lib/tashaper.c

   1 /* tashaper.c */
   2
   3 /*
   4  * Copyright (C) 2014-2016 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_Bool default_script)
  84 {
  85   hb_face_t* face;
  86
  87   hb_set_t* gsub_lookups; /* GSUB lookups for a given script */
  88   hb_set_t* gsub_glyphs; /* glyphs covered by GSUB lookups */
  89   hb_set_t* gpos_lookups; /* GPOS lookups for a given script */
  90   hb_set_t* gpos_glyphs; /* glyphs covered by GPOS lookups */
  91
  92   hb_script_t script;
  93   const hb_tag_t* coverage_tags;
  94   hb_tag_t script_tags[] = { HB_TAG_NONE,
  95                              HB_TAG_NONE,
  96                              HB_TAG_NONE,
  97                              HB_TAG_NONE };
  98
  99   hb_codepoint_t idx;
 100 #ifdef TA_DEBUG
 101   int count;
 102 #endif
 103
 104
 105   if (!globals || !style_class || !gstyles)
 106     return FT_Err_Invalid_Argument;
 107
 108   face = hb_font_get_face(globals->hb_font);
 109
 110   gsub_lookups = hb_set_create();
 111   gsub_glyphs = hb_set_create();
 112   gpos_lookups = hb_set_create();
 113   gpos_glyphs = hb_set_create();
 114
 115   coverage_tags = coverages[style_class->coverage];
 116   script = scripts[style_class->script];
 117
 118   /* convert a HarfBuzz script tag into the corresponding OpenType */
 119   /* tag or tags -- some Indic scripts like Devanagari have an old */
 120   /* and a new set of features */
 121   hb_ot_tags_from_script(script,
 122                          &script_tags[0],
 123                          &script_tags[1]);
 124
 125   /* `hb_ot_tags_from_script' usually returns HB_OT_TAG_DEFAULT_SCRIPT */
 126   /* as the second tag; we change that to HB_TAG_NONE except for the */
 127   /* default script */
 128   if (default_script)
 129   {
 130     if (script_tags[0] == HB_TAG_NONE)
 131       script_tags[0] = HB_OT_TAG_DEFAULT_SCRIPT;
 132     else
 133     {
 134       if (script_tags[1] == HB_TAG_NONE)
 135         script_tags[1] = HB_OT_TAG_DEFAULT_SCRIPT;
 136       else if (script_tags[1] != HB_OT_TAG_DEFAULT_SCRIPT)
 137         script_tags[2] = HB_OT_TAG_DEFAULT_SCRIPT;
 138     }
 139   }
 140   else
 141   {
 142     /* we use non-standard tags like `khms' for special purposes; */
 143     /* HarfBuzz maps them to `DFLT', which we don't want to handle here */
 144     if (script_tags[0] == HB_OT_TAG_DEFAULT_SCRIPT)
 145       goto Exit;
 146
 147     if (script_tags[1] == HB_OT_TAG_DEFAULT_SCRIPT)
 148       script_tags[1] = HB_TAG_NONE;
 149   }
 150
 151   hb_ot_layout_collect_lookups(face,
 152                                HB_OT_TAG_GSUB,
 153                                script_tags,
 154                                NULL,
 155                                coverage_tags,
 156                                gsub_lookups);
 157
 158   if (hb_set_is_empty(gsub_lookups))
 159     goto Exit; /* nothing to do */
 160
 161   hb_ot_layout_collect_lookups(face,
 162                                HB_OT_TAG_GPOS,
 163                                script_tags,
 164                                NULL,
 165                                coverage_tags,
 166                                gpos_lookups);
 167
 168   TA_LOG_GLOBAL(("GSUB lookups (style `%s'):\n"
 169                  " ",
 170                  ta_style_names[style_class->style]));
 171
 172 #ifdef TA_DEBUG
 173   count = 0;
 174 #endif
 175
 176   for (idx = HB_SET_VALUE_INVALID; hb_set_next(gsub_lookups, &idx);)
 177   {
 178 #ifdef TA_DEBUG
 179     TA_LOG_GLOBAL((" %d", idx));
 180     count++;
 181 #endif
 182
 183     /* get output coverage of GSUB feature */
 184     hb_ot_layout_lookup_collect_glyphs(face,
 185                                        HB_OT_TAG_GSUB,
 186                                        idx,
 187                                        NULL,
 188                                        NULL,
 189                                        NULL,
 190                                        gsub_glyphs);
 191   }
 192
 193 #ifdef TA_DEBUG
 194   if (!count)
 195     TA_LOG_GLOBAL((" (none)"));
 196   TA_LOG_GLOBAL(("\n\n"));
 197 #endif
 198
 199   TA_LOG_GLOBAL(("GPOS lookups (style `%s'):\n"
 200                  " ",
 201                  ta_style_names[style_class->style]));
 202
 203 #ifdef TA_DEBUG
 204   count = 0;
 205 #endif
 206
 207   for (idx = HB_SET_VALUE_INVALID; hb_set_next(gpos_lookups, &idx);)
 208   {
 209 #ifdef TA_DEBUG
 210     TA_LOG_GLOBAL((" %d", idx));
 211     count++;
 212 #endif
 213
 214     /* get input coverage of GPOS feature */
 215     hb_ot_layout_lookup_collect_glyphs(face,
 216                                        HB_OT_TAG_GPOS,
 217                                        idx,
 218                                        NULL,
 219                                        gpos_glyphs,
 220                                        NULL,
 221                                        NULL);
 222   }
 223
 224 #ifdef TA_DEBUG
 225   if (!count)
 226     TA_LOG_GLOBAL((" (none)"));
 227   TA_LOG_GLOBAL(("\n\n"));
 228 #endif
 229
 230   /*
 231    * we now check whether we can construct blue zones, using glyphs
 232    * covered by the feature only -- in case there is not a single zone
 233    * (this is, not a single character is covered), we skip this coverage
 234    */
 235   if (style_class->coverage != TA_COVERAGE_DEFAULT)
 236   {
 237     TA_Blue_Stringset bss = style_class->blue_stringset;
 238     const TA_Blue_StringRec* bs = &ta_blue_stringsets[bss];
 239
 240     FT_Bool found = 0;
 241
 242
 243     for (; bs->string != TA_BLUE_STRING_MAX; bs++)
 244     {
 245       const char* p = &ta_blue_strings[bs->string];
 246
 247
 248       while (*p)
 249       {
 250         hb_codepoint_t ch;
 251
 252
 253         GET_UTF8_CHAR(ch, p);
 254
 255         for (idx = HB_SET_VALUE_INVALID; hb_set_next(gsub_lookups, &idx);)
 256         {
 257           hb_codepoint_t gidx = FT_Get_Char_Index(globals->face, ch);
 258
 259
 260           if (hb_ot_layout_lookup_would_substitute(face, idx,
 261                                                    &gidx, 1, 1))
 262           {
 263             found = 1;
 264             break;
 265           }
 266         }
 267       }
 268     }
 269
 270     if (!found)
 271     {
 272       TA_LOG_GLOBAL(("  no blue characters found; style skipped\n"));
 273       goto Exit;
 274     }
 275   }
 276
 277   /*
 278    * Various OpenType features might use the same glyphs at different
 279    * vertical positions; for example, superscript and subscript glyphs
 280    * could be the same.  However, the auto-hinter is completely
 281    * agnostic of OpenType features after the feature analysis has been
 282    * completed: The engine then simply receives a glyph index and returns a
 283    * hinted and usually rendered glyph.
 284    *
 285    * Consider the superscript feature of font `pala.ttf': Some of the
 286    * glyphs are `real', this is, they have a zero vertical offset, but
 287    * most of them are small caps glyphs shifted up to the superscript
 288    * position (this is, the `sups' feature is present in both the GSUB and
 289    * GPOS tables).  The code for blue zones computation actually uses a
 290    * feature's y offset so that the `real' glyphs get correct hints.  But
 291    * later on it is impossible to decide whether a glyph index belongs to,
 292    * say, the small caps or superscript feature.
 293    *
 294    * For this reason, we don't assign a style to a glyph if the current
 295    * feature covers the glyph in both the GSUB and the GPOS tables.  This
 296    * is quite a broad condition, assuming that
 297    *
 298    *   (a) glyphs that get used in multiple features are present in a
 299    *       feature without vertical shift,
 300    *
 301    * and
 302    *
 303    *   (b) a feature's GPOS data really moves the glyph vertically.
 304    *
 305    * Not fulfilling condition (a) makes a font larger; it would also
 306    * reduce the number of glyphs that could be addressed directly without
 307    * using OpenType features, so this assumption is rather strong.
 308    *
 309    * Condition (b) is much weaker, and there might be glyphs which get
 310    * missed.  However, the OpenType features we are going to handle are
 311    * primarily located in GSUB, and HarfBuzz doesn't provide an API to
 312    * directly get the necessary information from the GPOS table.  A
 313    * possible solution might be to directly parse the GPOS table to find
 314    * out whether a glyph gets shifted vertically, but this is something I
 315    * would like to avoid if not really necessary.
 316    *
 317    * Note that we don't follow this logic for the default coverage.
 318    * Complex scripts like Devanagari have mandatory GPOS features to
 319    * position many glyph elements, using mark-to-base or mark-to-ligature
 320    * tables; the number of glyphs missed due to condition (b) would be far
 321    * too large.
 322    */
 323   if (style_class->coverage != TA_COVERAGE_DEFAULT)
 324     hb_set_subtract(gsub_glyphs, gpos_glyphs);
 325
 326 #ifdef TA_DEBUG
 327   TA_LOG_GLOBAL(("  glyphs without GPOS data (`*' means already assigned)"));
 328   count = 0;
 329 #endif
 330
 331   for (idx = HB_SET_VALUE_INVALID; hb_set_next(gsub_glyphs, &idx);)
 332   {
 333 #ifdef TA_DEBUG
 334     if (!(count % 10))
 335       TA_LOG_GLOBAL(("\n"
 336                      "   "));
 337
 338     TA_LOG_GLOBAL((" %d", idx));
 339     count++;
 340 #endif
 341
 342     /* glyph indices returned by `hb_ot_layout_lookup_collect_glyphs' */
 343     /* can be arbitrary: some fonts use fake indices for processing */
 344     /* internal to GSUB or GPOS, which is fully valid */
 345     if (idx >= (hb_codepoint_t)globals->glyph_count)
 346       continue;
 347
 348     if (gstyles[idx] == TA_STYLE_UNASSIGNED)
 349       gstyles[idx] = (FT_UShort)style_class->style;
 350 #ifdef TA_DEBUG
 351     else
 352       TA_LOG_GLOBAL(("*"));
 353 #endif
 354   }
 355
 356 #ifdef TA_DEBUG
 357     if (!count)
 358       TA_LOG_GLOBAL(("\n"
 359                      "    (none)"));
 360     TA_LOG_GLOBAL(("\n\n"));
 361 #endif
 362
 363 Exit:
 364   hb_set_destroy(gsub_lookups);
 365   hb_set_destroy(gsub_glyphs);
 366   hb_set_destroy(gpos_lookups);
 367   hb_set_destroy(gpos_glyphs);
 368
 369   return FT_Err_Ok;
 370 }
 371
 372
 373 /* construct HarfBuzz features */
 374 #undef COVERAGE
 375 #define COVERAGE(name, NAME, description, \
 376                  tag, tag1, tag2, tag3, tag4) \
 377           static const hb_feature_t name ## _feature[] = \
 378           { \
 379             { \
 380               HB_TAG(tag1, tag2, tag3, tag4), \
 381               1, 0, (unsigned int)-1 \
 382             } \
 383           };
 384
 385 #include "ttfautohint-coverages.h"
 386
 387
 388 /* define mapping between HarfBuzz features and TA_Coverage */
 389 #undef COVERAGE
 390 #define COVERAGE(name, NAME, description, \
 391                  tag, tag1, tag2, tag3, tag4) \
 392           name ## _feature,
 393
 394 static const hb_feature_t* features[] =
 395 {
 396 #include "ttfautohint-coverages.h"
 397
 398   NULL /* TA_COVERAGE_DEFAULT */
 399 };
 400
 401
 402 void*
 403 ta_shaper_buf_create(FT_Face face)
 404 {
 405   FT_UNUSED(face);
 406
 407   return (void*)hb_buffer_create();
 408 }
 409
 410
 411 void
 412 ta_shaper_buf_destroy(FT_Face face,
 413                       void* buf)
 414 {
 415   FT_UNUSED(face);
 416
 417   hb_buffer_destroy((hb_buffer_t*)buf);
 418 }
 419
 420
 421 const char*
 422 ta_shaper_get_cluster(const char* p,
 423                       TA_StyleMetrics metrics,
 424                       void* buf_,
 425                       unsigned int* count)
 426 {
 427   TA_StyleClass style_class;
 428   const hb_feature_t* feature;
 429   FT_Int upem;
 430   const char* q;
 431   int len;
 432
 433   hb_buffer_t* buf = (hb_buffer_t*)buf_;
 434   hb_font_t* font;
 435   hb_codepoint_t dummy;
 436
 437
 438   upem = (FT_Int)metrics->globals->face->units_per_EM;
 439   style_class = metrics->style_class;
 440   feature = features[style_class->coverage];
 441
 442   font = metrics->globals->hb_font;
 443
 444   /* we shape at a size of units per EM; this means font units */
 445   hb_font_set_scale(font, upem, upem);
 446
 447   while (*p == ' ')
 448     p++;
 449
 450   /* count bytes up to next space (or end of buffer) */
 451   q = p;
 452   while (!(*q == ' ' || *q == '\0'))
 453     GET_UTF8_CHAR(dummy, q);
 454   len = (int)(q - p);
 455
 456   /* feed character(s) to the HarfBuzz buffer */
 457   hb_buffer_clear_contents(buf);
 458   hb_buffer_add_utf8(buf, p, len, 0, len);
 459
 460   /* we let HarfBuzz guess the script and writing direction */
 461   hb_buffer_guess_segment_properties(buf);
 462
 463   /* shape buffer, which means conversion from character codes to */
 464   /* glyph indices, possibly applying a feature                   */
 465   hb_shape(font, buf, feature, feature ? 1 : 0);
 466
 467   if (feature)
 468   {
 469     hb_buffer_t* hb_buf = metrics->globals->hb_buf;
 470
 471     unsigned int gcount;
 472     hb_glyph_info_t* ginfo;
 473
 474     unsigned int hb_gcount;
 475     hb_glyph_info_t* hb_ginfo;
 476
 477
 478     /* we have to check whether applying a feature does actually change */
 479     /* glyph indices; otherwise the affected glyph or glyphs aren't */
 480     /* available at all in the feature */
 481
 482     hb_buffer_clear_contents(hb_buf);
 483     hb_buffer_add_utf8(hb_buf, p, len, 0, len);
 484     hb_buffer_guess_segment_properties(hb_buf);
 485     hb_shape(font, hb_buf, NULL, 0);
 486
 487     ginfo = hb_buffer_get_glyph_infos(buf, &gcount);
 488     hb_ginfo = hb_buffer_get_glyph_infos(hb_buf, &hb_gcount);
 489
 490     if (gcount == hb_gcount)
 491     {
 492       unsigned int i;
 493
 494
 495       for (i = 0; i < gcount; i++)
 496         if (ginfo[i].codepoint != hb_ginfo[i].codepoint)
 497           break;
 498
 499       if (i == gcount)
 500       {
 501         /* both buffers have identical glyph indices */
 502         hb_buffer_clear_contents(buf);
 503       }
 504     }
 505   }
 506
 507   *count = hb_buffer_get_length(buf);
 508
 509 #ifdef TA_DEBUG
 510   if (feature && *count > 1)
 511     TA_LOG(("ta_shaper_get_cluster:"
 512             " input character mapped to multiple glyphs\n"));
 513 #endif
 514
 515   return q;
 516 }
 517
 518
 519 FT_ULong
 520 ta_shaper_get_elem(TA_StyleMetrics metrics,
 521                    void* buf_,
 522                    unsigned int idx,
 523                    FT_Long* advance,
 524                    FT_Long* y_offset)
 525 {
 526   hb_buffer_t* buf = (hb_buffer_t*)buf_;
 527   hb_glyph_info_t* ginfo;
 528   hb_glyph_position_t* gpos;
 529   unsigned int gcount;
 530
 531   FT_UNUSED(metrics);
 532
 533
 534   ginfo = hb_buffer_get_glyph_infos(buf, &gcount);
 535   gpos = hb_buffer_get_glyph_positions(buf, &gcount);
 536
 537   if (idx >= gcount)
 538     return 0;
 539
 540   if (advance)
 541     *advance = gpos[idx].x_advance;
 542   if (y_offset)
 543     *y_offset = gpos[idx].y_offset;
 544
 545   return ginfo[idx].codepoint;
 546 }
 547
 548 /* end of tashaper.c */