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-shape-complex.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 complex 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
77static bool
78decompose_unicode (const hb_ot_shape_normalize_context_t *c,
79 hb_codepoint_t ab,
80 hb_codepoint_t *a,
81 hb_codepoint_t *b)
82{
83 return (bool) c->unicode->decompose (ab, a, b);
84}
85
86static bool
87compose_unicode (const hb_ot_shape_normalize_context_t *c,
88 hb_codepoint_t a,
89 hb_codepoint_t b,
90 hb_codepoint_t *ab)
91{
92 return (bool) c->unicode->compose (a, b, ab);
93}
94
95static inline void
96set_glyph (hb_glyph_info_t &info, hb_font_t *font)
97{
98 (void) font->get_nominal_glyph (info.codepoint, &info.glyph_index());
99}
100
101static inline void
102output_char (hb_buffer_t *buffer, hb_codepoint_t unichar, hb_codepoint_t glyph)
103{
104 buffer->cur().glyph_index() = glyph;
105 buffer->output_glyph (unichar); /* This is very confusing indeed. */
106 _hb_glyph_info_set_unicode_props (&buffer->prev(), buffer);
107}
108
109static inline void
110next_char (hb_buffer_t *buffer, hb_codepoint_t glyph)
111{
112 buffer->cur().glyph_index() = glyph;
113 buffer->next_glyph ();
114}
115
116static inline void
117skip_char (hb_buffer_t *buffer)
118{
119 buffer->skip_glyph ();
120}
121
122/* Returns 0 if didn't decompose, number of resulting characters otherwise. */
123static inline unsigned int
124decompose (const hb_ot_shape_normalize_context_t *c, bool shortest, hb_codepoint_t ab)
125{
126 hb_codepoint_t a = 0, b = 0, a_glyph = 0, b_glyph = 0;
127 hb_buffer_t * const buffer = c->buffer;
128 hb_font_t * const font = c->font;
129
130 if (!c->decompose (c, ab, &a, &b) ||
131 (b && !font->get_nominal_glyph (b, &b_glyph)))
132 return 0;
133
134 bool has_a = (bool) font->get_nominal_glyph (a, &a_glyph);
135 if (shortest && has_a) {
136 /* Output a and b */
137 output_char (buffer, a, a_glyph);
138 if (likely (b)) {
139 output_char (buffer, b, b_glyph);
140 return 2;
141 }
142 return 1;
143 }
144
145 unsigned int ret;
146 if ((ret = decompose (c, shortest, a))) {
147 if (b) {
148 output_char (buffer, b, b_glyph);
149 return ret + 1;
150 }
151 return ret;
152 }
153
154 if (has_a) {
155 output_char (buffer, a, a_glyph);
156 if (likely (b)) {
157 output_char (buffer, b, b_glyph);
158 return 2;
159 }
160 return 1;
161 }
162
163 return 0;
164}
165
166static inline void
167decompose_current_character (const hb_ot_shape_normalize_context_t *c, bool shortest)
168{
169 hb_buffer_t * const buffer = c->buffer;
170 hb_codepoint_t u = buffer->cur().codepoint;
171 hb_codepoint_t glyph = 0;
172
173 if (shortest && c->font->get_nominal_glyph (u, &glyph))
174 {
175 next_char (buffer, glyph);
176 return;
177 }
178
179 if (decompose (c, shortest, u))
180 {
181 skip_char (buffer);
182 return;
183 }
184
185 if (!shortest && c->font->get_nominal_glyph (u, &glyph))
186 {
187 next_char (buffer, glyph);
188 return;
189 }
190
191 if (_hb_glyph_info_is_unicode_space (&buffer->cur()))
192 {
193 hb_codepoint_t space_glyph;
194 hb_unicode_funcs_t::space_t space_type = buffer->unicode->space_fallback_type (u);
195 if (space_type != hb_unicode_funcs_t::NOT_SPACE && c->font->get_nominal_glyph (0x0020u, &space_glyph))
196 {
197 _hb_glyph_info_set_unicode_space_fallback_type (&buffer->cur(), space_type);
198 next_char (buffer, space_glyph);
199 buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_SPACE_FALLBACK;
200 return;
201 }
202 }
203
204 if (u == 0x2011u)
205 {
206 /* U+2011 is the only sensible character that is a no-break version of another character
207 * and not a space. The space ones are handled already. Handle this lone one. */
208 hb_codepoint_t other_glyph;
209 if (c->font->get_nominal_glyph (0x2010u, &other_glyph))
210 {
211 next_char (buffer, other_glyph);
212 return;
213 }
214 }
215
216 next_char (buffer, glyph); /* glyph is initialized in earlier branches. */
217}
218
219static inline void
220handle_variation_selector_cluster (const hb_ot_shape_normalize_context_t *c,
221 unsigned int end,
222 bool short_circuit HB_UNUSED)
223{
224 /* TODO Currently if there's a variation-selector we give-up, it's just too hard. */
225 hb_buffer_t * const buffer = c->buffer;
226 hb_font_t * const font = c->font;
227 for (; buffer->idx < end - 1 && buffer->successful;) {
228 if (unlikely (buffer->unicode->is_variation_selector (buffer->cur(+1).codepoint))) {
229 if (font->get_variation_glyph (buffer->cur().codepoint, buffer->cur(+1).codepoint, &buffer->cur().glyph_index()))
230 {
231 hb_codepoint_t unicode = buffer->cur().codepoint;
232 buffer->replace_glyphs (2, 1, &unicode);
233 }
234 else
235 {
236 /* Just pass on the two characters separately, let GSUB do its magic. */
237 set_glyph (buffer->cur(), font);
238 buffer->next_glyph ();
239 set_glyph (buffer->cur(), font);
240 buffer->next_glyph ();
241 }
242 /* Skip any further variation selectors. */
243 while (buffer->idx < end && unlikely (buffer->unicode->is_variation_selector (buffer->cur().codepoint)))
244 {
245 set_glyph (buffer->cur(), font);
246 buffer->next_glyph ();
247 }
248 } else {
249 set_glyph (buffer->cur(), font);
250 buffer->next_glyph ();
251 }
252 }
253 if (likely (buffer->idx < end)) {
254 set_glyph (buffer->cur(), font);
255 buffer->next_glyph ();
256 }
257}
258
259static inline void
260decompose_multi_char_cluster (const hb_ot_shape_normalize_context_t *c, unsigned int end, bool short_circuit)
261{
262 hb_buffer_t * const buffer = c->buffer;
263 for (unsigned int i = buffer->idx; i < end && buffer->successful; i++)
264 if (unlikely (buffer->unicode->is_variation_selector (buffer->info[i].codepoint))) {
265 handle_variation_selector_cluster (c, end, short_circuit);
266 return;
267 }
268
269 while (buffer->idx < end && buffer->successful)
270 decompose_current_character (c, short_circuit);
271}
272
273
274static int
275compare_combining_class (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb)
276{
277 unsigned int a = _hb_glyph_info_get_modified_combining_class (pa);
278 unsigned int b = _hb_glyph_info_get_modified_combining_class (pb);
279
280 return a < b ? -1 : a == b ? 0 : +1;
281}
282
283
284void
285_hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,
286 hb_buffer_t *buffer,
287 hb_font_t *font)
288{
289 if (unlikely (!buffer->len)) return;
290
291 _hb_buffer_assert_unicode_vars (buffer);
292
293 hb_ot_shape_normalization_mode_t mode = plan->shaper->normalization_preference;
294 if (mode == HB_OT_SHAPE_NORMALIZATION_MODE_AUTO)
295 {
296 if (plan->has_gpos_mark)
297 // https://github.com/harfbuzz/harfbuzz/issues/653#issuecomment-423905920
298 //mode = HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED;
299 mode = HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS;
300 else
301 mode = HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS;
302 }
303
304 const hb_ot_shape_normalize_context_t c = {
305 plan,
306 buffer,
307 font,
308 buffer->unicode,
309 plan->shaper->decompose ? plan->shaper->decompose : decompose_unicode,
310 plan->shaper->compose ? plan->shaper->compose : compose_unicode
311 };
312
313 bool always_short_circuit = mode == HB_OT_SHAPE_NORMALIZATION_MODE_NONE;
314 bool might_short_circuit = always_short_circuit ||
315 (mode != HB_OT_SHAPE_NORMALIZATION_MODE_DECOMPOSED &&
316 mode != HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT);
317 unsigned int count;
318
319 /* We do a fairly straightforward yet custom normalization process in three
320 * separate rounds: decompose, reorder, recompose (if desired). Currently
321 * this makes two buffer swaps. We can make it faster by moving the last
322 * two rounds into the inner loop for the first round, but it's more readable
323 * this way. */
324
325
326 /* First round, decompose */
327
328 bool all_simple = true;
329 {
330 buffer->clear_output ();
331 count = buffer->len;
332 buffer->idx = 0;
333 do
334 {
335 unsigned int end;
336 for (end = buffer->idx + 1; end < count; end++)
337 if (unlikely (HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->info[end]))))
338 break;
339
340 if (end < count)
341 end--; /* Leave one base for the marks to cluster with. */
342
343 /* From idx to end are simple clusters. */
344 if (might_short_circuit)
345 {
346 unsigned int done = font->get_nominal_glyphs (end - buffer->idx,
347 &buffer->cur().codepoint,
348 sizeof (buffer->info[0]),
349 &buffer->cur().glyph_index(),
350 sizeof (buffer->info[0]));
351 buffer->next_glyphs (done);
352 }
353 while (buffer->idx < end && buffer->successful)
354 decompose_current_character (&c, might_short_circuit);
355
356 if (buffer->idx == count || !buffer->successful)
357 break;
358
359 all_simple = false;
360
361 /* Find all the marks now. */
362 for (end = buffer->idx + 1; end < count; end++)
363 if (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->info[end])))
364 break;
365
366 /* idx to end is one non-simple cluster. */
367 decompose_multi_char_cluster (&c, end, always_short_circuit);
368 }
369 while (buffer->idx < count && buffer->successful);
370 buffer->swap_buffers ();
371 }
372
373
374 /* Second round, reorder (inplace) */
375
376 if (!all_simple)
377 {
378 count = buffer->len;
379 for (unsigned int i = 0; i < count; i++)
380 {
381 if (_hb_glyph_info_get_modified_combining_class (&buffer->info[i]) == 0)
382 continue;
383
384 unsigned int end;
385 for (end = i + 1; end < count; end++)
386 if (_hb_glyph_info_get_modified_combining_class (&buffer->info[end]) == 0)
387 break;
388
389 /* We are going to do a O(n^2). Only do this if the sequence is short. */
390 if (end - i > HB_OT_SHAPE_COMPLEX_MAX_COMBINING_MARKS) {
391 i = end;
392 continue;
393 }
394
395 buffer->sort (i, end, compare_combining_class);
396
397 if (plan->shaper->reorder_marks)
398 plan->shaper->reorder_marks (plan, buffer, i, end);
399
400 i = end;
401 }
402 }
403 if (buffer->scratch_flags & HB_BUFFER_SCRATCH_FLAG_HAS_CGJ)
404 {
405 /* For all CGJ, check if it prevented any reordering at all.
406 * If it did NOT, then make it skippable.
407 * https://github.com/harfbuzz/harfbuzz/issues/554
408 */
409 for (unsigned int i = 1; i + 1 < buffer->len; i++)
410 if (buffer->info[i].codepoint == 0x034Fu/*CGJ*/ &&
411 info_cc(buffer->info[i-1]) <= info_cc(buffer->info[i+1]))
412 {
413 _hb_glyph_info_unhide (&buffer->info[i]);
414 }
415 }
416
417
418 /* Third round, recompose */
419
420 if (!all_simple &&
421 (mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS ||
422 mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT))
423 {
424 /* As noted in the comment earlier, we don't try to combine
425 * ccc=0 chars with their previous Starter. */
426
427 buffer->clear_output ();
428 count = buffer->len;
429 unsigned int starter = 0;
430 buffer->next_glyph ();
431 while (buffer->idx < count && buffer->successful)
432 {
433 hb_codepoint_t composed, glyph;
434 if (/* We don't try to compose a non-mark character with it's preceding starter.
435 * This is both an optimization to avoid trying to compose every two neighboring
436 * glyphs in most scripts AND a desired feature for Hangul. Apparently Hangul
437 * fonts are not designed to mix-and-match pre-composed syllables and Jamo. */
438 HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->cur())))
439 {
440 if (/* If there's anything between the starter and this char, they should have CCC
441 * smaller than this character's. */
442 (starter == buffer->out_len - 1 ||
443 info_cc (buffer->prev()) < info_cc (buffer->cur())) &&
444 /* And compose. */
445 c.compose (&c,
446 buffer->out_info[starter].codepoint,
447 buffer->cur().codepoint,
448 &composed) &&
449 /* And the font has glyph for the composite. */
450 font->get_nominal_glyph (composed, &glyph))
451 {
452 /* Composes. */
453 buffer->next_glyph (); /* Copy to out-buffer. */
454 if (unlikely (!buffer->successful))
455 return;
456 buffer->merge_out_clusters (starter, buffer->out_len);
457 buffer->out_len--; /* Remove the second composable. */
458 /* Modify starter and carry on. */
459 buffer->out_info[starter].codepoint = composed;
460 buffer->out_info[starter].glyph_index() = glyph;
461 _hb_glyph_info_set_unicode_props (&buffer->out_info[starter], buffer);
462
463 continue;
464 }
465 }
466
467 /* Blocked, or doesn't compose. */
468 buffer->next_glyph ();
469
470 if (info_cc (buffer->prev()) == 0)
471 starter = buffer->out_len - 1;
472 }
473 buffer->swap_buffers ();
474 }
475}
476
477
478#endif
479