature_t* feature;
 434   FT_Int upem;
 435   const char* q;
 436   int len;
 437
 438   hb_buffer_t* buf = (hb_buffer_t*)buf_;
 439   hb_font_t* font;
 440   hb_codepoint_t dummy;
 441
 442
 443   upem = (FT_Int)metrics->globals->face->units_per_EM;
 444   style_class = metrics->style_class;
 445   feature = features[style_class->coverage];
 446
 447   font = metrics->globals->hb_font;
 448
 449   /* we shape at a size of units per EM; this means font units */
 450   hb_font_set_scale(font, upem, upem);
 451
 452   while (*p == ' ')
 453     p++;
 454
 455   /* count bytes up to next space (or end of buffer) */
 456   q = p;
 457   while (!(*q == ' ' || *q == '\0'))
 458     GET_UTF8_CHAR(dummy, q);
 459   len = (int)(q - p);
 460
 461   /* feed character(s) to the HarfBuzz buffer */
 462   hb_buffer_clear_contents(buf);
 463   hb_buffer_add_utf8(buf, p, len, 0, len);
 464
 465   /* we let HarfBuzz guess the script and writing direction */
 466   hb_buffer_guess_segment_properties(buf);
 467
 468   /* shape buffer, which means conversion from character codes to */
 469   /* glyph indices, possibly applying a feature                   */
 470   hb_shape(font, buf, feature, feature ? 1 : 0);
 471
 472   if (feature)
 473   {
 474     hb_buffer_t* hb_buf = metrics->globals->hb_buf;
 475
 476     unsigned int gcount;
 477     hb_glyph_info_t* ginfo;
 478
 479     unsigned int hb_gcount;
 480     hb_glyph_info_t* hb_ginfo;
 481
 482
 483     /* we have to check whether applying a feature does actually change */
 484     /* glyph indices; otherwise the affected glyph or glyphs aren't */
 485     /* available at all in the feature */
 486
 487     hb_buffer_clear_contents(hb_buf);
 488     hb_buffer_add_utf8(hb_buf, p, len, 0, len);
 489     hb_buffer_guess_segment_properties(hb_buf);
 490     hb_shape(font, hb_buf, NULL, 0);
 491
 492     ginfo = hb_buffer_get_glyph_infos(buf, &gcount);
 493     hb_ginfo = hb_buffer_get_glyph_infos(hb_buf, &hb_gcount);
 494
 495     if (gcount == hb_gcount)
 496     {
 497       unsigned int i;
 498
 499
 500       for (i = 0; i < gcount; i++)
 501         if (ginfo[i].codepoint != hb_ginfo[i].codepoint)
 502           break;
 503
 504       if (i == gcount)
 505       {
 506         /* both buffers have identical glyph indices */
 507         hb_buffer_clear_contents(buf);
 508       }
 509     }
 510   }
 511
 512   *count = hb_buffer_get_length(buf);
 513
 514 #ifdef TA_DEBUG
 515   if (feature && *count > 1)
 516     TA_LOG(("ta_shaper_get_cluster:"
 517             " input character mapped to multiple glyphs\n"));
 518 #endif
 519
 520   return q;
 521 }
 522
 523
 524 FT_ULong
 525 ta_shaper_get_elem(TA_StyleMetrics metrics,
 526                    void* buf_,
 527                    unsigned int idx,
 528                    FT_Long* advance,
 529                    FT_Long* y_offset)
 530 {
 531   hb_buffer_t* buf = (hb_buffer_t*)buf_;
 532   hb_glyph_info_t* ginfo;
 533   hb_glyph_position_t* gpos;
 534   unsigned int gcount;
 535
 536   FT_UNUSED(metrics);
 537
 538
 539   ginfo = hb_buffer_get_glyph_infos(buf, &gcount);
 540   gpos = hb_buffer_get_glyph_positions(buf, &gcount);
 541
 542   if (idx >= gcount)
 543     return 0;
 544
 545   if (advance)
 546     *advance = gpos[idx].x_advance;
 547   if (y_offset)
 548     *y_offset = gpos[idx].y_offset;
 549
 550   return ginfo[idx].codepoint;
 551 }
 552
 553 /* end of tashaper.c */