lib/3rdparty/freetype/src/autofit/hbshim.c

   1 /***************************************************************************/
   2 /*                                                                         */
   3 /*  hbshim.c                                                               */
   4 /*                                                                         */
   5 /*    HarfBuzz interface for accessing OpenType features (body).           */
   6 /*                                                                         */
   7 /*  Copyright 2013, 2014 by                                                */
   8 /*  David Turner, Robert Wilhelm, and Werner Lemberg.                      */
   9 /*                                                                         */
  10 /*  This file is part of the FreeType project, and may only be used,       */
  11 /*  modified, and distributed under the terms of the FreeType project      */
  12 /*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
  13 /*  this file you indicate that you have read the license and              */
  14 /*  understand and accept it fully.                                        */
  15 /*                                                                         */
  16 /***************************************************************************/
  17
  18
  19 #include <ft2build.h>
  20 #include FT_FREETYPE_H
  21 #include "afglobal.h"
  22 #include "aftypes.h"
  23 #include "hbshim.h"
  24
  25 #ifdef FT_CONFIG_OPTION_USE_HARFBUZZ
  26
  27
  28   /*************************************************************************/
  29   /*                                                                       */
  30   /* The macro FT_COMPONENT is used in trace mode.  It is an implicit      */
  31   /* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log  */
  32   /* messages during execution.                                            */
  33   /*                                                                       */
  34 #undef  FT_COMPONENT
  35 #define FT_COMPONENT  trace_afharfbuzz
  36
  37
  38   /*
  39    * We use `sets' (in the HarfBuzz sense, which comes quite near to the
  40    * usual mathematical meaning) to manage both lookups and glyph indices.
  41    *
  42    * 1. For each coverage, collect lookup IDs in a set.  Note that an
  43    *    auto-hinter `coverage' is represented by one `feature', and a
  44    *    feature consists of an arbitrary number of (font specific) `lookup's
  45    *    that actually do the mapping job.  Please check the OpenType
  46    *    specification for more details on features and lookups.
  47    *
  48    * 2. Create glyph ID sets from the corresponding lookup sets.
  49    *
  50    * 3. The glyph set corresponding to AF_COVERAGE_DEFAULT is computed
  51    *    with all lookups specific to the OpenType script activated.  It
  52    *    relies on the order of AF_DEFINE_STYLE_CLASS entries so that
  53    *    special coverages (like `oldstyle figures') don't get overwritten.
  54    *
  55    */
  56
  57
  58   /* load coverage tags */
  59 #undef  COVERAGE
  60 #define COVERAGE( name, NAME, description,             \
  61                   tag1, tag2, tag3, tag4 )             \
  62           static const hb_tag_t  name ## _coverage[] = \
  63           {                                            \
  64             HB_TAG( tag1, tag2, tag3, tag4 ),          \
  65             HB_TAG_NONE                                \
  66           };
  67
  68
  69 #include "afcover.h"
  70
  71
  72   /* define mapping between coverage tags and AF_Coverage */
  73 #undef  COVERAGE
  74 #define COVERAGE( name, NAME, description, \
  75                   tag1, tag2, tag3, tag4 ) \
  76           name ## _coverage,
  77
  78
  79   static const hb_tag_t*  coverages[] =
  80   {
  81 #include "afcover.h"
  82
  83     NULL /* AF_COVERAGE_DEFAULT */
  84   };
  85
  86
  87   /* load HarfBuzz script tags */
  88 #undef  SCRIPT
  89 #define SCRIPT( s, S, d, h, sc1, sc2, sc3 )  h,
  90
  91
  92   static const hb_script_t  scripts[] =
  93   {
  94 #include "afscript.h"
  95   };
  96
  97
  98   FT_Error
  99   af_get_coverage( AF_FaceGlobals  globals,
 100                    AF_StyleClass   style_class,
 101                    FT_Byte*        gstyles )
 102   {
 103     hb_face_t*  face;
 104
 105     hb_set_t*  gsub_lookups;  /* GSUB lookups for a given script */
 106     hb_set_t*  gsub_glyphs;   /* glyphs covered by GSUB lookups  */
 107     hb_set_t*  gpos_lookups;  /* GPOS lookups for a given script */
 108     hb_set_t*  gpos_glyphs;   /* glyphs covered by GPOS lookups  */
 109
 110     hb_script_t      script;
 111     const hb_tag_t*  coverage_tags;
 112     hb_tag_t         script_tags[] = { HB_TAG_NONE,
 113                                        HB_TAG_NONE,
 114                                        HB_TAG_NONE,
 115                                        HB_TAG_NONE };
 116
 117     hb_codepoint_t  idx;
 118 #ifdef FT_DEBUG_LEVEL_TRACE
 119     int             count;
 120 #endif
 121
 122
 123     if ( !globals || !style_class || !gstyles )
 124       return FT_THROW( Invalid_Argument );
 125
 126     face = hb_font_get_face( globals->hb_font );
 127
 128     gsub_lookups = hb_set_create();
 129     gsub_glyphs  = hb_set_create();
 130     gpos_lookups = hb_set_create();
 131     gpos_glyphs  = hb_set_create();
 132
 133     coverage_tags = coverages[style_class->coverage];
 134     script        = scripts[style_class->script];
 135
 136     /* Convert a HarfBuzz script tag into the corresponding OpenType */
 137     /* tag or tags -- some Indic scripts like Devanagari have an old */
 138     /* and a new set of features.                                    */
 139     hb_ot_tags_from_script( script,
 140                             &script_tags[0],
 141                             &script_tags[1] );
 142
 143     /* `hb_ot_tags_from_script' usually returns HB_OT_TAG_DEFAULT_SCRIPT */
 144     /* as the second tag.  We change that to HB_TAG_NONE except for the  */
 145     /* default script.                                                   */
 146     if ( style_class->script == globals->module->default_script &&
 147          style_class->coverage == AF_COVERAGE_DEFAULT           )
 148     {
 149       if ( script_tags[0] == HB_TAG_NONE )
 150         script_tags[0] = HB_OT_TAG_DEFAULT_SCRIPT;
 151       else
 152       {
 153         if ( script_tags[1] == HB_TAG_NONE )
 154           script_tags[1] = HB_OT_TAG_DEFAULT_SCRIPT;
 155         else if ( script_tags[1] != HB_OT_TAG_DEFAULT_SCRIPT )
 156           script_tags[2] = HB_OT_TAG_DEFAULT_SCRIPT;
 157       }
 158     }
 159     else
 160     {
 161       if ( script_tags[1] == HB_OT_TAG_DEFAULT_SCRIPT )
 162         script_tags[1] = HB_TAG_NONE;
 163     }
 164
 165     hb_ot_layout_collect_lookups( face,
 166                                   HB_OT_TAG_GSUB,
 167                                   script_tags,
 168                                   NULL,
 169                                   coverage_tags,
 170                                   gsub_lookups );
 171
 172     if ( hb_set_is_empty( gsub_lookups ) )
 173       goto Exit; /* nothing to do */
 174
 175     hb_ot_layout_collect_lookups( face,
 176                                   HB_OT_TAG_GPOS,
 177                                   script_tags,
 178                                   NULL,
 179                                   coverage_tags,
 180                                   gpos_lookups );
 181
 182     FT_TRACE4(( "GSUB lookups (style `%s'):\n"
 183                 " ",
 184                 af_style_names[style_class->style] ));
 185
 186 #ifdef FT_DEBUG_LEVEL_TRACE
 187     count = 0;
 188 #endif
 189
 190     for ( idx = -1; hb_set_next( gsub_lookups, &idx ); )
 191     {
 192 #ifdef FT_DEBUG_LEVEL_TRACE
 193       FT_TRACE4(( " %d", idx ));
 194       count++;
 195 #endif
 196
 197       /* get output coverage of GSUB feature */
 198       hb_ot_layout_lookup_collect_glyphs( face,
 199                                           HB_OT_TAG_GSUB,
 200                                           idx,
 201                                           NULL,
 202                                           NULL,
 203                                           NULL,
 204                                           gsub_glyphs );
 205     }
 206
 207 #ifdef FT_DEBUG_LEVEL_TRACE
 208     if ( !count )
 209       FT_TRACE4(( " (none)" ));
 210     FT_TRACE4(( "\n\n" ));
 211 #endif
 212
 213     FT_TRACE4(( "GPOS lookups (style `%s'):\n"
 214                 " ",
 215                 af_style_names[style_class->style] ));
 216
 217 #ifdef FT_DEBUG_LEVEL_TRACE
 218     count = 0;
 219 #endif
 220
 221     for ( idx = -1; hb_set_next( gpos_lookups, &idx ); )
 222     {
 223 #ifdef FT_DEBUG_LEVEL_TRACE
 224       FT_TRACE4(( " %d", idx ));
 225       count++;
 226 #endif
 227
 228       /* get input coverage of GPOS feature */
 229       hb_ot_layout_lookup_collect_glyphs( face,
 230                                           HB_OT_TAG_GPOS,
 231                                           idx,
 232                                           NULL,
 233                                           gpos_glyphs,
 234                                           NULL,
 235                                           NULL );
 236     }
 237
 238 #ifdef FT_DEBUG_LEVEL_TRACE
 239     if ( !count )
 240       FT_TRACE4(( " (none)" ));
 241     FT_TRACE4(( "\n\n" ));
 242 #endif
 243
 244     /*
 245      * We now check whether we can construct blue zones, using glyphs
 246      * covered by the feature only.  In case there is not a single zone
 247      * (this is, not a single character is covered), we skip this coverage.
 248      *
 249      */
 250     {
 251       AF_Blue_Stringset         bss = style_class->blue_stringset;
 252       const AF_Blue_StringRec*  bs  = &af_blue_stringsets[bss];
 253
 254       FT_Bool  found = 0;
 255
 256
 257       for ( ; bs->string != AF_BLUE_STRING_MAX; bs++ )
 258       {
 259         const char*  p = &af_blue_strings[bs->string];
 260
 261
 262         while ( *p )
 263         {
 264           hb_codepoint_t  ch;
 265
 266
 267           GET_UTF8_CHAR( ch, p );
 268
 269           for ( idx = -1; hb_set_next( gsub_lookups, &idx ); )
 270           {
 271             hb_codepoint_t  gidx = FT_Get_Char_Index( globals->face, ch );
 272
 273
 274             if ( hb_ot_layout_lookup_would_substitute( face, idx,
 275                                                        &gidx, 1, 1 ) )
 276             {
 277               found = 1;
 278               break;
 279             }
 280           }
 281         }
 282       }
 283
 284       if ( !found )
 285       {
 286         FT_TRACE4(( "  no blue characters found; style skipped\n" ));
 287         goto Exit;
 288       }
 289     }
 290
 291     /*
 292      * Various OpenType features might use the same glyphs at different
 293      * vertical positions; for example, superscript and subscript glyphs
 294      * could be the same.  However, the auto-hinter is completely
 295      * agnostic of OpenType features after the feature analysis has been
 296      * completed: The engine then simply receives a glyph index and returns a
 297      * hinted and usually rendered glyph.
 298      *
 299      * Consider the superscript feature of font `pala.ttf': Some of the
 300      * glyphs are `real', this is, they have a zero vertical offset, but
 301      * most of them are small caps glyphs shifted up to the superscript
 302      * position (this is, the `sups' feature is present in both the GSUB and
 303      * GPOS tables).  The code for blue zones computation actually uses a
 304      * feature's y offset so that the `real' glyphs get correct hints.  But
 305      * later on it is impossible to decide whether a glyph index belongs to,
 306      * say, the small caps or superscript feature.
 307      *
 308      * For this reason, we don't assign a style to a glyph if the current
 309      * feature covers the glyph in both the GSUB and the GPOS tables.  This
 310      * is quite a broad condition, assuming that
 311      *
 312      *   (a) glyphs that get used in multiple features are present in a
 313      *       feature without vertical shift,
 314      *
 315      * and
 316      *
 317      *   (b) a feature's GPOS data really moves the glyph vertically.
 318      *
 319      * Not fulfilling condition (a) makes a font larger; it would also
 320      * reduce the number of glyphs that could be addressed directly without
 321      * using OpenType features, so this assumption is rather strong.
 322      *
 323      * Condition (b) is much weaker, and there might be glyphs which get
 324      * missed.  However, the OpenType features we are going to handle are
 325      * primarily located in GSUB, and HarfBuzz doesn't provide an API to
 326      * directly get the necessary information from the GPOS table.  A
 327      * possible solution might be to directly parse the GPOS table to find
 328      * out whether a glyph gets shifted vertically, but this is something I
 329      * would like to avoid if not really necessary.
 330      *
 331      */
 332     hb_set_subtract( gsub_glyphs, gpos_glyphs );
 333
 334 #ifdef FT_DEBUG_LEVEL_TRACE
 335     FT_TRACE4(( "  glyphs without GPOS data (`*' means already assigned)" ));
 336     count = 0;
 337 #endif
 338
 339     for ( idx = -1; hb_set_next( gsub_glyphs, &idx ); )
 340     {
 341 #ifdef FT_DEBUG_LEVEL_TRACE
 342       if ( !( count % 10 ) )
 343         FT_TRACE4(( "\n"
 344                     "   " ));
 345
 346       FT_TRACE4(( " %d", idx ));
 347       count++;
 348 #endif
 349
 350       if ( gstyles[idx] == AF_STYLE_UNASSIGNED )
 351         gstyles[idx] = (FT_Byte)style_class->style;
 352 #ifdef FT_DEBUG_LEVEL_TRACE
 353       else
 354         FT_TRACE4(( "*" ));
 355 #endif
 356     }
 357
 358 #ifdef FT_DEBUG_LEVEL_TRACE
 359     if ( !count )
 360       FT_TRACE4(( "\n"
 361                   "    (none)" ));
 362     FT_TRACE4(( "\n\n" ));
 363 #endif
 364
 365   Exit:
 366     hb_set_destroy( gsub_lookups );
 367     hb_set_destroy( gsub_glyphs  );
 368     hb_set_destroy( gpos_lookups );
 369     hb_set_destroy( gpos_glyphs  );
 370
 371     return FT_Err_Ok;
 372   }
 373
 374
 375   /* construct HarfBuzz features */
 376 #undef  COVERAGE
 377 #define COVERAGE( name, NAME, description,                \
 378                   tag1, tag2, tag3, tag4 )                \
 379           static const hb_feature_t  name ## _feature[] = \
 380           {                                               \
 381             {                                             \
 382               HB_TAG( tag1, tag2, tag3, tag4 ),           \
 383               1, 0, (unsigned int)-1                      \
 384             }                                             \
 385           };
 386
 387
 388 #include "afcover.h"
 389
 390
 391   /* define mapping between HarfBuzz features and AF_Coverage */
 392 #undef  COVERAGE
 393 #define COVERAGE( name, NAME, description, \
 394                   tag1, tag2, tag3, tag4 ) \
 395           name ## _feature,
 396
 397
 398   static const hb_feature_t*  features[] =
 399   {
 400 #include "afcover.h"
 401
 402     NULL /* AF_COVERAGE_DEFAULT */
 403   };
 404
 405
 406   FT_Error
 407   af_get_char_index( AF_StyleMetrics  metrics,
 408                      FT_ULong         charcode,
 409                      FT_ULong        *codepoint,
 410                      FT_Long         *y_offset )
 411   {
 412     AF_StyleClass  style_class;
 413
 414     const hb_feature_t*  feature;
 415
 416     FT_ULong  in_idx, out_idx;
 417
 418
 419     if ( !metrics )
 420       return FT_THROW( Invalid_Argument );
 421
 422     in_idx = FT_Get_Char_Index( metrics->globals->face, charcode );
 423
 424     style_class = metrics->style_class;
 425
 426     feature = features[style_class->coverage];
 427
 428     if ( feature )
 429     {
 430       FT_UInt  upem = metrics->globals->face->units_per_EM;
 431
 432       hb_font_t*    font = metrics->globals->hb_font;
 433       hb_buffer_t*  buf  = hb_buffer_create();
 434
 435       uint32_t  c = (uint32_t)charcode;
 436
 437       hb_glyph_info_t*      ginfo;
 438       hb_glyph_position_t*  gpos;
 439       unsigned int          gcount;
 440
 441
 442       /* we shape at a size of units per EM; this means font units */
 443       hb_font_set_scale( font, upem, upem );
 444
 445       /* XXX: is this sufficient for a single character of any script? */
 446       hb_buffer_set_direction( buf, HB_DIRECTION_LTR );
 447       hb_buffer_set_script( buf, scripts[style_class->script] );
 448
 449       /* we add one character to `buf' ... */
 450       hb_buffer_add_utf32( buf, &c, 1, 0, 1 );
 451
 452       /* ... and apply one feature */
 453       hb_shape( font, buf, feature, 1 );
 454
 455       ginfo = hb_buffer_get_glyph_infos( buf, &gcount );
 456       gpos  = hb_buffer_get_glyph_positions( buf, &gcount );
 457
 458       out_idx = ginfo[0].codepoint;
 459
 460       /* getting the same index indicates no substitution,         */
 461       /* which means that the glyph isn't available in the feature */
 462       if ( in_idx == out_idx )
 463       {
 464         *codepoint = 0;
 465         *y_offset  = 0;
 466       }
 467       else
 468       {
 469         *codepoint = out_idx;
 470         *y_offset  = gpos[0].y_offset;
 471       }
 472
 473       hb_buffer_destroy( buf );
 474
 475 #ifdef FT_DEBUG_LEVEL_TRACE
 476       if ( gcount > 1 )
 477         FT_TRACE1(( "af_get_char_index:"
 478                     " input character mapped to multiple glyphs\n" ));
 479 #endif
 480     }
 481     else
 482     {
 483       *codepoint = in_idx;
 484       *y_offset  = 0;
 485     }
 486
 487     return FT_Err_Ok;
 488   }
 489
 490
 491 #else /* !FT_CONFIG_OPTION_USE_HARFBUZZ */
 492
 493
 494   FT_Error
 495   af_get_coverage( AF_FaceGlobals  globals,
 496                    AF_StyleClass   style_class,
 497                    FT_Byte*        gstyles )
 498   {
 499     FT_UNUSED( globals );
 500     FT_UNUSED( style_class );
 501     FT_UNUSED( gstyles );
 502
 503     return FT_Err_Ok;
 504   }
 505
 506
 507   FT_Error
 508   af_get_char_index( AF_StyleMetrics  metrics,
 509                      FT_ULong         charcode,
 510                      FT_ULong        *codepoint,
 511                      FT_Long         *y_offset )
 512   {
 513     FT_Face  face;
 514
 515
 516     if ( !metrics )
 517       return FT_THROW( Invalid_Argument );
 518
 519     face = metrics->globals->face;
 520
 521     *codepoint = FT_Get_Char_Index( face, charcode );
 522     *y_offset  = 0;
 523
 524     return FT_Err_Ok;
 525   }
 526
 527
 528 #endif /* !FT_CONFIG_OPTION_USE_HARFBUZZ */
 529
 530
 531 /* END */