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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-shape-complex-arabic.hh"
32  #include "hb-ot-shape.hh"
33  
34  
35  /* buffer var allocations */
36  #define arabic_shaping_action() complex_var_u8_0() /* arabic shaping action */
37  
38  #define HB_BUFFER_SCRATCH_FLAG_ARABIC_HAS_STCH HB_BUFFER_SCRATCH_FLAG_COMPLEX0
39  
40  /* See:
41   * https://github.com/harfbuzz/harfbuzz/commit/6e6f82b6f3dde0fc6c3c7d991d9ec6cfff57823d#commitcomment-14248516 */
42  #define HB_ARABIC_GENERAL_CATEGORY_IS_WORD(gen_cat) \
43  	(FLAG_UNSAFE (gen_cat) & \
44  	 (FLAG (HB_UNICODE_GENERAL_CATEGORY_UNASSIGNED) | \
45  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_PRIVATE_USE) | \
46  	  /*FLAG (HB_UNICODE_GENERAL_CATEGORY_LOWERCASE_LETTER) |*/ \
47  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_MODIFIER_LETTER) | \
48  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_OTHER_LETTER) | \
49  	  /*FLAG (HB_UNICODE_GENERAL_CATEGORY_TITLECASE_LETTER) |*/ \
50  	  /*FLAG (HB_UNICODE_GENERAL_CATEGORY_UPPERCASE_LETTER) |*/ \
51  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK) | \
52  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) | \
53  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) | \
54  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_DECIMAL_NUMBER) | \
55  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_LETTER_NUMBER) | \
56  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_OTHER_NUMBER) | \
57  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_CURRENCY_SYMBOL) | \
58  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_MODIFIER_SYMBOL) | \
59  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_MATH_SYMBOL) | \
60  	  FLAG (HB_UNICODE_GENERAL_CATEGORY_OTHER_SYMBOL)))
61  
62  
63  /*
64   * Joining types:
65   */
66  
67  /*
68   * Bits used in the joining tables
69   */
70  enum hb_arabic_joining_type_t {
71    JOINING_TYPE_U		= 0,
72    JOINING_TYPE_L		= 1,
73    JOINING_TYPE_R		= 2,
74    JOINING_TYPE_D		= 3,
75    JOINING_TYPE_C		= JOINING_TYPE_D,
76    JOINING_GROUP_ALAPH		= 4,
77    JOINING_GROUP_DALATH_RISH	= 5,
78    NUM_STATE_MACHINE_COLS	= 6,
79  
80    JOINING_TYPE_T = 7,
81    JOINING_TYPE_X = 8  /* means: use general-category to choose between U or T. */
82  };
83  
84  #include "hb-ot-shape-complex-arabic-table.hh"
85  
get_joining_type(hb_codepoint_t u,hb_unicode_general_category_t gen_cat)86  static unsigned int get_joining_type (hb_codepoint_t u, hb_unicode_general_category_t gen_cat)
87  {
88    unsigned int j_type = joining_type(u);
89    if (likely (j_type != JOINING_TYPE_X))
90      return j_type;
91  
92    return (FLAG_UNSAFE(gen_cat) &
93  	  (FLAG(HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) |
94  	   FLAG(HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) |
95  	   FLAG(HB_UNICODE_GENERAL_CATEGORY_FORMAT))
96  	 ) ?  JOINING_TYPE_T : JOINING_TYPE_U;
97  }
98  
99  #define FEATURE_IS_SYRIAC(tag) hb_in_range<unsigned char> ((unsigned char) (tag), '2', '3')
100  
101  static const hb_tag_t arabic_features[] =
102  {
103    HB_TAG('i','s','o','l'),
104    HB_TAG('f','i','n','a'),
105    HB_TAG('f','i','n','2'),
106    HB_TAG('f','i','n','3'),
107    HB_TAG('m','e','d','i'),
108    HB_TAG('m','e','d','2'),
109    HB_TAG('i','n','i','t'),
110    HB_TAG_NONE
111  };
112  
113  
114  /* Same order as the feature array */
115  enum arabic_action_t {
116    ISOL,
117    FINA,
118    FIN2,
119    FIN3,
120    MEDI,
121    MED2,
122    INIT,
123  
124    NONE,
125  
126    ARABIC_NUM_FEATURES = NONE,
127  
128    /* We abuse the same byte for other things... */
129    STCH_FIXED,
130    STCH_REPEATING,
131  };
132  
133  static const struct arabic_state_table_entry {
134  	uint8_t prev_action;
135  	uint8_t curr_action;
136  	uint16_t next_state;
137  } arabic_state_table[][NUM_STATE_MACHINE_COLS] =
138  {
139    /*   jt_U,          jt_L,          jt_R,          jt_D,          jg_ALAPH,      jg_DALATH_RISH */
140  
141    /* State 0: prev was U, not willing to join. */
142    { {NONE,NONE,0}, {NONE,ISOL,2}, {NONE,ISOL,1}, {NONE,ISOL,2}, {NONE,ISOL,1}, {NONE,ISOL,6}, },
143  
144    /* State 1: prev was R or ISOL/ALAPH, not willing to join. */
145    { {NONE,NONE,0}, {NONE,ISOL,2}, {NONE,ISOL,1}, {NONE,ISOL,2}, {NONE,FIN2,5}, {NONE,ISOL,6}, },
146  
147    /* State 2: prev was D/L in ISOL form, willing to join. */
148    { {NONE,NONE,0}, {NONE,ISOL,2}, {INIT,FINA,1}, {INIT,FINA,3}, {INIT,FINA,4}, {INIT,FINA,6}, },
149  
150    /* State 3: prev was D in FINA form, willing to join. */
151    { {NONE,NONE,0}, {NONE,ISOL,2}, {MEDI,FINA,1}, {MEDI,FINA,3}, {MEDI,FINA,4}, {MEDI,FINA,6}, },
152  
153    /* State 4: prev was FINA ALAPH, not willing to join. */
154    { {NONE,NONE,0}, {NONE,ISOL,2}, {MED2,ISOL,1}, {MED2,ISOL,2}, {MED2,FIN2,5}, {MED2,ISOL,6}, },
155  
156    /* State 5: prev was FIN2/FIN3 ALAPH, not willing to join. */
157    { {NONE,NONE,0}, {NONE,ISOL,2}, {ISOL,ISOL,1}, {ISOL,ISOL,2}, {ISOL,FIN2,5}, {ISOL,ISOL,6}, },
158  
159    /* State 6: prev was DALATH/RISH, not willing to join. */
160    { {NONE,NONE,0}, {NONE,ISOL,2}, {NONE,ISOL,1}, {NONE,ISOL,2}, {NONE,FIN3,5}, {NONE,ISOL,6}, }
161  };
162  
163  
164  static void
165  arabic_fallback_shape (const hb_ot_shape_plan_t *plan,
166  		       hb_font_t *font,
167  		       hb_buffer_t *buffer);
168  
169  static void
170  record_stch (const hb_ot_shape_plan_t *plan,
171  	     hb_font_t *font,
172  	     hb_buffer_t *buffer);
173  
174  static void
collect_features_arabic(hb_ot_shape_planner_t * plan)175  collect_features_arabic (hb_ot_shape_planner_t *plan)
176  {
177    hb_ot_map_builder_t *map = &plan->map;
178  
179    /* We apply features according to the Arabic spec, with pauses
180     * in between most.
181     *
182     * The pause between init/medi/... and rlig is required.  See eg:
183     * https://bugzilla.mozilla.org/show_bug.cgi?id=644184
184     *
185     * The pauses between init/medi/... themselves are not necessarily
186     * needed as only one of those features is applied to any character.
187     * The only difference it makes is when fonts have contextual
188     * substitutions.  We now follow the order of the spec, which makes
189     * for better experience if that's what Uniscribe is doing.
190     *
191     * At least for Arabic, looks like Uniscribe has a pause between
192     * rlig and calt.  Otherwise the IranNastaliq's ALLAH ligature won't
193     * work.  However, testing shows that rlig and calt are applied
194     * together for Mongolian in Uniscribe.  As such, we only add a
195     * pause for Arabic, not other scripts.
196     *
197     * A pause after calt is required to make KFGQPC Uthmanic Script HAFS
198     * work correctly.  See https://github.com/harfbuzz/harfbuzz/issues/505
199     */
200  
201  
202    map->enable_feature (HB_TAG('s','t','c','h'));
203    map->add_gsub_pause (record_stch);
204  
205    map->enable_feature (HB_TAG('c','c','m','p'));
206    map->enable_feature (HB_TAG('l','o','c','l'));
207  
208    map->add_gsub_pause (nullptr);
209  
210    for (unsigned int i = 0; i < ARABIC_NUM_FEATURES; i++)
211    {
212      bool has_fallback = plan->props.script == HB_SCRIPT_ARABIC && !FEATURE_IS_SYRIAC (arabic_features[i]);
213      map->add_feature (arabic_features[i], has_fallback ? F_HAS_FALLBACK : F_NONE);
214      map->add_gsub_pause (nullptr);
215    }
216  
217    /* Normally, Unicode says a ZWNJ means "don't ligate".  In Arabic script
218     * however, it says a ZWJ should also mean "don't ligate".  So we run
219     * the main ligating features as MANUAL_ZWJ. */
220  
221    map->enable_feature (HB_TAG('r','l','i','g'), F_MANUAL_ZWJ | F_HAS_FALLBACK);
222  
223    if (plan->props.script == HB_SCRIPT_ARABIC)
224      map->add_gsub_pause (arabic_fallback_shape);
225  
226    /* No pause after rclt.  See 98460779bae19e4d64d29461ff154b3527bf8420. */
227    map->enable_feature (HB_TAG('r','c','l','t'), F_MANUAL_ZWJ);
228    map->enable_feature (HB_TAG('c','a','l','t'), F_MANUAL_ZWJ);
229    map->add_gsub_pause (nullptr);
230  
231    /* And undo here. */
232  
233    /* The spec includes 'cswh'.  Earlier versions of Windows
234     * used to enable this by default, but testing suggests
235     * that Windows 8 and later do not enable it by default,
236     * and spec now says 'Off by default'.
237     * We disabled this in ae23c24c32.
238     * Note that IranNastaliq uses this feature extensively
239     * to fixup broken glyph sequences.  Oh well...
240     * Test case: U+0643,U+0640,U+0631. */
241    //map->enable_feature (HB_TAG('c','s','w','h'));
242    map->enable_feature (HB_TAG('m','s','e','t'));
243  }
244  
245  #include "hb-ot-shape-complex-arabic-fallback.hh"
246  
247  struct arabic_shape_plan_t
248  {
249    /* The "+ 1" in the next array is to accommodate for the "NONE" command,
250     * which is not an OpenType feature, but this simplifies the code by not
251     * having to do a "if (... < NONE) ..." and just rely on the fact that
252     * mask_array[NONE] == 0. */
253    hb_mask_t mask_array[ARABIC_NUM_FEATURES + 1];
254  
255    hb_atomic_ptr_t<arabic_fallback_plan_t> fallback_plan;
256  
257    unsigned int do_fallback : 1;
258    unsigned int has_stch : 1;
259  };
260  
261  void *
data_create_arabic(const hb_ot_shape_plan_t * plan)262  data_create_arabic (const hb_ot_shape_plan_t *plan)
263  {
264    arabic_shape_plan_t *arabic_plan = (arabic_shape_plan_t *) calloc (1, sizeof (arabic_shape_plan_t));
265    if (unlikely (!arabic_plan))
266      return nullptr;
267  
268    arabic_plan->do_fallback = plan->props.script == HB_SCRIPT_ARABIC;
269    arabic_plan->has_stch = !!plan->map.get_1_mask (HB_TAG ('s','t','c','h'));
270    for (unsigned int i = 0; i < ARABIC_NUM_FEATURES; i++) {
271      arabic_plan->mask_array[i] = plan->map.get_1_mask (arabic_features[i]);
272      arabic_plan->do_fallback = arabic_plan->do_fallback &&
273  			       (FEATURE_IS_SYRIAC (arabic_features[i]) ||
274  			        plan->map.needs_fallback (arabic_features[i]));
275    }
276  
277    return arabic_plan;
278  }
279  
280  void
data_destroy_arabic(void * data)281  data_destroy_arabic (void *data)
282  {
283    arabic_shape_plan_t *arabic_plan = (arabic_shape_plan_t *) data;
284  
285    arabic_fallback_plan_destroy (arabic_plan->fallback_plan);
286  
287    free (data);
288  }
289  
290  static void
arabic_joining(hb_buffer_t * buffer)291  arabic_joining (hb_buffer_t *buffer)
292  {
293    unsigned int count = buffer->len;
294    hb_glyph_info_t *info = buffer->info;
295    unsigned int prev = (unsigned int) -1, state = 0;
296  
297    /* Check pre-context */
298    for (unsigned int i = 0; i < buffer->context_len[0]; i++)
299    {
300      unsigned int this_type = get_joining_type (buffer->context[0][i], buffer->unicode->general_category (buffer->context[0][i]));
301  
302      if (unlikely (this_type == JOINING_TYPE_T))
303        continue;
304  
305      const arabic_state_table_entry *entry = &arabic_state_table[state][this_type];
306      state = entry->next_state;
307      break;
308    }
309  
310    for (unsigned int i = 0; i < count; i++)
311    {
312      unsigned int this_type = get_joining_type (info[i].codepoint, _hb_glyph_info_get_general_category (&info[i]));
313  
314      if (unlikely (this_type == JOINING_TYPE_T)) {
315        info[i].arabic_shaping_action() = NONE;
316        continue;
317      }
318  
319      const arabic_state_table_entry *entry = &arabic_state_table[state][this_type];
320  
321      if (entry->prev_action != NONE && prev != (unsigned int) -1)
322      {
323        info[prev].arabic_shaping_action() = entry->prev_action;
324        buffer->unsafe_to_break (prev, i + 1);
325      }
326  
327      info[i].arabic_shaping_action() = entry->curr_action;
328  
329      prev = i;
330      state = entry->next_state;
331    }
332  
333    for (unsigned int i = 0; i < buffer->context_len[1]; i++)
334    {
335      unsigned int this_type = get_joining_type (buffer->context[1][i], buffer->unicode->general_category (buffer->context[1][i]));
336  
337      if (unlikely (this_type == JOINING_TYPE_T))
338        continue;
339  
340      const arabic_state_table_entry *entry = &arabic_state_table[state][this_type];
341      if (entry->prev_action != NONE && prev != (unsigned int) -1)
342        info[prev].arabic_shaping_action() = entry->prev_action;
343      break;
344    }
345  }
346  
347  static void
mongolian_variation_selectors(hb_buffer_t * buffer)348  mongolian_variation_selectors (hb_buffer_t *buffer)
349  {
350    /* Copy arabic_shaping_action() from base to Mongolian variation selectors. */
351    unsigned int count = buffer->len;
352    hb_glyph_info_t *info = buffer->info;
353    for (unsigned int i = 1; i < count; i++)
354      if (unlikely (hb_in_range<hb_codepoint_t> (info[i].codepoint, 0x180Bu, 0x180Du)))
355        info[i].arabic_shaping_action() = info[i - 1].arabic_shaping_action();
356  }
357  
358  void
setup_masks_arabic_plan(const arabic_shape_plan_t * arabic_plan,hb_buffer_t * buffer,hb_script_t script)359  setup_masks_arabic_plan (const arabic_shape_plan_t *arabic_plan,
360  			 hb_buffer_t               *buffer,
361  			 hb_script_t                script)
362  {
363    HB_BUFFER_ALLOCATE_VAR (buffer, arabic_shaping_action);
364  
365    arabic_joining (buffer);
366    if (script == HB_SCRIPT_MONGOLIAN)
367      mongolian_variation_selectors (buffer);
368  
369    unsigned int count = buffer->len;
370    hb_glyph_info_t *info = buffer->info;
371    for (unsigned int i = 0; i < count; i++)
372      info[i].mask |= arabic_plan->mask_array[info[i].arabic_shaping_action()];
373  }
374  
375  static void
setup_masks_arabic(const hb_ot_shape_plan_t * plan,hb_buffer_t * buffer,hb_font_t * font HB_UNUSED)376  setup_masks_arabic (const hb_ot_shape_plan_t *plan,
377  		    hb_buffer_t              *buffer,
378  		    hb_font_t                *font HB_UNUSED)
379  {
380    const arabic_shape_plan_t *arabic_plan = (const arabic_shape_plan_t *) plan->data;
381    setup_masks_arabic_plan (arabic_plan, buffer, plan->props.script);
382  }
383  
384  static void
arabic_fallback_shape(const hb_ot_shape_plan_t * plan,hb_font_t * font,hb_buffer_t * buffer)385  arabic_fallback_shape (const hb_ot_shape_plan_t *plan,
386  		       hb_font_t *font,
387  		       hb_buffer_t *buffer)
388  {
389  #ifdef HB_NO_OT_SHAPE_COMPLEX_ARABIC_FALLBACK
390    return;
391  #endif
392  
393    const arabic_shape_plan_t *arabic_plan = (const arabic_shape_plan_t *) plan->data;
394  
395    if (!arabic_plan->do_fallback)
396      return;
397  
398  retry:
399    arabic_fallback_plan_t *fallback_plan = arabic_plan->fallback_plan;
400    if (unlikely (!fallback_plan))
401    {
402      /* This sucks.  We need a font to build the fallback plan... */
403      fallback_plan = arabic_fallback_plan_create (plan, font);
404      if (unlikely (!arabic_plan->fallback_plan.cmpexch (nullptr, fallback_plan)))
405      {
406        arabic_fallback_plan_destroy (fallback_plan);
407        goto retry;
408      }
409    }
410  
411    arabic_fallback_plan_shape (fallback_plan, font, buffer);
412  }
413  
414  /*
415   * Stretch feature: "stch".
416   * See example here:
417   * https://docs.microsoft.com/en-us/typography/script-development/syriac
418   * We implement this in a generic way, such that the Arabic subtending
419   * marks can use it as well.
420   */
421  
422  static void
record_stch(const hb_ot_shape_plan_t * plan,hb_font_t * font HB_UNUSED,hb_buffer_t * buffer)423  record_stch (const hb_ot_shape_plan_t *plan,
424  	     hb_font_t *font HB_UNUSED,
425  	     hb_buffer_t *buffer)
426  {
427    const arabic_shape_plan_t *arabic_plan = (const arabic_shape_plan_t *) plan->data;
428    if (!arabic_plan->has_stch)
429      return;
430  
431    /* 'stch' feature was just applied.  Look for anything that multiplied,
432     * and record it for stch treatment later.  Note that rtlm, frac, etc
433     * are applied before stch, but we assume that they didn't result in
434     * anything multiplying into 5 pieces, so it's safe-ish... */
435  
436    unsigned int count = buffer->len;
437    hb_glyph_info_t *info = buffer->info;
438    for (unsigned int i = 0; i < count; i++)
439      if (unlikely (_hb_glyph_info_multiplied (&info[i])))
440      {
441        unsigned int comp = _hb_glyph_info_get_lig_comp (&info[i]);
442        info[i].arabic_shaping_action() = comp % 2 ? STCH_REPEATING : STCH_FIXED;
443        buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_ARABIC_HAS_STCH;
444      }
445  }
446  
447  static void
apply_stch(const hb_ot_shape_plan_t * plan HB_UNUSED,hb_buffer_t * buffer,hb_font_t * font)448  apply_stch (const hb_ot_shape_plan_t *plan HB_UNUSED,
449  	    hb_buffer_t              *buffer,
450  	    hb_font_t                *font)
451  {
452    if (likely (!(buffer->scratch_flags & HB_BUFFER_SCRATCH_FLAG_ARABIC_HAS_STCH)))
453      return;
454  
455    /* The Arabic shaper currently always processes in RTL mode, so we should
456     * stretch / position the stretched pieces to the left / preceding glyphs. */
457  
458    /* We do a two pass implementation:
459     * First pass calculates the exact number of extra glyphs we need,
460     * We then enlarge buffer to have that much room,
461     * Second pass applies the stretch, copying things to the end of buffer.
462     */
463  
464    int sign = font->x_scale < 0 ? -1 : +1;
465    unsigned int extra_glyphs_needed = 0; // Set during MEASURE, used during CUT
466    enum { MEASURE, CUT } /* step_t */;
467  
468    for (unsigned int step = MEASURE; step <= CUT; step = step + 1)
469    {
470      unsigned int count = buffer->len;
471      hb_glyph_info_t *info = buffer->info;
472      hb_glyph_position_t *pos = buffer->pos;
473      unsigned int new_len = count + extra_glyphs_needed; // write head during CUT
474      unsigned int j = new_len;
475      for (unsigned int i = count; i; i--)
476      {
477        if (!hb_in_range<uint8_t> (info[i - 1].arabic_shaping_action(), STCH_FIXED, STCH_REPEATING))
478        {
479  	if (step == CUT)
480  	{
481  	  --j;
482  	  info[j] = info[i - 1];
483  	  pos[j] = pos[i - 1];
484  	}
485  	continue;
486        }
487  
488        /* Yay, justification! */
489  
490        hb_position_t w_total = 0; // Total to be filled
491        hb_position_t w_fixed = 0; // Sum of fixed tiles
492        hb_position_t w_repeating = 0; // Sum of repeating tiles
493        int n_fixed = 0;
494        int n_repeating = 0;
495  
496        unsigned int end = i;
497        while (i &&
498  	     hb_in_range<uint8_t> (info[i - 1].arabic_shaping_action(), STCH_FIXED, STCH_REPEATING))
499        {
500  	i--;
501  	hb_position_t width = font->get_glyph_h_advance (info[i].codepoint);
502  	if (info[i].arabic_shaping_action() == STCH_FIXED)
503  	{
504  	  w_fixed += width;
505  	  n_fixed++;
506  	}
507  	else
508  	{
509  	  w_repeating += width;
510  	  n_repeating++;
511  	}
512        }
513        unsigned int start = i;
514        unsigned int context = i;
515        while (context &&
516  	     !hb_in_range<uint8_t> (info[context - 1].arabic_shaping_action(), STCH_FIXED, STCH_REPEATING) &&
517  	     (_hb_glyph_info_is_default_ignorable (&info[context - 1]) ||
518  	      HB_ARABIC_GENERAL_CATEGORY_IS_WORD (_hb_glyph_info_get_general_category (&info[context - 1]))))
519        {
520  	context--;
521  	w_total += pos[context].x_advance;
522        }
523        i++; // Don't touch i again.
524  
525        DEBUG_MSG (ARABIC, nullptr, "%s stretch at (%d,%d,%d)",
526  		 step == MEASURE ? "measuring" : "cutting", context, start, end);
527        DEBUG_MSG (ARABIC, nullptr, "rest of word:    count=%d width %d", start - context, w_total);
528        DEBUG_MSG (ARABIC, nullptr, "fixed tiles:     count=%d width=%d", n_fixed, w_fixed);
529        DEBUG_MSG (ARABIC, nullptr, "repeating tiles: count=%d width=%d", n_repeating, w_repeating);
530  
531        /* Number of additional times to repeat each repeating tile. */
532        int n_copies = 0;
533  
534        hb_position_t w_remaining = w_total - w_fixed;
535        if (sign * w_remaining > sign * w_repeating && sign * w_repeating > 0)
536  	n_copies = (sign * w_remaining) / (sign * w_repeating) - 1;
537  
538        /* See if we can improve the fit by adding an extra repeat and squeezing them together a bit. */
539        hb_position_t extra_repeat_overlap = 0;
540        hb_position_t shortfall = sign * w_remaining - sign * w_repeating * (n_copies + 1);
541        if (shortfall > 0 && n_repeating > 0)
542        {
543  	++n_copies;
544  	hb_position_t excess = (n_copies + 1) * sign * w_repeating - sign * w_remaining;
545  	if (excess > 0)
546  	  extra_repeat_overlap = excess / (n_copies * n_repeating);
547        }
548  
549        if (step == MEASURE)
550        {
551  	extra_glyphs_needed += n_copies * n_repeating;
552  	DEBUG_MSG (ARABIC, nullptr, "will add extra %d copies of repeating tiles", n_copies);
553        }
554        else
555        {
556  	buffer->unsafe_to_break (context, end);
557  	hb_position_t x_offset = 0;
558  	for (unsigned int k = end; k > start; k--)
559  	{
560  	  hb_position_t width = font->get_glyph_h_advance (info[k - 1].codepoint);
561  
562  	  unsigned int repeat = 1;
563  	  if (info[k - 1].arabic_shaping_action() == STCH_REPEATING)
564  	    repeat += n_copies;
565  
566  	  DEBUG_MSG (ARABIC, nullptr, "appending %d copies of glyph %d; j=%d",
567  		     repeat, info[k - 1].codepoint, j);
568  	  for (unsigned int n = 0; n < repeat; n++)
569  	  {
570  	    x_offset -= width;
571  	    if (n > 0)
572  	      x_offset += extra_repeat_overlap;
573  	    pos[k - 1].x_offset = x_offset;
574  	    /* Append copy. */
575  	    --j;
576  	    info[j] = info[k - 1];
577  	    pos[j] = pos[k - 1];
578  	  }
579  	}
580        }
581      }
582  
583      if (step == MEASURE)
584      {
585        if (unlikely (!buffer->ensure (count + extra_glyphs_needed)))
586  	break;
587      }
588      else
589      {
590        assert (j == 0);
591        buffer->len = new_len;
592      }
593    }
594  }
595  
596  
597  static void
postprocess_glyphs_arabic(const hb_ot_shape_plan_t * plan,hb_buffer_t * buffer,hb_font_t * font)598  postprocess_glyphs_arabic (const hb_ot_shape_plan_t *plan,
599  			   hb_buffer_t              *buffer,
600  			   hb_font_t                *font)
601  {
602    apply_stch (plan, buffer, font);
603  
604    HB_BUFFER_DEALLOCATE_VAR (buffer, arabic_shaping_action);
605  }
606  
607  /* http://www.unicode.org/reports/tr53/ */
608  
609  static hb_codepoint_t
610  modifier_combining_marks[] =
611  {
612    0x0654u, /* ARABIC HAMZA ABOVE */
613    0x0655u, /* ARABIC HAMZA BELOW */
614    0x0658u, /* ARABIC MARK NOON GHUNNA */
615    0x06DCu, /* ARABIC SMALL HIGH SEEN */
616    0x06E3u, /* ARABIC SMALL LOW SEEN */
617    0x06E7u, /* ARABIC SMALL HIGH YEH */
618    0x06E8u, /* ARABIC SMALL HIGH NOON */
619    0x08D3u, /* ARABIC SMALL LOW WAW */
620    0x08F3u, /* ARABIC SMALL HIGH WAW */
621  };
622  
623  static inline bool
info_is_mcm(const hb_glyph_info_t & info)624  info_is_mcm (const hb_glyph_info_t &info)
625  {
626    hb_codepoint_t u = info.codepoint;
627    for (unsigned int i = 0; i < ARRAY_LENGTH (modifier_combining_marks); i++)
628      if (u == modifier_combining_marks[i])
629        return true;
630    return false;
631  }
632  
633  static void
reorder_marks_arabic(const hb_ot_shape_plan_t * plan HB_UNUSED,hb_buffer_t * buffer,unsigned int start,unsigned int end)634  reorder_marks_arabic (const hb_ot_shape_plan_t *plan HB_UNUSED,
635  		      hb_buffer_t              *buffer,
636  		      unsigned int              start,
637  		      unsigned int              end)
638  {
639    hb_glyph_info_t *info = buffer->info;
640  
641    DEBUG_MSG (ARABIC, buffer, "Reordering marks from %d to %d", start, end);
642  
643    unsigned int i = start;
644    for (unsigned int cc = 220; cc <= 230; cc += 10)
645    {
646      DEBUG_MSG (ARABIC, buffer, "Looking for %d's starting at %d", cc, i);
647      while (i < end && info_cc(info[i]) < cc)
648        i++;
649      DEBUG_MSG (ARABIC, buffer, "Looking for %d's stopped at %d", cc, i);
650  
651      if (i == end)
652        break;
653  
654      if (info_cc(info[i]) > cc)
655        continue;
656  
657      unsigned int j = i;
658      while (j < end && info_cc(info[j]) == cc && info_is_mcm (info[j]))
659        j++;
660  
661      if (i == j)
662        continue;
663  
664      DEBUG_MSG (ARABIC, buffer, "Found %d's from %d to %d", cc, i, j);
665  
666      /* Shift it! */
667      DEBUG_MSG (ARABIC, buffer, "Shifting %d's: %d %d", cc, i, j);
668      hb_glyph_info_t temp[HB_OT_SHAPE_COMPLEX_MAX_COMBINING_MARKS];
669      assert (j - i <= ARRAY_LENGTH (temp));
670      buffer->merge_clusters (start, j);
671      memmove (temp, &info[i], (j - i) * sizeof (hb_glyph_info_t));
672      memmove (&info[start + j - i], &info[start], (i - start) * sizeof (hb_glyph_info_t));
673      memmove (&info[start], temp, (j - i) * sizeof (hb_glyph_info_t));
674  
675      /* Renumber CC such that the reordered sequence is still sorted.
676       * 22 and 26 are chosen because they are smaller than all Arabic categories,
677       * and are folded back to 220/230 respectively during fallback mark positioning.
678       *
679       * We do this because the CGJ-handling logic in the normalizer relies on
680       * mark sequences having an increasing order even after this reordering.
681       * https://github.com/harfbuzz/harfbuzz/issues/554
682       * This, however, does break some obscure sequences, where the normalizer
683       * might compose a sequence that it should not.  For example, in the seequence
684       * ALEF, HAMZAH, MADDAH, we should NOT try to compose ALEF+MADDAH, but with this
685       * renumbering, we will.
686       */
687      unsigned int new_start = start + j - i;
688      unsigned int new_cc = cc == 220 ? HB_MODIFIED_COMBINING_CLASS_CCC22 : HB_MODIFIED_COMBINING_CLASS_CCC26;
689      while (start < new_start)
690      {
691        _hb_glyph_info_set_modified_combining_class (&info[start], new_cc);
692        start++;
693      }
694  
695      i = j;
696    }
697  }
698  
699  const hb_ot_complex_shaper_t _hb_ot_complex_shaper_arabic =
700  {
701    collect_features_arabic,
702    nullptr, /* override_features */
703    data_create_arabic,
704    data_destroy_arabic,
705    nullptr, /* preprocess_text */
706    postprocess_glyphs_arabic,
707    HB_OT_SHAPE_NORMALIZATION_MODE_DEFAULT,
708    nullptr, /* decompose */
709    nullptr, /* compose */
710    setup_masks_arabic,
711    HB_TAG_NONE, /* gpos_tag */
712    reorder_marks_arabic,
713    HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_GDEF_LATE,
714    true, /* fallback_position */
715  };
716  
717  
718  #endif
719