1 /* 2 * Copyright 2011,2012 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-ot-shape-normalize-private.hh" 28 #include "hb-ot-shape-complex-private.hh" 29 #include "hb-ot-shape-private.hh" 30 31 32 /* 33 * HIGHLEVEL DESIGN: 34 * 35 * This file exports one main function: _hb_ot_shape_normalize(). 36 * 37 * This function closely reflects the Unicode Normalization Algorithm, 38 * yet it's different. 39 * 40 * Each shaper specifies whether it prefers decomposed (NFD) or composed (NFC). 41 * The logic however tries to use whatever the font can support. 42 * 43 * In general what happens is that: each grapheme is decomposed in a chain 44 * of 1:2 decompositions, marks reordered, and then recomposed if desired, 45 * so far it's like Unicode Normalization. However, the decomposition and 46 * recomposition only happens if the font supports the resulting characters. 47 * 48 * The goals are: 49 * 50 * - Try to render all canonically equivalent strings similarly. To really 51 * achieve this we have to always do the full decomposition and then 52 * selectively recompose from there. It's kinda too expensive though, so 53 * we skip some cases. For example, if composed is desired, we simply 54 * don't touch 1-character clusters that are supported by the font, even 55 * though their NFC may be different. 56 * 57 * - When a font has a precomposed character for a sequence but the 'ccmp' 58 * feature in the font is not adequate, use the precomposed character 59 * which typically has better mark positioning. 60 * 61 * - When a font does not support a combining mark, but supports it precomposed 62 * with previous base, use that. This needs the itemizer to have this 63 * knowledge too. We need to provide assistance to the itemizer. 64 * 65 * - When a font does not support a character but supports its canonical 66 * decomposition, well, use the decomposition. 67 * 68 * - The complex shapers can customize the compose and decompose functions to 69 * offload some of their requirements to the normalizer. For example, the 70 * Indic shaper may want to disallow recomposing of two matras. 71 */ 72 73 static bool 74 decompose_unicode (const hb_ot_shape_normalize_context_t *c, 75 hb_codepoint_t ab, 76 hb_codepoint_t *a, 77 hb_codepoint_t *b) 78 { 79 return (bool) c->unicode->decompose (ab, a, b); 80 } 81 82 static bool 83 compose_unicode (const hb_ot_shape_normalize_context_t *c, 84 hb_codepoint_t a, 85 hb_codepoint_t b, 86 hb_codepoint_t *ab) 87 { 88 return (bool) c->unicode->compose (a, b, ab); 89 } 90 91 static inline void 92 set_glyph (hb_glyph_info_t &info, hb_font_t *font) 93 { 94 (void) font->get_nominal_glyph (info.codepoint, &info.glyph_index()); 95 } 96 97 static inline void 98 output_char (hb_buffer_t *buffer, hb_codepoint_t unichar, hb_codepoint_t glyph) 99 { 100 buffer->cur().glyph_index() = glyph; 101 buffer->output_glyph (unichar); /* This is very confusing indeed. */ 102 _hb_glyph_info_set_unicode_props (&buffer->prev(), buffer); 103 } 104 105 static inline void 106 next_char (hb_buffer_t *buffer, hb_codepoint_t glyph) 107 { 108 buffer->cur().glyph_index() = glyph; 109 buffer->next_glyph (); 110 } 111 112 static inline void 113 skip_char (hb_buffer_t *buffer) 114 { 115 buffer->skip_glyph (); 116 } 117 118 /* Returns 0 if didn't decompose, number of resulting characters otherwise. */ 119 static inline unsigned int 120 decompose (const hb_ot_shape_normalize_context_t *c, bool shortest, hb_codepoint_t ab) 121 { 122 hb_codepoint_t a, b, a_glyph, b_glyph; 123 hb_buffer_t * const buffer = c->buffer; 124 hb_font_t * const font = c->font; 125 126 if (!c->decompose (c, ab, &a, &b) || 127 (b && !font->get_nominal_glyph (b, &b_glyph))) 128 return 0; 129 130 bool has_a = (bool) font->get_nominal_glyph (a, &a_glyph); 131 if (shortest && has_a) { 132 /* Output a and b */ 133 output_char (buffer, a, a_glyph); 134 if (likely (b)) { 135 output_char (buffer, b, b_glyph); 136 return 2; 137 } 138 return 1; 139 } 140 141 unsigned int ret; 142 if ((ret = decompose (c, shortest, a))) { 143 if (b) { 144 output_char (buffer, b, b_glyph); 145 return ret + 1; 146 } 147 return ret; 148 } 149 150 if (has_a) { 151 output_char (buffer, a, a_glyph); 152 if (likely (b)) { 153 output_char (buffer, b, b_glyph); 154 return 2; 155 } 156 return 1; 157 } 158 159 return 0; 160 } 161 162 static inline void 163 decompose_current_character (const hb_ot_shape_normalize_context_t *c, bool shortest) 164 { 165 hb_buffer_t * const buffer = c->buffer; 166 hb_codepoint_t u = buffer->cur().codepoint; 167 hb_codepoint_t glyph; 168 169 if (shortest && c->font->get_nominal_glyph (u, &glyph)) 170 { 171 next_char (buffer, glyph); 172 return; 173 } 174 175 if (decompose (c, shortest, u)) 176 { 177 skip_char (buffer); 178 return; 179 } 180 181 if (!shortest && c->font->get_nominal_glyph (u, &glyph)) 182 { 183 next_char (buffer, glyph); 184 return; 185 } 186 187 if (_hb_glyph_info_is_unicode_space (&buffer->cur())) 188 { 189 hb_codepoint_t space_glyph; 190 hb_unicode_funcs_t::space_t space_type = buffer->unicode->space_fallback_type (u); 191 if (space_type != hb_unicode_funcs_t::NOT_SPACE && c->font->get_nominal_glyph (0x0020u, &space_glyph)) 192 { 193 _hb_glyph_info_set_unicode_space_fallback_type (&buffer->cur(), space_type); 194 next_char (buffer, space_glyph); 195 buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_SPACE_FALLBACK; 196 return; 197 } 198 } 199 200 if (u == 0x2011u) 201 { 202 /* U+2011 is the only sensible character that is a no-break version of another character 203 * and not a space. The space ones are handled already. Handle this lone one. */ 204 hb_codepoint_t other_glyph; 205 if (c->font->get_nominal_glyph (0x2010u, &other_glyph)) 206 { 207 next_char (buffer, other_glyph); 208 return; 209 } 210 } 211 212 next_char (buffer, glyph); /* glyph is initialized in earlier branches. */ 213 } 214 215 static inline void 216 handle_variation_selector_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit) 217 { 218 /* TODO Currently if there's a variation-selector we give-up, it's just too hard. */ 219 hb_buffer_t * const buffer = c->buffer; 220 hb_font_t * const font = c->font; 221 for (; buffer->idx < end - 1 && !buffer->in_error;) { 222 if (unlikely (buffer->unicode->is_variation_selector (buffer->cur(+1).codepoint))) { 223 /* The next two lines are some ugly lines... But work. */ 224 if (font->get_variation_glyph (buffer->cur().codepoint, buffer->cur(+1).codepoint, &buffer->cur().glyph_index())) 225 { 226 buffer->replace_glyphs (2, 1, &buffer->cur().codepoint); 227 } 228 else 229 { 230 /* Just pass on the two characters separately, let GSUB do its magic. */ 231 set_glyph (buffer->cur(), font); 232 buffer->next_glyph (); 233 set_glyph (buffer->cur(), font); 234 buffer->next_glyph (); 235 } 236 /* Skip any further variation selectors. */ 237 while (buffer->idx < end && unlikely (buffer->unicode->is_variation_selector (buffer->cur().codepoint))) 238 { 239 set_glyph (buffer->cur(), font); 240 buffer->next_glyph (); 241 } 242 } else { 243 set_glyph (buffer->cur(), font); 244 buffer->next_glyph (); 245 } 246 } 247 if (likely (buffer->idx < end)) { 248 set_glyph (buffer->cur(), font); 249 buffer->next_glyph (); 250 } 251 } 252 253 static inline void 254 decompose_multi_char_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit) 255 { 256 hb_buffer_t * const buffer = c->buffer; 257 for (unsigned int i = buffer->idx; i < end && !buffer->in_error; i++) 258 if (unlikely (buffer->unicode->is_variation_selector (buffer->info[i].codepoint))) { 259 handle_variation_selector_cluster (c, end, short_circuit); 260 return; 261 } 262 263 while (buffer->idx < end && !buffer->in_error) 264 decompose_current_character (c, short_circuit); 265 } 266 267 static inline void 268 decompose_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool might_short_circuit, bool always_short_circuit) 269 { 270 if (likely (c->buffer->idx + 1 == end)) 271 decompose_current_character (c, might_short_circuit); 272 else 273 decompose_multi_char_cluster (c, end, always_short_circuit); 274 } 275 276 277 static int 278 compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb) 279 { 280 unsigned int a = _hb_glyph_info_get_modified_combining_class (pa); 281 unsigned int b = _hb_glyph_info_get_modified_combining_class (pb); 282 283 return a < b ? -1 : a == b ? 0 : +1; 284 } 285 286 287 void 288 _hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan, 289 hb_buffer_t *buffer, 290 hb_font_t *font) 291 { 292 if (unlikely (!buffer->len)) return; 293 294 _hb_buffer_assert_unicode_vars (buffer); 295 296 hb_ot_shape_normalization_mode_t mode = plan->shaper->normalization_preference; 297 const hb_ot_shape_normalize_context_t c = { 298 plan, 299 buffer, 300 font, 301 buffer->unicode, 302 plan->shaper->decompose ? plan->shaper->decompose : decompose_unicode, 303 plan->shaper->compose ? plan->shaper->compose : compose_unicode 304 }; 305 306 bool always_short_circuit = mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE; 307 bool might_short_circuit = always_short_circuit || 308 (mode != HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED && 309 mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT); 310 unsigned int count; 311 312 /* We do a fairly straightforward yet custom normalization process in three 313 * separate rounds: decompose, reorder, recompose (if desired). Currently 314 * this makes two buffer swaps. We can make it faster by moving the last 315 * two rounds into the inner loop for the first round, but it's more readable 316 * this way. */ 317 318 319 /* First round, decompose */ 320 321 buffer->clear_output (); 322 count = buffer->len; 323 for (buffer->idx = 0; buffer->idx < count && !buffer->in_error;) 324 { 325 unsigned int end; 326 for (end = buffer->idx + 1; end < count; end++) 327 if (likely (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->info[end])))) 328 break; 329 330 decompose_cluster (&c, end, might_short_circuit, always_short_circuit); 331 } 332 buffer->swap_buffers (); 333 334 335 /* Second round, reorder (inplace) */ 336 337 count = buffer->len; 338 for (unsigned int i = 0; i < count; i++) 339 { 340 if (_hb_glyph_info_get_modified_combining_class (&buffer->info[i]) == 0) 341 continue; 342 343 unsigned int end; 344 for (end = i + 1; end < count; end++) 345 if (_hb_glyph_info_get_modified_combining_class (&buffer->info[end]) == 0) 346 break; 347 348 /* We are going to do a O(n^2). Only do this if the sequence is short, 349 * but not too short ;). */ 350 if (end - i < 2 || end - i > HB_OT_SHAPE_COMPLEX_MAX_COMBINING_MARKS) { 351 i = end; 352 continue; 353 } 354 355 buffer->sort (i, end, compare_combining_class); 356 357 if (plan->shaper->reorder_marks) 358 plan->shaper->reorder_marks (plan, buffer, i, end); 359 360 i = end; 361 } 362 363 364 if (mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE || 365 mode == HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED) 366 return; 367 368 /* Third round, recompose */ 369 370 /* As noted in the comment earlier, we don't try to combine 371 * ccc=0 chars with their previous Starter. */ 372 373 buffer->clear_output (); 374 count = buffer->len; 375 unsigned int starter = 0; 376 bool combine = true; 377 buffer->next_glyph (); 378 while (buffer->idx < count && !buffer->in_error) 379 { 380 hb_codepoint_t composed, glyph; 381 if (combine && 382 /* We don't try to compose a non-mark character with it's preceding starter. 383 * This is both an optimization to avoid trying to compose every two neighboring 384 * glyphs in most scripts AND a desired feature for Hangul. Apparently Hangul 385 * fonts are not designed to mix-and-match pre-composed syllables and Jamo. */ 386 HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->cur()))) 387 { 388 if (/* If there's anything between the starter and this char, they should have CCC 389 * smaller than this character's. */ 390 (starter == buffer->out_len - 1 || 391 info_cc (buffer->prev()) < info_cc (buffer->cur())) && 392 /* And compose. */ 393 c.compose (&c, 394 buffer->out_info[starter].codepoint, 395 buffer->cur().codepoint, 396 &composed) && 397 /* And the font has glyph for the composite. */ 398 font->get_nominal_glyph (composed, &glyph)) 399 { 400 /* Composes. */ 401 buffer->next_glyph (); /* Copy to out-buffer. */ 402 if (unlikely (buffer->in_error)) 403 return; 404 buffer->merge_out_clusters (starter, buffer->out_len); 405 buffer->out_len--; /* Remove the second composable. */ 406 /* Modify starter and carry on. */ 407 buffer->out_info[starter].codepoint = composed; 408 buffer->out_info[starter].glyph_index() = glyph; 409 _hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer); 410 411 continue; 412 } 413 else if (/* We sometimes custom-tailor the sorted order of marks. In that case, stop 414 * trying to combine as soon as combining-class drops. */ 415 starter < buffer->out_len - 1 && 416 info_cc (buffer->prev()) > info_cc (buffer->cur())) 417 combine = false; 418 } 419 420 /* Blocked, or doesn't compose. */ 421 buffer->next_glyph (); 422 423 if (info_cc (buffer->prev()) == 0) 424 { 425 starter = buffer->out_len - 1; 426 combine = true; 427 } 428 } 429 buffer->swap_buffers (); 430 431 } 432
