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 if ( style_class->coverage != AF_COVERAGE_DEFAULT ) 251 { 252 AF_Blue_Stringset bss = style_class->blue_stringset; 253 const AF_Blue_StringRec* bs = &af_blue_stringsets[bss]; 254 255 FT_Bool found = 0; 256 257 258 for ( ; bs->string != AF_BLUE_STRING_MAX; bs++ ) 259 { 260 const char* p = &af_blue_strings[bs->string]; 261 262 263 while ( *p ) 264 { 265 hb_codepoint_t ch; 266 267 268 GET_UTF8_CHAR( ch, p ); 269 270 for ( idx = -1; hb_set_next( gsub_lookups, &idx ); ) 271 { 272 hb_codepoint_t gidx = FT_Get_Char_Index( globals->face, ch ); 273 274 275 if ( hb_ot_layout_lookup_would_substitute( face, idx, 276 &gidx, 1, 1 ) ) 277 { 278 found = 1; 279 break; 280 } 281 } 282 } 283 } 284 285 if ( !found ) 286 { 287 FT_TRACE4(( " no blue characters found; style skipped\n" )); 288 goto Exit; 289 } 290 } 291 292 /* 293 * Various OpenType features might use the same glyphs at different 294 * vertical positions; for example, superscript and subscript glyphs 295 * could be the same. However, the auto-hinter is completely 296 * agnostic of OpenType features after the feature analysis has been 297 * completed: The engine then simply receives a glyph index and returns a 298 * hinted and usually rendered glyph. 299 * 300 * Consider the superscript feature of font `pala.ttf': Some of the 301 * glyphs are `real', this is, they have a zero vertical offset, but 302 * most of them are small caps glyphs shifted up to the superscript 303 * position (this is, the `sups' feature is present in both the GSUB and 304 * GPOS tables). The code for blue zones computation actually uses a 305 * feature's y offset so that the `real' glyphs get correct hints. But 306 * later on it is impossible to decide whether a glyph index belongs to, 307 * say, the small caps or superscript feature. 308 * 309 * For this reason, we don't assign a style to a glyph if the current 310 * feature covers the glyph in both the GSUB and the GPOS tables. This 311 * is quite a broad condition, assuming that 312 * 313 * (a) glyphs that get used in multiple features are present in a 314 * feature without vertical shift, 315 * 316 * and 317 * 318 * (b) a feature's GPOS data really moves the glyph vertically. 319 * 320 * Not fulfilling condition (a) makes a font larger; it would also 321 * reduce the number of glyphs that could be addressed directly without 322 * using OpenType features, so this assumption is rather strong. 323 * 324 * Condition (b) is much weaker, and there might be glyphs which get 325 * missed. However, the OpenType features we are going to handle are 326 * primarily located in GSUB, and HarfBuzz doesn't provide an API to 327 * directly get the necessary information from the GPOS table. A 328 * possible solution might be to directly parse the GPOS table to find 329 * out whether a glyph gets shifted vertically, but this is something I 330 * would like to avoid if not really necessary. 331 * 332 * Note that we don't follow this logic for the default coverage. 333 * Complex scripts like Devanagari have mandatory GPOS features to 334 * position many glyph elements, using mark-to-base or mark-to-ligature 335 * tables; the number of glyphs missed due to condition (b) would be far 336 * too large. 337 * 338 */ 339 if ( style_class->coverage != AF_COVERAGE_DEFAULT ) 340 hb_set_subtract( gsub_glyphs, gpos_glyphs ); 341 342 #ifdef FT_DEBUG_LEVEL_TRACE 343 FT_TRACE4(( " glyphs without GPOS data (`*' means already assigned)" )); 344 count = 0; 345 #endif 346 347 for ( idx = -1; hb_set_next( gsub_glyphs, &idx ); ) 348 { 349 #ifdef FT_DEBUG_LEVEL_TRACE 350 if ( !( count % 10 ) ) 351 FT_TRACE4(( "\n" 352 " " )); 353 354 FT_TRACE4(( " %d", idx )); 355 count++; 356 #endif 357 358 /* glyph indices returned by `hb_ot_layout_lookup_collect_glyphs' */ 359 /* can be arbitrary: some fonts use fake indices for processing */ 360 /* internal to GSUB or GPOS, which is fully valid */ 361 if ( idx >= (hb_codepoint_t)globals->glyph_count ) 362 continue; 363 364 if ( gstyles[idx] == AF_STYLE_UNASSIGNED ) 365 gstyles[idx] = (FT_Byte)style_class->style; 366 #ifdef FT_DEBUG_LEVEL_TRACE 367 else 368 FT_TRACE4(( "*" )); 369 #endif 370 } 371 372 #ifdef FT_DEBUG_LEVEL_TRACE 373 if ( !count ) 374 FT_TRACE4(( "\n" 375 " (none)" )); 376 FT_TRACE4(( "\n\n" )); 377 #endif 378 379 Exit: 380 hb_set_destroy( gsub_lookups ); 381 hb_set_destroy( gsub_glyphs ); 382 hb_set_destroy( gpos_lookups ); 383 hb_set_destroy( gpos_glyphs ); 384 385 return FT_Err_Ok; 386 } 387 388 389 /* construct HarfBuzz features */ 390 #undef COVERAGE 391 #define COVERAGE( name, NAME, description, \ 392 tag1, tag2, tag3, tag4 ) \ 393 static const hb_feature_t name ## _feature[] = \ 394 { \ 395 { \ 396 HB_TAG( tag1, tag2, tag3, tag4 ), \ 397 1, 0, (unsigned int)-1 \ 398 } \ 399 }; 400 401 402 #include "afcover.h" 403 404 405 /* define mapping between HarfBuzz features and AF_Coverage */ 406 #undef COVERAGE 407 #define COVERAGE( name, NAME, description, \ 408 tag1, tag2, tag3, tag4 ) \ 409 name ## _feature, 410 411 412 static const hb_feature_t* features[] = 413 { 414 #include "afcover.h" 415 416 NULL /* AF_COVERAGE_DEFAULT */ 417 }; 418 419 420 FT_Error 421 af_get_char_index( AF_StyleMetrics metrics, 422 FT_ULong charcode, 423 FT_ULong *codepoint, 424 FT_Long *y_offset ) 425 { 426 AF_StyleClass style_class; 427 428 const hb_feature_t* feature; 429 430 FT_ULong in_idx, out_idx; 431 432 433 if ( !metrics ) 434 return FT_THROW( Invalid_Argument ); 435 436 in_idx = FT_Get_Char_Index( metrics->globals->face, charcode ); 437 438 style_class = metrics->style_class; 439 440 feature = features[style_class->coverage]; 441 442 if ( feature ) 443 { 444 FT_UInt upem = metrics->globals->face->units_per_EM; 445 446 hb_font_t* font = metrics->globals->hb_font; 447 hb_buffer_t* buf = hb_buffer_create(); 448 449 uint32_t c = (uint32_t)charcode; 450 451 hb_glyph_info_t* ginfo; 452 hb_glyph_position_t* gpos; 453 unsigned int gcount; 454 455 456 /* we shape at a size of units per EM; this means font units */ 457 hb_font_set_scale( font, upem, upem ); 458 459 /* XXX: is this sufficient for a single character of any script? */ 460 hb_buffer_set_direction( buf, HB_DIRECTION_LTR ); 461 hb_buffer_set_script( buf, scripts[style_class->script] ); 462 463 /* we add one character to `buf' ... */ 464 hb_buffer_add_utf32( buf, &c, 1, 0, 1 ); 465 466 /* ... and apply one feature */ 467 hb_shape( font, buf, feature, 1 ); 468 469 ginfo = hb_buffer_get_glyph_infos( buf, &gcount ); 470 gpos = hb_buffer_get_glyph_positions( buf, &gcount ); 471 472 out_idx = ginfo[0].codepoint; 473 474 /* getting the same index indicates no substitution, */ 475 /* which means that the glyph isn't available in the feature */ 476 if ( in_idx == out_idx ) 477 { 478 *codepoint = 0; 479 *y_offset = 0; 480 } 481 else 482 { 483 *codepoint = out_idx; 484 *y_offset = gpos[0].y_offset; 485 } 486 487 hb_buffer_destroy( buf ); 488 489 #ifdef FT_DEBUG_LEVEL_TRACE 490 if ( gcount > 1 ) 491 FT_TRACE1(( "af_get_char_index:" 492 " input character mapped to multiple glyphs\n" )); 493 #endif 494 } 495 else 496 { 497 *codepoint = in_idx; 498 *y_offset = 0; 499 } 500 501 return FT_Err_Ok; 502 } 503 504 505 #else /* !FT_CONFIG_OPTION_USE_HARFBUZZ */ 506 507 508 FT_Error 509 af_get_coverage( AF_FaceGlobals globals, 510 AF_StyleClass style_class, 511 FT_Byte* gstyles ) 512 { 513 FT_UNUSED( globals ); 514 FT_UNUSED( style_class ); 515 FT_UNUSED( gstyles ); 516 517 return FT_Err_Ok; 518 } 519 520 521 FT_Error 522 af_get_char_index( AF_StyleMetrics metrics, 523 FT_ULong charcode, 524 FT_ULong *codepoint, 525 FT_Long *y_offset ) 526 { 527 FT_Face face; 528 529 530 if ( !metrics ) 531 return FT_THROW( Invalid_Argument ); 532 533 face = metrics->globals->face; 534 535 *codepoint = FT_Get_Char_Index( face, charcode ); 536 *y_offset = 0; 537 538 return FT_Err_Ok; 539 } 540 541 542 #endif /* !FT_CONFIG_OPTION_USE_HARFBUZZ */ 543 544 545 /* END */ 546
