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      1 /*
      2  * Copyright  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 #ifndef HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH
     28 #define HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH
     29 
     30 #include "hb-private.hh"
     31 
     32 #include "hb-ot-shape-private.hh"
     33 #include "hb-ot-layout-gsub-table.hh"
     34 
     35 
     36 /* Features ordered the same as the entries in shaping_table rows,
     37  * followed by rlig.  Don't change. */
     38 static const hb_tag_t arabic_fallback_features[] =
     39 {
     40   HB_TAG('i','n','i','t'),
     41   HB_TAG('m','e','d','i'),
     42   HB_TAG('f','i','n','a'),
     43   HB_TAG('i','s','o','l'),
     44   HB_TAG('r','l','i','g'),
     45 };
     46 
     47 static OT::SubstLookup *
     48 arabic_fallback_synthesize_lookup_single (const hb_ot_shape_plan_t *plan HB_UNUSED,
     49 					  hb_font_t *font,
     50 					  unsigned int feature_index)
     51 {
     52   OT::GlyphID glyphs[SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1];
     53   OT::GlyphID substitutes[SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1];
     54   unsigned int num_glyphs = 0;
     55 
     56   /* Populate arrays */
     57   for (hb_codepoint_t u = SHAPING_TABLE_FIRST; u < SHAPING_TABLE_LAST + 1; u++)
     58   {
     59     hb_codepoint_t s = shaping_table[u - SHAPING_TABLE_FIRST][feature_index];
     60     hb_codepoint_t u_glyph, s_glyph;
     61 
     62     if (!s ||
     63 	!hb_font_get_glyph (font, u, 0, &u_glyph) ||
     64 	!hb_font_get_glyph (font, s, 0, &s_glyph) ||
     65 	u_glyph == s_glyph ||
     66 	u_glyph > 0xFFFFu || s_glyph > 0xFFFFu)
     67       continue;
     68 
     69     glyphs[num_glyphs].set (u_glyph);
     70     substitutes[num_glyphs].set (s_glyph);
     71 
     72     num_glyphs++;
     73   }
     74 
     75   if (!num_glyphs)
     76     return NULL;
     77 
     78   /* Bubble-sort or something equally good!
     79    * May not be good-enough for presidential candidate interviews, but good-enough for us... */
     80   hb_stable_sort (&glyphs[0], num_glyphs, OT::GlyphID::cmp, &substitutes[0]);
     81 
     82   OT::Supplier<OT::GlyphID> glyphs_supplier      (glyphs, num_glyphs);
     83   OT::Supplier<OT::GlyphID> substitutes_supplier (substitutes, num_glyphs);
     84 
     85   /* Each glyph takes four bytes max, and there's some overhead. */
     86   char buf[(SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1) * 4 + 128];
     87   OT::hb_serialize_context_t c (buf, sizeof (buf));
     88   OT::SubstLookup *lookup = c.start_serialize<OT::SubstLookup> ();
     89   bool ret = lookup->serialize_single (&c,
     90 				       OT::LookupFlag::IgnoreMarks,
     91 				       glyphs_supplier,
     92 				       substitutes_supplier,
     93 				       num_glyphs);
     94   c.end_serialize ();
     95   /* TODO sanitize the results? */
     96 
     97   return ret ? c.copy<OT::SubstLookup> () : NULL;
     98 }
     99 
    100 static OT::SubstLookup *
    101 arabic_fallback_synthesize_lookup_ligature (const hb_ot_shape_plan_t *plan HB_UNUSED,
    102 					    hb_font_t *font)
    103 {
    104   OT::GlyphID first_glyphs[ARRAY_LENGTH_CONST (ligature_table)];
    105   unsigned int first_glyphs_indirection[ARRAY_LENGTH_CONST (ligature_table)];
    106   unsigned int ligature_per_first_glyph_count_list[ARRAY_LENGTH_CONST (first_glyphs)];
    107   unsigned int num_first_glyphs = 0;
    108 
    109   /* We know that all our ligatures are 2-component */
    110   OT::GlyphID ligature_list[ARRAY_LENGTH_CONST (first_glyphs) * ARRAY_LENGTH_CONST(ligature_table[0].ligatures)];
    111   unsigned int component_count_list[ARRAY_LENGTH_CONST (ligature_list)];
    112   OT::GlyphID component_list[ARRAY_LENGTH_CONST (ligature_list) * 1/* One extra component per ligature */];
    113   unsigned int num_ligatures = 0;
    114 
    115   /* Populate arrays */
    116 
    117   /* Sort out the first-glyphs */
    118   for (unsigned int first_glyph_idx = 0; first_glyph_idx < ARRAY_LENGTH (first_glyphs); first_glyph_idx++)
    119   {
    120     hb_codepoint_t first_u = ligature_table[first_glyph_idx].first;
    121     hb_codepoint_t first_glyph;
    122     if (!hb_font_get_glyph (font, first_u, 0, &first_glyph))
    123       continue;
    124     first_glyphs[num_first_glyphs].set (first_glyph);
    125     ligature_per_first_glyph_count_list[num_first_glyphs] = 0;
    126     first_glyphs_indirection[num_first_glyphs] = first_glyph_idx;
    127     num_first_glyphs++;
    128   }
    129   hb_stable_sort (&first_glyphs[0], num_first_glyphs, OT::GlyphID::cmp, &first_glyphs_indirection[0]);
    130 
    131   /* Now that the first-glyphs are sorted, walk again, populate ligatures. */
    132   for (unsigned int i = 0; i < num_first_glyphs; i++)
    133   {
    134     unsigned int first_glyph_idx = first_glyphs_indirection[i];
    135 
    136     for (unsigned int second_glyph_idx = 0; second_glyph_idx < ARRAY_LENGTH (ligature_table[0].ligatures); second_glyph_idx++)
    137     {
    138       hb_codepoint_t second_u   = ligature_table[first_glyph_idx].ligatures[second_glyph_idx].second;
    139       hb_codepoint_t ligature_u = ligature_table[first_glyph_idx].ligatures[second_glyph_idx].ligature;
    140       hb_codepoint_t second_glyph, ligature_glyph;
    141       if (!second_u ||
    142 	  !hb_font_get_glyph (font, second_u,   0, &second_glyph) ||
    143 	  !hb_font_get_glyph (font, ligature_u, 0, &ligature_glyph))
    144 	continue;
    145 
    146       ligature_per_first_glyph_count_list[i]++;
    147 
    148       ligature_list[num_ligatures].set (ligature_glyph);
    149       component_count_list[num_ligatures] = 2;
    150       component_list[num_ligatures].set (second_glyph);
    151       num_ligatures++;
    152     }
    153   }
    154 
    155   if (!num_ligatures)
    156     return NULL;
    157 
    158   OT::Supplier<OT::GlyphID>   first_glyphs_supplier                      (first_glyphs, num_first_glyphs);
    159   OT::Supplier<unsigned int > ligature_per_first_glyph_count_supplier    (ligature_per_first_glyph_count_list, num_first_glyphs);
    160   OT::Supplier<OT::GlyphID>   ligatures_supplier                         (ligature_list, num_ligatures);
    161   OT::Supplier<unsigned int > component_count_supplier                   (component_count_list, num_ligatures);
    162   OT::Supplier<OT::GlyphID>   component_supplier                         (component_list, num_ligatures);
    163 
    164   /* 16 bytes per ligature ought to be enough... */
    165   char buf[ARRAY_LENGTH_CONST (ligature_list) * 16 + 128];
    166   OT::hb_serialize_context_t c (buf, sizeof (buf));
    167   OT::SubstLookup *lookup = c.start_serialize<OT::SubstLookup> ();
    168   bool ret = lookup->serialize_ligature (&c,
    169 					 OT::LookupFlag::IgnoreMarks,
    170 					 first_glyphs_supplier,
    171 					 ligature_per_first_glyph_count_supplier,
    172 					 num_first_glyphs,
    173 					 ligatures_supplier,
    174 					 component_count_supplier,
    175 					 component_supplier);
    176 
    177   c.end_serialize ();
    178   /* TODO sanitize the results? */
    179 
    180   return ret ? c.copy<OT::SubstLookup> () : NULL;
    181 }
    182 
    183 static OT::SubstLookup *
    184 arabic_fallback_synthesize_lookup (const hb_ot_shape_plan_t *plan,
    185 				   hb_font_t *font,
    186 				   unsigned int feature_index)
    187 {
    188   if (feature_index < 4)
    189     return arabic_fallback_synthesize_lookup_single (plan, font, feature_index);
    190   else
    191     return arabic_fallback_synthesize_lookup_ligature (plan, font);
    192 }
    193 
    194 #define ARABIC_FALLBACK_MAX_LOOKUPS 5
    195 
    196 struct arabic_fallback_plan_t
    197 {
    198   ASSERT_POD ();
    199 
    200   unsigned int num_lookups;
    201   bool free_lookups;
    202 
    203   hb_mask_t mask_array[ARABIC_FALLBACK_MAX_LOOKUPS];
    204   OT::SubstLookup *lookup_array[ARABIC_FALLBACK_MAX_LOOKUPS];
    205   hb_ot_layout_lookup_accelerator_t accel_array[ARABIC_FALLBACK_MAX_LOOKUPS];
    206 };
    207 
    208 static const arabic_fallback_plan_t arabic_fallback_plan_nil = {};
    209 
    210 #if (defined(_WIN32) || defined(__CYGWIN__)) && !defined(HB_NO_WIN1256)
    211 #define HB_WITH_WIN1256
    212 #endif
    213 
    214 #ifdef HB_WITH_WIN1256
    215 #include "hb-ot-shape-complex-arabic-win1256.hh"
    216 #endif
    217 
    218 struct ManifestLookup {
    219   OT::Tag tag;
    220   OT::OffsetTo<OT::SubstLookup> lookupOffset;
    221 };
    222 typedef OT::ArrayOf<ManifestLookup> Manifest;
    223 
    224 static bool
    225 arabic_fallback_plan_init_win1256 (arabic_fallback_plan_t *fallback_plan,
    226 				   const hb_ot_shape_plan_t *plan,
    227 				   hb_font_t *font)
    228 {
    229 #ifdef HB_WITH_WIN1256
    230   /* Does this font look like it's Windows-1256-encoded? */
    231   hb_codepoint_t g;
    232   if (!(hb_font_get_glyph (font, 0x0627u, 0, &g) && g == 199 /* ALEF */ &&
    233 	hb_font_get_glyph (font, 0x0644u, 0, &g) && g == 225 /* LAM */ &&
    234 	hb_font_get_glyph (font, 0x0649u, 0, &g) && g == 236 /* ALEF MAKSURA */ &&
    235 	hb_font_get_glyph (font, 0x064Au, 0, &g) && g == 237 /* YEH */ &&
    236 	hb_font_get_glyph (font, 0x0652u, 0, &g) && g == 250 /* SUKUN */))
    237     return false;
    238 
    239   const Manifest &manifest = reinterpret_cast<const Manifest&> (arabic_win1256_gsub_lookups.manifest);
    240   ASSERT_STATIC (sizeof (arabic_win1256_gsub_lookups.manifestData) / sizeof (ManifestLookup)
    241 		 <= ARABIC_FALLBACK_MAX_LOOKUPS);
    242   /* TODO sanitize the table? */
    243 
    244   unsigned j = 0;
    245   unsigned int count = manifest.len;
    246   for (unsigned int i = 0; i < count; i++)
    247   {
    248     fallback_plan->mask_array[j] = plan->map.get_1_mask (manifest[i].tag);
    249     if (fallback_plan->mask_array[j])
    250     {
    251       fallback_plan->lookup_array[j] = const_cast<OT::SubstLookup*> (&(&manifest+manifest[i].lookupOffset));
    252       if (fallback_plan->lookup_array[j])
    253       {
    254 	fallback_plan->accel_array[j].init (*fallback_plan->lookup_array[j]);
    255 	j++;
    256       }
    257     }
    258   }
    259 
    260   fallback_plan->num_lookups = j;
    261   fallback_plan->free_lookups = false;
    262 
    263   return j > 0;
    264 #else
    265   return false;
    266 #endif
    267 }
    268 
    269 static bool
    270 arabic_fallback_plan_init_unicode (arabic_fallback_plan_t *fallback_plan,
    271 				   const hb_ot_shape_plan_t *plan,
    272 				   hb_font_t *font)
    273 {
    274   ASSERT_STATIC (ARRAY_LENGTH_CONST(arabic_fallback_features) <= ARABIC_FALLBACK_MAX_LOOKUPS);
    275   unsigned int j = 0;
    276   for (unsigned int i = 0; i < ARRAY_LENGTH(arabic_fallback_features) ; i++)
    277   {
    278     fallback_plan->mask_array[j] = plan->map.get_1_mask (arabic_fallback_features[i]);
    279     if (fallback_plan->mask_array[j])
    280     {
    281       fallback_plan->lookup_array[j] = arabic_fallback_synthesize_lookup (plan, font, i);
    282       if (fallback_plan->lookup_array[j])
    283       {
    284 	fallback_plan->accel_array[j].init (*fallback_plan->lookup_array[j]);
    285 	j++;
    286       }
    287     }
    288   }
    289 
    290   fallback_plan->num_lookups = j;
    291   fallback_plan->free_lookups = true;
    292 
    293   return j > 0;
    294 }
    295 
    296 static arabic_fallback_plan_t *
    297 arabic_fallback_plan_create (const hb_ot_shape_plan_t *plan,
    298 			     hb_font_t *font)
    299 {
    300   arabic_fallback_plan_t *fallback_plan = (arabic_fallback_plan_t *) calloc (1, sizeof (arabic_fallback_plan_t));
    301   if (unlikely (!fallback_plan))
    302     return const_cast<arabic_fallback_plan_t *> (&arabic_fallback_plan_nil);
    303 
    304   fallback_plan->num_lookups = 0;
    305   fallback_plan->free_lookups = false;
    306 
    307   /* Try synthesizing GSUB table using Unicode Arabic Presentation Forms,
    308    * in case the font has cmap entries for the presentation-forms characters. */
    309   if (arabic_fallback_plan_init_unicode (fallback_plan, plan, font))
    310     return fallback_plan;
    311 
    312   /* See if this looks like a Windows-1256-encoded font.  If it does, use a
    313    * hand-coded GSUB table. */
    314   if (arabic_fallback_plan_init_win1256 (fallback_plan, plan, font))
    315     return fallback_plan;
    316 
    317   free (fallback_plan);
    318   return const_cast<arabic_fallback_plan_t *> (&arabic_fallback_plan_nil);
    319 }
    320 
    321 static void
    322 arabic_fallback_plan_destroy (arabic_fallback_plan_t *fallback_plan)
    323 {
    324   if (!fallback_plan || fallback_plan == &arabic_fallback_plan_nil)
    325     return;
    326 
    327   for (unsigned int i = 0; i < fallback_plan->num_lookups; i++)
    328     if (fallback_plan->lookup_array[i])
    329     {
    330       fallback_plan->accel_array[i].fini ();
    331       if (fallback_plan->free_lookups)
    332 	free (fallback_plan->lookup_array[i]);
    333     }
    334 
    335   free (fallback_plan);
    336 }
    337 
    338 static void
    339 arabic_fallback_plan_shape (arabic_fallback_plan_t *fallback_plan,
    340 			    hb_font_t *font,
    341 			    hb_buffer_t *buffer)
    342 {
    343   OT::hb_apply_context_t c (0, font, buffer);
    344   for (unsigned int i = 0; i < fallback_plan->num_lookups; i++)
    345     if (fallback_plan->lookup_array[i]) {
    346       c.set_lookup_mask (fallback_plan->mask_array[i]);
    347       hb_ot_layout_substitute_lookup (&c,
    348 				      *fallback_plan->lookup_array[i],
    349 				      fallback_plan->accel_array[i]);
    350     }
    351 }
    352 
    353 
    354 #endif /* HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH */
    355