hb-ot-shaper-thai.cc (12169B)
1 /* 2 * Copyright © 2010,2012 Google, Inc. 3 * 4 * This is part of HarfBuzz, a text shaping 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 * Google Author(s): Behdad Esfahbod 25 */ 26 27 #include "hb.hh" 28 29 #ifndef HB_NO_OT_SHAPE 30 31 #include "hb-ot-shaper.hh" 32 33 34 /* Thai / Lao shaper */ 35 36 37 /* PUA shaping */ 38 39 40 enum thai_consonant_type_t 41 { 42 NC, 43 AC, 44 RC, 45 DC, 46 NOT_CONSONANT, 47 NUM_CONSONANT_TYPES = NOT_CONSONANT 48 }; 49 50 static thai_consonant_type_t 51 get_consonant_type (hb_codepoint_t u) 52 { 53 if (u == 0x0E1Bu || u == 0x0E1Du || u == 0x0E1Fu/* || u == 0x0E2Cu*/) 54 return AC; 55 if (u == 0x0E0Du || u == 0x0E10u) 56 return RC; 57 if (u == 0x0E0Eu || u == 0x0E0Fu) 58 return DC; 59 if (hb_in_range<hb_codepoint_t> (u, 0x0E01u, 0x0E2Eu)) 60 return NC; 61 return NOT_CONSONANT; 62 } 63 64 65 enum thai_mark_type_t 66 { 67 AV, 68 BV, 69 T, 70 NOT_MARK, 71 NUM_MARK_TYPES = NOT_MARK 72 }; 73 74 static thai_mark_type_t 75 get_mark_type (hb_codepoint_t u) 76 { 77 if (u == 0x0E31u || hb_in_range<hb_codepoint_t> (u, 0x0E34u, 0x0E37u) || 78 u == 0x0E47u || hb_in_range<hb_codepoint_t> (u, 0x0E4Du, 0x0E4Eu)) 79 return AV; 80 if (hb_in_range<hb_codepoint_t> (u, 0x0E38u, 0x0E3Au)) 81 return BV; 82 if (hb_in_range<hb_codepoint_t> (u, 0x0E48u, 0x0E4Cu)) 83 return T; 84 return NOT_MARK; 85 } 86 87 88 enum thai_action_t 89 { 90 NOP, 91 SD, /* Shift combining-mark down */ 92 SL, /* Shift combining-mark left */ 93 SDL, /* Shift combining-mark down-left */ 94 RD /* Remove descender from base */ 95 }; 96 97 static hb_codepoint_t 98 thai_pua_shape (hb_codepoint_t u, thai_action_t action, hb_font_t *font) 99 { 100 struct thai_pua_mapping_t { 101 uint16_t u; 102 uint16_t win_pua; 103 uint16_t mac_pua; 104 } const *pua_mappings = nullptr; 105 static const thai_pua_mapping_t SD_mappings[] = { 106 {0x0E48u, 0xF70Au, 0xF88Bu}, /* MAI EK */ 107 {0x0E49u, 0xF70Bu, 0xF88Eu}, /* MAI THO */ 108 {0x0E4Au, 0xF70Cu, 0xF891u}, /* MAI TRI */ 109 {0x0E4Bu, 0xF70Du, 0xF894u}, /* MAI CHATTAWA */ 110 {0x0E4Cu, 0xF70Eu, 0xF897u}, /* THANTHAKHAT */ 111 {0x0E38u, 0xF718u, 0xF89Bu}, /* SARA U */ 112 {0x0E39u, 0xF719u, 0xF89Cu}, /* SARA UU */ 113 {0x0E3Au, 0xF71Au, 0xF89Du}, /* PHINTHU */ 114 {0x0000u, 0x0000u, 0x0000u} 115 }; 116 static const thai_pua_mapping_t SDL_mappings[] = { 117 {0x0E48u, 0xF705u, 0xF88Cu}, /* MAI EK */ 118 {0x0E49u, 0xF706u, 0xF88Fu}, /* MAI THO */ 119 {0x0E4Au, 0xF707u, 0xF892u}, /* MAI TRI */ 120 {0x0E4Bu, 0xF708u, 0xF895u}, /* MAI CHATTAWA */ 121 {0x0E4Cu, 0xF709u, 0xF898u}, /* THANTHAKHAT */ 122 {0x0000u, 0x0000u, 0x0000u} 123 }; 124 static const thai_pua_mapping_t SL_mappings[] = { 125 {0x0E48u, 0xF713u, 0xF88Au}, /* MAI EK */ 126 {0x0E49u, 0xF714u, 0xF88Du}, /* MAI THO */ 127 {0x0E4Au, 0xF715u, 0xF890u}, /* MAI TRI */ 128 {0x0E4Bu, 0xF716u, 0xF893u}, /* MAI CHATTAWA */ 129 {0x0E4Cu, 0xF717u, 0xF896u}, /* THANTHAKHAT */ 130 {0x0E31u, 0xF710u, 0xF884u}, /* MAI HAN-AKAT */ 131 {0x0E34u, 0xF701u, 0xF885u}, /* SARA I */ 132 {0x0E35u, 0xF702u, 0xF886u}, /* SARA II */ 133 {0x0E36u, 0xF703u, 0xF887u}, /* SARA UE */ 134 {0x0E37u, 0xF704u, 0xF888u}, /* SARA UEE */ 135 {0x0E47u, 0xF712u, 0xF889u}, /* MAITAIKHU */ 136 {0x0E4Du, 0xF711u, 0xF899u}, /* NIKHAHIT */ 137 {0x0000u, 0x0000u, 0x0000u} 138 }; 139 static const thai_pua_mapping_t RD_mappings[] = { 140 {0x0E0Du, 0xF70Fu, 0xF89Au}, /* YO YING */ 141 {0x0E10u, 0xF700u, 0xF89Eu}, /* THO THAN */ 142 {0x0000u, 0x0000u, 0x0000u} 143 }; 144 145 switch (action) { 146 case NOP: return u; 147 case SD: pua_mappings = SD_mappings; break; 148 case SDL: pua_mappings = SDL_mappings; break; 149 case SL: pua_mappings = SL_mappings; break; 150 case RD: pua_mappings = RD_mappings; break; 151 } 152 for (; pua_mappings->u; pua_mappings++) 153 if (pua_mappings->u == u) 154 { 155 hb_codepoint_t glyph; 156 if (hb_font_get_glyph (font, pua_mappings->win_pua, 0, &glyph)) 157 return pua_mappings->win_pua; 158 if (hb_font_get_glyph (font, pua_mappings->mac_pua, 0, &glyph)) 159 return pua_mappings->mac_pua; 160 break; 161 } 162 return u; 163 } 164 165 166 static const enum thai_above_state_t 167 { /* Cluster above looks like: */ 168 T0, /* ⣤ */ 169 T1, /* ⣼ */ 170 T2, /* ⣾ */ 171 T3, /* ⣿ */ 172 NUM_ABOVE_STATES 173 } thai_above_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] = 174 { 175 T0, /* NC */ 176 T1, /* AC */ 177 T0, /* RC */ 178 T0, /* DC */ 179 T3, /* NOT_CONSONANT */ 180 }; 181 182 static const struct thai_above_state_machine_edge_t { 183 thai_action_t action; 184 thai_above_state_t next_state; 185 } thai_above_state_machine[NUM_ABOVE_STATES][NUM_MARK_TYPES] = 186 { /*AV*/ /*BV*/ /*T*/ 187 /*T0*/ {{NOP,T3}, {NOP,T0}, {SD, T3}}, 188 /*T1*/ {{SL, T2}, {NOP,T1}, {SDL,T2}}, 189 /*T2*/ {{NOP,T3}, {NOP,T2}, {SL, T3}}, 190 /*T3*/ {{NOP,T3}, {NOP,T3}, {NOP,T3}}, 191 }; 192 193 194 static const enum thai_below_state_t 195 { 196 B0, /* No descender */ 197 B1, /* Removable descender */ 198 B2, /* Strict descender */ 199 NUM_BELOW_STATES 200 } thai_below_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] = 201 { 202 B0, /* NC */ 203 B0, /* AC */ 204 B1, /* RC */ 205 B2, /* DC */ 206 B2, /* NOT_CONSONANT */ 207 }; 208 209 static const struct thai_below_state_machine_edge_t { 210 thai_action_t action; 211 thai_below_state_t next_state; 212 } thai_below_state_machine[NUM_BELOW_STATES][NUM_MARK_TYPES] = 213 { /*AV*/ /*BV*/ /*T*/ 214 /*B0*/ {{NOP,B0}, {NOP,B2}, {NOP, B0}}, 215 /*B1*/ {{NOP,B1}, {RD, B2}, {NOP, B1}}, 216 /*B2*/ {{NOP,B2}, {SD, B2}, {NOP, B2}}, 217 }; 218 219 220 static void 221 do_thai_pua_shaping (const hb_ot_shape_plan_t *plan HB_UNUSED, 222 hb_buffer_t *buffer, 223 hb_font_t *font) 224 { 225 #ifdef HB_NO_OT_SHAPER_THAI_FALLBACK 226 return; 227 #endif 228 229 thai_above_state_t above_state = thai_above_start_state[NOT_CONSONANT]; 230 thai_below_state_t below_state = thai_below_start_state[NOT_CONSONANT]; 231 unsigned int base = 0; 232 233 hb_glyph_info_t *info = buffer->info; 234 unsigned int count = buffer->len; 235 for (unsigned int i = 0; i < count; i++) 236 { 237 thai_mark_type_t mt = get_mark_type (info[i].codepoint); 238 239 if (mt == NOT_MARK) { 240 thai_consonant_type_t ct = get_consonant_type (info[i].codepoint); 241 above_state = thai_above_start_state[ct]; 242 below_state = thai_below_start_state[ct]; 243 base = i; 244 continue; 245 } 246 247 const thai_above_state_machine_edge_t &above_edge = thai_above_state_machine[above_state][mt]; 248 const thai_below_state_machine_edge_t &below_edge = thai_below_state_machine[below_state][mt]; 249 above_state = above_edge.next_state; 250 below_state = below_edge.next_state; 251 252 /* At least one of the above/below actions is NOP. */ 253 thai_action_t action = above_edge.action != NOP ? above_edge.action : below_edge.action; 254 255 buffer->unsafe_to_break (base, i); 256 if (action == RD) 257 info[base].codepoint = thai_pua_shape (info[base].codepoint, action, font); 258 else 259 info[i].codepoint = thai_pua_shape (info[i].codepoint, action, font); 260 } 261 } 262 263 264 static void 265 preprocess_text_thai (const hb_ot_shape_plan_t *plan, 266 hb_buffer_t *buffer, 267 hb_font_t *font) 268 { 269 /* This function implements the shaping logic documented here: 270 * 271 * https://linux.thai.net/~thep/th-otf/shaping.html 272 * 273 * The first shaping rule listed there is needed even if the font has Thai 274 * OpenType tables. The rest do fallback positioning based on PUA codepoints. 275 * We implement that only if there exist no Thai GSUB in the font. 276 */ 277 278 /* The following is NOT specified in the MS OT Thai spec, however, it seems 279 * to be what Uniscribe and other engines implement. According to Eric Muller: 280 * 281 * When you have a SARA AM, decompose it in NIKHAHIT + SARA AA, *and* move the 282 * NIKHAHIT backwards over any above-base marks. 283 * 284 * <0E14, 0E4B, 0E33> -> <0E14, 0E4D, 0E4B, 0E32> 285 * 286 * This reordering is legit only when the NIKHAHIT comes from a SARA AM, not 287 * when it's there to start with. The string <0E14, 0E4B, 0E4D> is probably 288 * not what a user wanted, but the rendering is nevertheless nikhahit above 289 * chattawa. 290 * 291 * Same for Lao. 292 * 293 * Note: 294 * 295 * Uniscribe also does some below-marks reordering. Namely, it positions U+0E3A 296 * after U+0E38 and U+0E39. We do that by modifying the ccc for U+0E3A. 297 * See unicode->modified_combining_class (). Lao does NOT have a U+0E3A 298 * equivalent. 299 */ 300 301 302 /* 303 * Here are the characters of significance: 304 * 305 * Thai Lao 306 * SARA AM: U+0E33 U+0EB3 307 * SARA AA: U+0E32 U+0EB2 308 * Nikhahit: U+0E4D U+0ECD 309 * 310 * Testing shows that Uniscribe reorder the following marks: 311 * Thai: <0E31,0E34..0E37, 0E47..0E4E> 312 * Lao: <0EB1,0EB4..0EB7,0EBB,0EC8..0ECD> 313 * 314 * Note how the Lao versions are the same as Thai + 0x80. 315 */ 316 317 /* We only get one script at a time, so a script-agnostic implementation 318 * is adequate here. */ 319 #define IS_SARA_AM(x) (((x) & ~0x0080u) == 0x0E33u) 320 #define NIKHAHIT_FROM_SARA_AM(x) ((x) - 0x0E33u + 0x0E4Du) 321 #define SARA_AA_FROM_SARA_AM(x) ((x) - 1) 322 #define IS_ABOVE_BASE_MARK(x) (hb_in_ranges<hb_codepoint_t> ((x) & ~0x0080u, 0x0E34u, 0x0E37u, 0x0E47u, 0x0E4Eu, 0x0E31u, 0x0E31u, 0x0E3Bu, 0x0E3Bu)) 323 324 buffer->clear_output (); 325 unsigned int count = buffer->len; 326 for (buffer->idx = 0; buffer->idx < count /* No need for: && buffer->successful */;) 327 { 328 hb_codepoint_t u = buffer->cur().codepoint; 329 if (likely (!IS_SARA_AM (u))) 330 { 331 if (unlikely (!buffer->next_glyph ())) break; 332 continue; 333 } 334 335 /* Is SARA AM. Decompose and reorder. */ 336 (void) buffer->output_glyph (NIKHAHIT_FROM_SARA_AM (u)); 337 _hb_glyph_info_set_continuation (&buffer->prev(), buffer); 338 if (unlikely (!buffer->replace_glyph (SARA_AA_FROM_SARA_AM (u)))) break; 339 340 /* Make Nikhahit be recognized as a ccc=0 mark when zeroing widths. */ 341 unsigned int end = buffer->out_len; 342 _hb_glyph_info_set_general_category (&buffer->out_info[end - 2], HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK); 343 344 /* Ok, let's see... */ 345 unsigned int start = end - 2; 346 while (start > 0 && IS_ABOVE_BASE_MARK (buffer->out_info[start - 1].codepoint)) 347 start--; 348 349 if (start + 2 < end) 350 { 351 /* Move Nikhahit (end-2) to the beginning */ 352 buffer->merge_out_clusters (start, end); 353 hb_glyph_info_t t = buffer->out_info[end - 2]; 354 memmove (buffer->out_info + start + 1, 355 buffer->out_info + start, 356 sizeof (buffer->out_info[0]) * (end - start - 2)); 357 buffer->out_info[start] = t; 358 } 359 else 360 { 361 /* Since we decomposed, and NIKHAHIT is combining, merge clusters with the 362 * previous cluster. */ 363 if (start) 364 buffer->merge_out_clusters (start - 1, end); 365 } 366 } 367 buffer->sync (); 368 369 /* If font has Thai GSUB, we are done. */ 370 if (plan->props.script == HB_SCRIPT_THAI && !plan->map.found_script[0]) 371 do_thai_pua_shaping (plan, buffer, font); 372 } 373 374 const hb_ot_shaper_t _hb_ot_shaper_thai = 375 { 376 nullptr, /* collect_features */ 377 nullptr, /* override_features */ 378 nullptr, /* data_create */ 379 nullptr, /* data_destroy */ 380 preprocess_text_thai, 381 nullptr, /* postprocess_glyphs */ 382 nullptr, /* decompose */ 383 nullptr, /* compose */ 384 nullptr, /* setup_masks */ 385 nullptr, /* reorder_marks */ 386 HB_TAG_NONE, /* gpos_tag */ 387 HB_OT_SHAPE_NORMALIZATION_MODE_DEFAULT, 388 HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_GDEF_LATE, 389 false,/* fallback_position */ 390 }; 391 392 393 #endif