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comparison mupdf-source/thirdparty/harfbuzz/src/hb-subset.cc @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1:1d09e1dec1d9 2:b50eed0cc0ef
1 /*
2 * Copyright © 2018 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): Garret Rieger, Rod Sheeter, Behdad Esfahbod
25 */
26
27 #include "hb.hh"
28 #include "hb-open-type.hh"
29
30 #include "hb-subset.hh"
31
32 #include "hb-open-file.hh"
33 #include "hb-ot-cmap-table.hh"
34 #include "hb-ot-glyf-table.hh"
35 #include "hb-ot-hdmx-table.hh"
36 #include "hb-ot-head-table.hh"
37 #include "hb-ot-hhea-table.hh"
38 #include "hb-ot-hmtx-table.hh"
39 #include "hb-ot-maxp-table.hh"
40 #include "hb-ot-color-sbix-table.hh"
41 #include "hb-ot-color-colr-table.hh"
42 #include "hb-ot-color-cpal-table.hh"
43 #include "hb-ot-os2-table.hh"
44 #include "hb-ot-post-table.hh"
45 #include "hb-ot-post-table-v2subset.hh"
46 #include "hb-ot-cff1-table.hh"
47 #include "hb-ot-cff2-table.hh"
48 #include "hb-ot-vorg-table.hh"
49 #include "hb-ot-name-table.hh"
50 #include "hb-ot-color-cbdt-table.hh"
51 #include "hb-ot-layout-gsub-table.hh"
52 #include "hb-ot-layout-gpos-table.hh"
53 #include "hb-ot-var-fvar-table.hh"
54 #include "hb-ot-var-gvar-table.hh"
55 #include "hb-ot-var-hvar-table.hh"
56 #include "hb-ot-math-table.hh"
57 #include "hb-ot-stat-table.hh"
58 #include "hb-repacker.hh"
59 #include "hb-subset-accelerator.hh"
60
61 using OT::Layout::GSUB;
62 using OT::Layout::GPOS;
63
64 /**
65 * SECTION:hb-subset
66 * @title: hb-subset
67 * @short_description: Subsets font files.
68 * @include: hb-subset.h
69 *
70 * Subsetting reduces the codepoint coverage of font files and removes all data
71 * that is no longer needed. A subset input describes the desired subset. The input is
72 * provided along with a font to the subsetting operation. Output is a new font file
73 * containing only the data specified in the input.
74 *
75 * Currently most outline and bitmap tables are supported: glyf, CFF, CFF2, sbix,
76 * COLR, and CBDT/CBLC. This also includes fonts with variable outlines via OpenType
77 * variations. Notably EBDT/EBLC and SVG are not supported. Layout subsetting is supported
78 * only for OpenType Layout tables (GSUB, GPOS, GDEF). Notably subsetting of graphite or AAT tables
79 * is not yet supported.
80 *
81 * Fonts with graphite or AAT tables may still be subsetted but will likely need to use the
82 * retain glyph ids option and configure the subset to pass through the layout tables untouched.
83 */
84
85
86 hb_user_data_key_t _hb_subset_accelerator_user_data_key = {};
87
88
89 /*
90 * The list of tables in the open type spec. Used to check for tables that may need handling
91 * if we are unable to list the tables in a face.
92 */
93 static hb_tag_t known_tables[] {
94 HB_TAG ('a', 'v', 'a', 'r'),
95 HB_OT_TAG_BASE,
96 HB_OT_TAG_CBDT,
97 HB_OT_TAG_CBLC,
98 HB_OT_TAG_cff1,
99 HB_OT_TAG_cff2,
100 HB_OT_TAG_cmap,
101 HB_OT_TAG_COLR,
102 HB_OT_TAG_CPAL,
103 HB_TAG ('c', 'v', 'a', 'r'),
104 HB_TAG ('c', 'v', 't', ' '),
105 HB_TAG ('D', 'S', 'I', 'G'),
106 HB_TAG ('E', 'B', 'D', 'T'),
107 HB_TAG ('E', 'B', 'L', 'C'),
108 HB_TAG ('E', 'B', 'S', 'C'),
109 HB_TAG ('f', 'p', 'g', 'm'),
110 HB_TAG ('f', 'v', 'a', 'r'),
111 HB_TAG ('g', 'a', 's', 'p'),
112 HB_OT_TAG_GDEF,
113 HB_OT_TAG_glyf,
114 HB_OT_TAG_GPOS,
115 HB_OT_TAG_GSUB,
116 HB_OT_TAG_gvar,
117 HB_OT_TAG_hdmx,
118 HB_OT_TAG_head,
119 HB_OT_TAG_hhea,
120 HB_OT_TAG_hmtx,
121 HB_OT_TAG_HVAR,
122 HB_OT_TAG_JSTF,
123 HB_TAG ('k', 'e', 'r', 'n'),
124 HB_OT_TAG_loca,
125 HB_TAG ('L', 'T', 'S', 'H'),
126 HB_OT_TAG_MATH,
127 HB_OT_TAG_maxp,
128 HB_TAG ('M', 'E', 'R', 'G'),
129 HB_TAG ('m', 'e', 't', 'a'),
130 HB_TAG ('M', 'V', 'A', 'R'),
131 HB_TAG ('P', 'C', 'L', 'T'),
132 HB_OT_TAG_post,
133 HB_TAG ('p', 'r', 'e', 'p'),
134 HB_OT_TAG_sbix,
135 HB_TAG ('S', 'T', 'A', 'T'),
136 HB_TAG ('S', 'V', 'G', ' '),
137 HB_TAG ('V', 'D', 'M', 'X'),
138 HB_OT_TAG_vhea,
139 HB_OT_TAG_vmtx,
140 HB_OT_TAG_VORG,
141 HB_OT_TAG_VVAR,
142 HB_OT_TAG_name,
143 HB_OT_TAG_OS2
144 };
145
146 static bool _table_is_empty (const hb_face_t *face, hb_tag_t tag)
147 {
148 hb_blob_t* blob = hb_face_reference_table (face, tag);
149 bool result = (blob == hb_blob_get_empty ());
150 hb_blob_destroy (blob);
151 return result;
152 }
153
154 static unsigned int
155 _get_table_tags (const hb_subset_plan_t* plan,
156 unsigned int start_offset,
157 unsigned int *table_count, /* IN/OUT */
158 hb_tag_t *table_tags /* OUT */)
159 {
160 unsigned num_tables = hb_face_get_table_tags (plan->source, 0, nullptr, nullptr);
161 if (num_tables)
162 return hb_face_get_table_tags (plan->source, start_offset, table_count, table_tags);
163
164 // If face has 0 tables associated with it, assume that it was built from
165 // hb_face_create_tables and thus is unable to list its tables. Fallback to
166 // checking each table type we can handle for existence instead.
167 auto it =
168 hb_concat (
169 + hb_array (known_tables)
170 | hb_filter ([&] (hb_tag_t tag) {
171 return !_table_is_empty (plan->source, tag) && !plan->no_subset_tables->has (tag);
172 })
173 | hb_map ([] (hb_tag_t tag) -> hb_tag_t { return tag; }),
174
175 plan->no_subset_tables->iter ()
176 | hb_filter([&] (hb_tag_t tag) {
177 return !_table_is_empty (plan->source, tag);
178 }));
179
180 it += start_offset;
181
182 unsigned num_written = 0;
183 while (bool (it) && num_written < *table_count)
184 table_tags[num_written++] = *it++;
185
186 *table_count = num_written;
187 return num_written;
188 }
189
190
191 static unsigned
192 _plan_estimate_subset_table_size (hb_subset_plan_t *plan,
193 unsigned table_len,
194 bool same_size)
195 {
196 unsigned src_glyphs = plan->source->get_num_glyphs ();
197 unsigned dst_glyphs = plan->glyphset ()->get_population ();
198
199 if (unlikely (!src_glyphs) || same_size)
200 return 512 + table_len;
201
202 return 512 + (unsigned) (table_len * sqrt ((double) dst_glyphs / src_glyphs));
203 }
204
205 /*
206 * Repack the serialization buffer if any offset overflows exist.
207 */
208 static hb_blob_t*
209 _repack (hb_tag_t tag, const hb_serialize_context_t& c)
210 {
211 if (tag != HB_OT_TAG_GPOS
212 && tag != HB_OT_TAG_GSUB)
213 {
214 // Check for overflow in a non-handled table.
215 return c.successful () ? c.copy_blob () : nullptr;
216 }
217
218 if (!c.offset_overflow ())
219 return c.copy_blob ();
220
221 hb_blob_t* result = hb_resolve_overflows (c.object_graph (), tag);
222
223 if (unlikely (!result))
224 {
225 DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c offset overflow resolution failed.",
226 HB_UNTAG (tag));
227 return nullptr;
228 }
229
230 return result;
231 }
232
233 template<typename TableType>
234 static
235 bool
236 _try_subset (const TableType *table,
237 hb_vector_t<char>* buf,
238 hb_subset_context_t* c /* OUT */)
239 {
240 c->serializer->start_serialize<TableType> ();
241 if (c->serializer->in_error ()) return false;
242
243 bool needed = table->subset (c);
244 if (!c->serializer->ran_out_of_room ())
245 {
246 c->serializer->end_serialize ();
247 return needed;
248 }
249
250 unsigned buf_size = buf->allocated;
251 buf_size = buf_size * 2 + 16;
252
253
254
255
256 DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c ran out of room; reallocating to %u bytes.",
257 HB_UNTAG (c->table_tag), buf_size);
258
259 if (unlikely (buf_size > c->source_blob->length * 16 ||
260 !buf->alloc (buf_size)))
261 {
262 DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c failed to reallocate %u bytes.",
263 HB_UNTAG (c->table_tag), buf_size);
264 return needed;
265 }
266
267 c->serializer->reset (buf->arrayZ, buf->allocated);
268 return _try_subset (table, buf, c);
269 }
270
271 template<typename TableType>
272 static bool
273 _subset (hb_subset_plan_t *plan, hb_vector_t<char> &buf)
274 {
275 hb_blob_ptr_t<TableType> source_blob = plan->source_table<TableType> ();
276 const TableType *table = source_blob.get ();
277
278 hb_tag_t tag = TableType::tableTag;
279 if (!source_blob.get_blob()->data)
280 {
281 DEBUG_MSG (SUBSET, nullptr,
282 "OT::%c%c%c%c::subset sanitize failed on source table.", HB_UNTAG (tag));
283 source_blob.destroy ();
284 return false;
285 }
286
287 /* Tables that we want to allocate same space as the source table. For GSUB/GPOS it's
288 * because those are expensive to subset, so giving them more room is fine. */
289 bool same_size_table = TableType::tableTag == HB_OT_TAG_GSUB ||
290 TableType::tableTag == HB_OT_TAG_GPOS ||
291 TableType::tableTag == HB_OT_TAG_name;
292
293 unsigned buf_size = _plan_estimate_subset_table_size (plan, source_blob.get_length (), same_size_table);
294 DEBUG_MSG (SUBSET, nullptr,
295 "OT::%c%c%c%c initial estimated table size: %u bytes.", HB_UNTAG (tag), buf_size);
296 if (unlikely (!buf.alloc (buf_size)))
297 {
298 DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c failed to allocate %u bytes.", HB_UNTAG (tag), buf_size);
299 source_blob.destroy ();
300 return false;
301 }
302
303 bool needed = false;
304 hb_serialize_context_t serializer (buf.arrayZ, buf.allocated);
305 {
306 hb_subset_context_t c (source_blob.get_blob (), plan, &serializer, tag);
307 needed = _try_subset (table, &buf, &c);
308 }
309 source_blob.destroy ();
310
311 if (serializer.in_error () && !serializer.only_offset_overflow ())
312 {
313 DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c::subset FAILED!", HB_UNTAG (tag));
314 return false;
315 }
316
317 if (!needed)
318 {
319 DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c::subset table subsetted to empty.", HB_UNTAG (tag));
320 return true;
321 }
322
323 bool result = false;
324 hb_blob_t *dest_blob = _repack (tag, serializer);
325 if (dest_blob)
326 {
327 DEBUG_MSG (SUBSET, nullptr,
328 "OT::%c%c%c%c final subset table size: %u bytes.",
329 HB_UNTAG (tag), dest_blob->length);
330 result = plan->add_table (tag, dest_blob);
331 hb_blob_destroy (dest_blob);
332 }
333
334 DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c::subset %s",
335 HB_UNTAG (tag), result ? "success" : "FAILED!");
336 return result;
337 }
338
339 static bool
340 _is_table_present (hb_face_t *source, hb_tag_t tag)
341 {
342
343 if (!hb_face_get_table_tags (source, 0, nullptr, nullptr)) {
344 // If face has 0 tables associated with it, assume that it was built from
345 // hb_face_create_tables and thus is unable to list its tables. Fallback to
346 // checking if the blob associated with tag is empty.
347 return !_table_is_empty (source, tag);
348 }
349
350 hb_tag_t table_tags[32];
351 unsigned offset = 0, num_tables = ARRAY_LENGTH (table_tags);
352 while (((void) hb_face_get_table_tags (source, offset, &num_tables, table_tags), num_tables))
353 {
354 for (unsigned i = 0; i < num_tables; ++i)
355 if (table_tags[i] == tag)
356 return true;
357 offset += num_tables;
358 }
359 return false;
360 }
361
362 static bool
363 _should_drop_table (hb_subset_plan_t *plan, hb_tag_t tag)
364 {
365 if (plan->drop_tables->has (tag))
366 return true;
367
368 switch (tag)
369 {
370 case HB_TAG ('c','v','a','r'): /* hint table, fallthrough */
371 return plan->all_axes_pinned || (plan->flags & HB_SUBSET_FLAGS_NO_HINTING);
372
373 case HB_TAG ('c','v','t',' '): /* hint table, fallthrough */
374 case HB_TAG ('f','p','g','m'): /* hint table, fallthrough */
375 case HB_TAG ('p','r','e','p'): /* hint table, fallthrough */
376 case HB_TAG ('h','d','m','x'): /* hint table, fallthrough */
377 case HB_TAG ('V','D','M','X'): /* hint table, fallthrough */
378 return plan->flags & HB_SUBSET_FLAGS_NO_HINTING;
379
380 #ifdef HB_NO_SUBSET_LAYOUT
381 // Drop Layout Tables if requested.
382 case HB_OT_TAG_GDEF:
383 case HB_OT_TAG_GPOS:
384 case HB_OT_TAG_GSUB:
385 case HB_TAG ('m','o','r','x'):
386 case HB_TAG ('m','o','r','t'):
387 case HB_TAG ('k','e','r','x'):
388 case HB_TAG ('k','e','r','n'):
389 return true;
390 #endif
391
392 case HB_TAG ('a','v','a','r'):
393 case HB_TAG ('f','v','a','r'):
394 case HB_TAG ('g','v','a','r'):
395 case HB_OT_TAG_HVAR:
396 case HB_OT_TAG_VVAR:
397 case HB_TAG ('M','V','A','R'):
398 return plan->all_axes_pinned;
399
400 default:
401 return false;
402 }
403 }
404
405 static bool
406 _passthrough (hb_subset_plan_t *plan, hb_tag_t tag)
407 {
408 hb_blob_t *source_table = hb_face_reference_table (plan->source, tag);
409 bool result = plan->add_table (tag, source_table);
410 hb_blob_destroy (source_table);
411 return result;
412 }
413
414 static bool
415 _dependencies_satisfied (hb_subset_plan_t *plan, hb_tag_t tag,
416 const hb_set_t &subsetted_tags,
417 const hb_set_t &pending_subset_tags)
418 {
419 switch (tag)
420 {
421 case HB_OT_TAG_hmtx:
422 case HB_OT_TAG_vmtx:
423 return plan->pinned_at_default || !pending_subset_tags.has (HB_OT_TAG_glyf);
424 default:
425 return true;
426 }
427 }
428
429 static bool
430 _subset_table (hb_subset_plan_t *plan,
431 hb_vector_t<char> &buf,
432 hb_tag_t tag)
433 {
434 if (plan->no_subset_tables->has (tag)) {
435 return _passthrough (plan, tag);
436 }
437
438 DEBUG_MSG (SUBSET, nullptr, "subset %c%c%c%c", HB_UNTAG (tag));
439 switch (tag)
440 {
441 case HB_OT_TAG_glyf: return _subset<const OT::glyf> (plan, buf);
442 case HB_OT_TAG_hdmx: return _subset<const OT::hdmx> (plan, buf);
443 case HB_OT_TAG_name: return _subset<const OT::name> (plan, buf);
444 case HB_OT_TAG_head:
445 if (_is_table_present (plan->source, HB_OT_TAG_glyf) && !_should_drop_table (plan, HB_OT_TAG_glyf))
446 return true; /* skip head, handled by glyf */
447 return _subset<const OT::head> (plan, buf);
448 case HB_OT_TAG_hhea: return true; /* skip hhea, handled by hmtx */
449 case HB_OT_TAG_hmtx: return _subset<const OT::hmtx> (plan, buf);
450 case HB_OT_TAG_vhea: return true; /* skip vhea, handled by vmtx */
451 case HB_OT_TAG_vmtx: return _subset<const OT::vmtx> (plan, buf);
452 case HB_OT_TAG_maxp: return _subset<const OT::maxp> (plan, buf);
453 case HB_OT_TAG_sbix: return _subset<const OT::sbix> (plan, buf);
454 case HB_OT_TAG_loca: return true; /* skip loca, handled by glyf */
455 case HB_OT_TAG_cmap: return _subset<const OT::cmap> (plan, buf);
456 case HB_OT_TAG_OS2 : return _subset<const OT::OS2 > (plan, buf);
457 case HB_OT_TAG_post: return _subset<const OT::post> (plan, buf);
458 case HB_OT_TAG_COLR: return _subset<const OT::COLR> (plan, buf);
459 case HB_OT_TAG_CPAL: return _subset<const OT::CPAL> (plan, buf);
460 case HB_OT_TAG_CBLC: return _subset<const OT::CBLC> (plan, buf);
461 case HB_OT_TAG_CBDT: return true; /* skip CBDT, handled by CBLC */
462 case HB_OT_TAG_MATH: return _subset<const OT::MATH> (plan, buf);
463
464 #ifndef HB_NO_SUBSET_CFF
465 case HB_OT_TAG_cff1: return _subset<const OT::cff1> (plan, buf);
466 case HB_OT_TAG_cff2: return _subset<const OT::cff2> (plan, buf);
467 case HB_OT_TAG_VORG: return _subset<const OT::VORG> (plan, buf);
468 #endif
469
470 #ifndef HB_NO_SUBSET_LAYOUT
471 case HB_OT_TAG_GDEF: return _subset<const OT::GDEF> (plan, buf);
472 case HB_OT_TAG_GSUB: return _subset<const GSUB> (plan, buf);
473 case HB_OT_TAG_GPOS: return _subset<const GPOS> (plan, buf);
474 case HB_OT_TAG_gvar: return _subset<const OT::gvar> (plan, buf);
475 case HB_OT_TAG_HVAR: return _subset<const OT::HVAR> (plan, buf);
476 case HB_OT_TAG_VVAR: return _subset<const OT::VVAR> (plan, buf);
477 #endif
478 case HB_OT_TAG_fvar:
479 if (plan->user_axes_location->is_empty ()) return _passthrough (plan, tag);
480 return _subset<const OT::fvar> (plan, buf);
481 case HB_OT_TAG_STAT:
482 /*TODO(qxliu): change the condition as we support more complex
483 * instancing operation*/
484 if (plan->all_axes_pinned) return _subset<const OT::STAT> (plan, buf);
485 else return _passthrough (plan, tag);
486
487 default:
488 if (plan->flags & HB_SUBSET_FLAGS_PASSTHROUGH_UNRECOGNIZED)
489 return _passthrough (plan, tag);
490
491 // Drop table
492 return true;
493 }
494 }
495
496 static void _attach_accelerator_data (hb_subset_plan_t* plan,
497 hb_face_t* face /* IN/OUT */)
498 {
499 if (!plan->inprogress_accelerator) return;
500
501 // Transfer the accelerator from the plan to us.
502 hb_subset_accelerator_t* accel = plan->inprogress_accelerator;
503 plan->inprogress_accelerator = nullptr;
504
505 if (accel->in_error ())
506 {
507 hb_subset_accelerator_t::destroy (accel);
508 return;
509 }
510
511 // Populate caches that need access to the final tables.
512 hb_blob_ptr_t<OT::cmap> cmap_ptr (hb_sanitize_context_t ().reference_table<OT::cmap> (face));
513 accel->cmap_cache = OT::cmap::create_filled_cache (cmap_ptr);
514 accel->destroy_cmap_cache = OT::SubtableUnicodesCache::destroy;
515
516 if (!hb_face_set_user_data(face,
517 hb_subset_accelerator_t::user_data_key(),
518 accel,
519 hb_subset_accelerator_t::destroy,
520 true))
521 hb_subset_accelerator_t::destroy (accel);
522 }
523
524 /**
525 * hb_subset_or_fail:
526 * @source: font face data to be subset.
527 * @input: input to use for the subsetting.
528 *
529 * Subsets a font according to provided input. Returns nullptr
530 * if the subset operation fails.
531 *
532 * Since: 2.9.0
533 **/
534 hb_face_t *
535 hb_subset_or_fail (hb_face_t *source, const hb_subset_input_t *input)
536 {
537 if (unlikely (!input || !source)) return hb_face_get_empty ();
538
539 hb_subset_plan_t *plan = hb_subset_plan_create_or_fail (source, input);
540 if (unlikely (!plan)) {
541 return nullptr;
542 }
543
544 hb_face_t * result = hb_subset_plan_execute_or_fail (plan);
545 hb_subset_plan_destroy (plan);
546 return result;
547 }
548
549
550 /**
551 * hb_subset_plan_execute_or_fail:
552 * @plan: a subsetting plan.
553 *
554 * Executes the provided subsetting @plan.
555 *
556 * Return value:
557 * on success returns a reference to generated font subset. If the subsetting operation fails
558 * returns nullptr.
559 *
560 * Since: 4.0.0
561 **/
562 hb_face_t *
563 hb_subset_plan_execute_or_fail (hb_subset_plan_t *plan)
564 {
565 if (unlikely (!plan || plan->in_error ())) {
566 return nullptr;
567 }
568
569 hb_tag_t table_tags[32];
570 unsigned offset = 0, num_tables = ARRAY_LENGTH (table_tags);
571
572 hb_set_t subsetted_tags, pending_subset_tags;
573 while (((void) _get_table_tags (plan, offset, &num_tables, table_tags), num_tables))
574 {
575 for (unsigned i = 0; i < num_tables; ++i)
576 {
577 hb_tag_t tag = table_tags[i];
578 if (_should_drop_table (plan, tag)) continue;
579 pending_subset_tags.add (tag);
580 }
581
582 offset += num_tables;
583 }
584
585 hb_vector_t<char> buf;
586 buf.alloc (4096 - 16);
587
588
589 bool success = true;
590
591 while (!pending_subset_tags.is_empty ())
592 {
593 if (subsetted_tags.in_error ()
594 || pending_subset_tags.in_error ()) {
595 success = false;
596 goto end;
597 }
598
599 bool made_changes = false;
600 for (hb_tag_t tag : pending_subset_tags)
601 {
602 if (!_dependencies_satisfied (plan, tag,
603 subsetted_tags,
604 pending_subset_tags))
605 {
606 // delayed subsetting for some tables since they might have dependency on other tables
607 // in some cases: e.g: during instantiating glyf tables, hmetrics/vmetrics are updated
608 // and saved in subset plan, hmtx/vmtx subsetting need to use these updated metrics values
609 continue;
610 }
611
612 pending_subset_tags.del (tag);
613 subsetted_tags.add (tag);
614 made_changes = true;
615
616 success = _subset_table (plan, buf, tag);
617 if (unlikely (!success)) goto end;
618 }
619
620 if (!made_changes)
621 {
622 DEBUG_MSG (SUBSET, nullptr, "Table dependencies unable to be satisfied. Subset failed.");
623 success = false;
624 goto end;
625 }
626 }
627
628 if (success && plan->attach_accelerator_data) {
629 _attach_accelerator_data (plan, plan->dest);
630 }
631
632 end:
633 return success ? hb_face_reference (plan->dest) : nullptr;
634 }