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.hh"
28
29 #ifndef HB_NO_OT_SHAPE
30
31 #include "hb-ot-shape-normalize.hh"
32 #include "hb-ot-shaper.hh"
33 #include "hb-ot-shape.hh"
34
35
36 /*
37 * HIGHLEVEL DESIGN:
38 *
39 * This file exports one main function: _hb_ot_shape_normalize().
40 *
41 * This function closely reflects the Unicode Normalization Algorithm,
42 * yet it's different.
43 *
44 * Each shaper specifies whether it prefers decomposed (NFD) or composed (NFC).
45 * The logic however tries to use whatever the font can support.
46 *
47 * In general what happens is that: each grapheme is decomposed in a chain
48 * of 1:2 decompositions, marks reordered, and then recomposed if desired,
49 * so far it's like Unicode Normalization. However, the decomposition and
50 * recomposition only happens if the font supports the resulting characters.
51 *
52 * The goals are:
53 *
54 * - Try to render all canonically equivalent strings similarly. To really
55 * achieve this we have to always do the full decomposition and then
56 * selectively recompose from there. It's kinda too expensive though, so
57 * we skip some cases. For example, if composed is desired, we simply
58 * don't touch 1-character clusters that are supported by the font, even
59 * though their NFC may be different.
60 *
61 * - When a font has a precomposed character for a sequence but the 'ccmp'
62 * feature in the font is not adequate, use the precomposed character
63 * which typically has better mark positioning.
64 *
65 * - When a font does not support a combining mark, but supports it precomposed
66 * with previous base, use that. This needs the itemizer to have this
67 * knowledge too. We need to provide assistance to the itemizer.
68 *
69 * - When a font does not support a character but supports its canonical
70 * decomposition, well, use the decomposition.
71 *
72 * - The shapers can customize the compose and decompose functions to
73 * offload some of their requirements to the normalizer. For example, the
74 * Indic shaper may want to disallow recomposing of two matras.
75 */
76
77
78 static inline void
set_glyph(hb_glyph_info_t & info,hb_font_t * font)79 set_glyph (hb_glyph_info_t &info, hb_font_t *font)
80 {
81 (void) font->get_nominal_glyph (info.codepoint, &info.glyph_index());
82 }
83
84 static inline void
output_char(hb_buffer_t * buffer,hb_codepoint_t unichar,hb_codepoint_t glyph)85 output_char (hb_buffer_t *buffer, hb_codepoint_t unichar, hb_codepoint_t glyph)
86 {
87 /* This is very confusing indeed. */
88 buffer->cur().glyph_index() = glyph;
89 (void) buffer->output_glyph (unichar);
90 _hb_glyph_info_set_unicode_props (&buffer->prev(), buffer);
91 }
92
93 static inline void
next_char(hb_buffer_t * buffer,hb_codepoint_t glyph)94 next_char (hb_buffer_t *buffer, hb_codepoint_t glyph)
95 {
96 buffer->cur().glyph_index() = glyph;
97 (void) buffer->next_glyph ();
98 }
99
100 static inline void
skip_char(hb_buffer_t * buffer)101 skip_char (hb_buffer_t *buffer)
102 {
103 buffer->skip_glyph ();
104 }
105
106 /* Returns 0 if didn't decompose, number of resulting characters otherwise. */
107 static inline unsigned int
decompose(const hb_ot_shape_normalize_context_t * c,bool shortest,hb_codepoint_t ab)108 decompose (const hb_ot_shape_normalize_context_t *c, bool shortest, hb_codepoint_t ab)
109 {
110 hb_codepoint_t a = 0, b = 0, a_glyph = 0, b_glyph = 0;
111 hb_buffer_t * const buffer = c->buffer;
112 hb_font_t * const font = c->font;
113
114 if (!c->decompose (c, ab, &a, &b) ||
115 (b && !font->get_nominal_glyph (b, &b_glyph)))
116 return 0;
117
118 bool has_a = (bool) font->get_nominal_glyph (a, &a_glyph);
119 if (shortest && has_a) {
120 /* Output a and b */
121 output_char (buffer, a, a_glyph);
122 if (likely (b)) {
123 output_char (buffer, b, b_glyph);
124 return 2;
125 }
126 return 1;
127 }
128
129 if (unsigned ret = decompose (c, shortest, a)) {
130 if (b) {
131 output_char (buffer, b, b_glyph);
132 return ret + 1;
133 }
134 return ret;
135 }
136
137 if (has_a) {
138 output_char (buffer, a, a_glyph);
139 if (likely (b)) {
140 output_char (buffer, b, b_glyph);
141 return 2;
142 }
143 return 1;
144 }
145
146 return 0;
147 }
148
149 static inline void
decompose_current_character(const hb_ot_shape_normalize_context_t * c,bool shortest)150 decompose_current_character (const hb_ot_shape_normalize_context_t *c, bool shortest)
151 {
152 hb_buffer_t * const buffer = c->buffer;
153 hb_codepoint_t u = buffer->cur().codepoint;
154 hb_codepoint_t glyph = 0;
155
156 if (shortest && c->font->get_nominal_glyph (u, &glyph, buffer->not_found))
157 {
158 next_char (buffer, glyph);
159 return;
160 }
161
162 if (decompose (c, shortest, u))
163 {
164 skip_char (buffer);
165 return;
166 }
167
168 if (!shortest && c->font->get_nominal_glyph (u, &glyph, buffer->not_found))
169 {
170 next_char (buffer, glyph);
171 return;
172 }
173
174 if (_hb_glyph_info_is_unicode_space (&buffer->cur()))
175 {
176 hb_codepoint_t space_glyph;
177 hb_unicode_funcs_t::space_t space_type = buffer->unicode->space_fallback_type (u);
178 if (space_type != hb_unicode_funcs_t::NOT_SPACE &&
179 (c->font->get_nominal_glyph (0x0020, &space_glyph) || (space_glyph = buffer->invisible)))
180 {
181 _hb_glyph_info_set_unicode_space_fallback_type (&buffer->cur(), space_type);
182 next_char (buffer, space_glyph);
183 buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_SPACE_FALLBACK;
184 return;
185 }
186 }
187
188 if (u == 0x2011u)
189 {
190 /* U+2011 is the only sensible character that is a no-break version of another character
191 * and not a space. The space ones are handled already. Handle this lone one. */
192 hb_codepoint_t other_glyph;
193 if (c->font->get_nominal_glyph (0x2010u, &other_glyph))
194 {
195 next_char (buffer, other_glyph);
196 return;
197 }
198 }
199
200 next_char (buffer, glyph); /* glyph is initialized in earlier branches. */
201 }
202
203 static inline void
handle_variation_selector_cluster(const hb_ot_shape_normalize_context_t * c,unsigned int end,bool short_circuit HB_UNUSED)204 handle_variation_selector_cluster (const hb_ot_shape_normalize_context_t *c,
205 unsigned int end,
206 bool short_circuit HB_UNUSED)
207 {
208 /* Currently if there's a variation-selector we give-up on normalization, it's just too hard. */
209 hb_buffer_t * const buffer = c->buffer;
210 hb_font_t * const font = c->font;
211 for (; buffer->idx < end - 1 && buffer->successful;) {
212 if (unlikely (buffer->unicode->is_variation_selector (buffer->cur(+1).codepoint))) {
213 if (font->get_variation_glyph (buffer->cur().codepoint, buffer->cur(+1).codepoint, &buffer->cur().glyph_index()))
214 {
215 hb_codepoint_t unicode = buffer->cur().codepoint;
216 (void) buffer->replace_glyphs (2, 1, &unicode);
217 }
218 else
219 {
220 /* Just pass on the two characters separately, let GSUB do its magic. */
221 set_glyph (buffer->cur(), font);
222 (void) buffer->next_glyph ();
223
224 buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_VARIATION_SELECTOR_FALLBACK;
225 _hb_glyph_info_set_variation_selector (&buffer->cur(), true);
226 if (buffer->not_found_variation_selector != HB_CODEPOINT_INVALID)
227 _hb_glyph_info_clear_default_ignorable (&buffer->cur());
228
229 set_glyph (buffer->cur(), font);
230 (void) buffer->next_glyph ();
231 }
232 /* Skip any further variation selectors. */
233 while (buffer->idx < end &&
234 buffer->successful &&
235 unlikely (buffer->unicode->is_variation_selector (buffer->cur().codepoint)))
236 {
237 set_glyph (buffer->cur(), font);
238 (void) buffer->next_glyph ();
239 }
240 }
241 else
242 {
243 set_glyph (buffer->cur(), font);
244 (void) buffer->next_glyph ();
245 }
246 }
247 if (likely (buffer->idx < end))
248 {
249 set_glyph (buffer->cur(), font);
250 (void) buffer->next_glyph ();
251 }
252 }
253
254 static inline void
decompose_multi_char_cluster(const hb_ot_shape_normalize_context_t * c,unsigned int end,bool short_circuit)255 decompose_multi_char_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit)
256 {
257 hb_buffer_t * const buffer = c->buffer;
258 for (unsigned int i = buffer->idx; i < end && buffer->successful; i++)
259 if (unlikely (buffer->unicode->is_variation_selector (buffer->info[i].codepoint))) {
260 handle_variation_selector_cluster (c, end, short_circuit);
261 return;
262 }
263
264 while (buffer->idx < end && buffer->successful)
265 decompose_current_character (c, short_circuit);
266 }
267
268
269 static int
compare_combining_class(const hb_glyph_info_t * pa,const hb_glyph_info_t * pb)270 compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb)
271 {
272 unsigned int a = _hb_glyph_info_get_modified_combining_class (pa);
273 unsigned int b = _hb_glyph_info_get_modified_combining_class (pb);
274
275 return a < b ? -1 : a == b ? 0 : +1;
276 }
277
278
279 void
_hb_ot_shape_normalize(const hb_ot_shape_plan_t * plan,hb_buffer_t * buffer,hb_font_t * font)280 _hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,
281 hb_buffer_t *buffer,
282 hb_font_t *font)
283 {
284 if (unlikely (!buffer->len)) return;
285
286 _hb_buffer_assert_unicode_vars (buffer);
287
288 hb_ot_shape_normalization_mode_t mode = plan->shaper->normalization_preference;
289 if (mode == HB_OT_SHAPE_NORMALIZATION_MODE_AUTO)
290 {
291 if (plan->has_gpos_mark)
292 // https://github.com/harfbuzz/harfbuzz/issues/653#issuecomment-423905920
293 //mode = HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED;
294 mode = HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS;
295 else
296 mode = HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS;
297 }
298
299 hb_ot_shape_normalize_context_t c = {
300 plan,
301 buffer,
302 font,
303 buffer->unicode,
304 plan->shaper->decompose ? plan->shaper->decompose : hb_ot_shape_normalize_context_t::decompose_unicode,
305 plan->shaper->compose ? plan->shaper->compose : hb_ot_shape_normalize_context_t::compose_unicode
306 };
307 c.override_decompose_and_compose (plan->shaper->decompose, plan->shaper->compose);
308
309 bool always_short_circuit = mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE;
310 bool might_short_circuit = always_short_circuit ||
311 (mode != HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED &&
312 mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT);
313 unsigned int count;
314
315 /* We do a fairly straightforward yet custom normalization process in three
316 * separate rounds: decompose, reorder, recompose (if desired). Currently
317 * this makes two buffer swaps. We can make it faster by moving the last
318 * two rounds into the inner loop for the first round, but it's more readable
319 * this way. */
320
321
322 /* First round, decompose */
323
324 bool all_simple = true;
325 {
326 buffer->clear_output ();
327 count = buffer->len;
328 buffer->idx = 0;
329 do
330 {
331 unsigned int end;
332 for (end = buffer->idx + 1; end < count; end++)
333 if (_hb_glyph_info_is_unicode_mark (&buffer->info[end]))
334 break;
335
336 if (end < count)
337 end--; /* Leave one base for the marks to cluster with. */
338
339 /* From idx to end are simple clusters. */
340 if (might_short_circuit)
341 {
342 unsigned int done = font->get_nominal_glyphs (end - buffer->idx,
343 &buffer->cur().codepoint,
344 sizeof (buffer->info[0]),
345 &buffer->cur().glyph_index(),
346 sizeof (buffer->info[0]));
347 if (unlikely (!buffer->next_glyphs (done))) break;
348 }
349 while (buffer->idx < end && buffer->successful)
350 decompose_current_character (&c, might_short_circuit);
351
352 if (buffer->idx == count || !buffer->successful)
353 break;
354
355 all_simple = false;
356
357 /* Find all the marks now. */
358 for (end = buffer->idx + 1; end < count; end++)
359 if (!_hb_glyph_info_is_unicode_mark(&buffer->info[end]))
360 break;
361
362 /* idx to end is one non-simple cluster. */
363 decompose_multi_char_cluster (&c, end, always_short_circuit);
364 }
365 while (buffer->idx < count && buffer->successful);
366 buffer->sync ();
367 }
368
369
370 /* Second round, reorder (inplace) */
371
372 if (!all_simple && buffer->message(font, "start reorder"))
373 {
374 count = buffer->len;
375 hb_glyph_info_t *info = buffer->info;
376 for (unsigned int i = 0; i < count; i++)
377 {
378 if (_hb_glyph_info_get_modified_combining_class (&info[i]) == 0)
379 continue;
380
381 unsigned int end;
382 for (end = i + 1; end < count; end++)
383 if (_hb_glyph_info_get_modified_combining_class (&info[end]) == 0)
384 break;
385
386 /* We are going to do a O(n^2). Only do this if the sequence is short. */
387 if (end - i > HB_OT_SHAPE_MAX_COMBINING_MARKS) {
388 i = end;
389 continue;
390 }
391
392 buffer->sort (i, end, compare_combining_class);
393
394 if (plan->shaper->reorder_marks)
395 plan->shaper->reorder_marks (plan, buffer, i, end);
396
397 i = end;
398 }
399 (void) buffer->message(font, "end reorder");
400 }
401 if (buffer->scratch_flags & HB_BUFFER_SCRATCH_FLAG_HAS_CGJ)
402 {
403 /* For all CGJ, check if it prevented any reordering at all.
404 * If it did NOT, then make it skippable.
405 * https://github.com/harfbuzz/harfbuzz/issues/554
406 */
407 unsigned count = buffer->len;
408 hb_glyph_info_t *info = buffer->info;
409 for (unsigned int i = 1; i + 1 < count; i++)
410 if (info[i].codepoint == 0x034Fu/*CGJ*/ &&
411 (info_cc(info[i+1]) == 0 || info_cc(info[i-1]) <= info_cc(info[i+1])))
412 {
413 _hb_glyph_info_unhide (&info[i]);
414 }
415 }
416
417
418 /* Third round, recompose */
419
420 if (!all_simple &&
421 buffer->successful &&
422 (mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS ||
423 mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT))
424 {
425 /* As noted in the comment earlier, we don't try to combine
426 * ccc=0 chars with their previous Starter. */
427
428 buffer->clear_output ();
429 count = buffer->len;
430 unsigned int starter = 0;
431 (void) buffer->next_glyph ();
432 while (buffer->idx < count /* No need for: && buffer->successful */)
433 {
434 hb_codepoint_t composed, glyph;
435 if (/* We don't try to compose a non-mark character with it's preceding starter.
436 * This is both an optimization to avoid trying to compose every two neighboring
437 * glyphs in most scripts AND a desired feature for Hangul. Apparently Hangul
438 * fonts are not designed to mix-and-match pre-composed syllables and Jamo. */
439 _hb_glyph_info_is_unicode_mark(&buffer->cur()))
440 {
441 if (/* If there's anything between the starter and this char, they should have CCC
442 * smaller than this character's. */
443 (starter == buffer->out_len - 1 ||
444 info_cc (buffer->prev()) < info_cc (buffer->cur())) &&
445 /* And compose. */
446 c.compose (&c,
447 buffer->out_info[starter].codepoint,
448 buffer->cur().codepoint,
449 &composed) &&
450 /* And the font has glyph for the composite. */
451 font->get_nominal_glyph (composed, &glyph))
452 {
453 /* Composes. */
454 if (unlikely (!buffer->next_glyph ())) break; /* Copy to out-buffer. */
455 buffer->merge_out_clusters (starter, buffer->out_len);
456 buffer->out_len--; /* Remove the second composable. */
457 /* Modify starter and carry on. */
458 buffer->out_info[starter].codepoint = composed;
459 buffer->out_info[starter].glyph_index() = glyph;
460 _hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer);
461
462 continue;
463 }
464 }
465
466 /* Blocked, or doesn't compose. */
467 if (unlikely (!buffer->next_glyph ())) break;
468
469 if (info_cc (buffer->prev()) == 0)
470 starter = buffer->out_len - 1;
471 }
472 buffer->sync ();
473 }
474 }
475
476
477 #endif
478