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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.hh"
31 
32 #include "hb-ot-shape.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 *
arabic_fallback_synthesize_lookup_single(const hb_ot_shape_plan_t * plan HB_UNUSED,hb_font_t * font,unsigned int feature_index)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 nullptr;
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, (int(*)(const OT::GlyphID*, const OT::GlyphID *)) OT::GlyphID::cmp, &substitutes[0]);
81 
82 
83   /* Each glyph takes four bytes max, and there's some overhead. */
84   char buf[(SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1) * 4 + 128];
85   hb_serialize_context_t c (buf, sizeof (buf));
86   OT::SubstLookup *lookup = c.start_serialize<OT::SubstLookup> ();
87   bool ret = lookup->serialize_single (&c,
88 				       OT::LookupFlag::IgnoreMarks,
89 				       hb_array (glyphs, num_glyphs),
90 				       hb_array (substitutes, num_glyphs));
91   c.end_serialize ();
92   /* TODO sanitize the results? */
93 
94   return ret ? c.copy<OT::SubstLookup> () : nullptr;
95 }
96 
97 static OT::SubstLookup *
arabic_fallback_synthesize_lookup_ligature(const hb_ot_shape_plan_t * plan HB_UNUSED,hb_font_t * font)98 arabic_fallback_synthesize_lookup_ligature (const hb_ot_shape_plan_t *plan HB_UNUSED,
99 					    hb_font_t *font)
100 {
101   OT::GlyphID first_glyphs[ARRAY_LENGTH_CONST (ligature_table)];
102   unsigned int first_glyphs_indirection[ARRAY_LENGTH_CONST (ligature_table)];
103   unsigned int ligature_per_first_glyph_count_list[ARRAY_LENGTH_CONST (first_glyphs)];
104   unsigned int num_first_glyphs = 0;
105 
106   /* We know that all our ligatures are 2-component */
107   OT::GlyphID ligature_list[ARRAY_LENGTH_CONST (first_glyphs) * ARRAY_LENGTH_CONST(ligature_table[0].ligatures)];
108   unsigned int component_count_list[ARRAY_LENGTH_CONST (ligature_list)];
109   OT::GlyphID component_list[ARRAY_LENGTH_CONST (ligature_list) * 1/* One extra component per ligature */];
110   unsigned int num_ligatures = 0;
111 
112   /* Populate arrays */
113 
114   /* Sort out the first-glyphs */
115   for (unsigned int first_glyph_idx = 0; first_glyph_idx < ARRAY_LENGTH (first_glyphs); first_glyph_idx++)
116   {
117     hb_codepoint_t first_u = ligature_table[first_glyph_idx].first;
118     hb_codepoint_t first_glyph;
119     if (!hb_font_get_glyph (font, first_u, 0, &first_glyph))
120       continue;
121     first_glyphs[num_first_glyphs].set (first_glyph);
122     ligature_per_first_glyph_count_list[num_first_glyphs] = 0;
123     first_glyphs_indirection[num_first_glyphs] = first_glyph_idx;
124     num_first_glyphs++;
125   }
126   hb_stable_sort (&first_glyphs[0], num_first_glyphs, (int(*)(const OT::GlyphID*, const OT::GlyphID *)) OT::GlyphID::cmp, &first_glyphs_indirection[0]);
127 
128   /* Now that the first-glyphs are sorted, walk again, populate ligatures. */
129   for (unsigned int i = 0; i < num_first_glyphs; i++)
130   {
131     unsigned int first_glyph_idx = first_glyphs_indirection[i];
132 
133     for (unsigned int second_glyph_idx = 0; second_glyph_idx < ARRAY_LENGTH (ligature_table[0].ligatures); second_glyph_idx++)
134     {
135       hb_codepoint_t second_u   = ligature_table[first_glyph_idx].ligatures[second_glyph_idx].second;
136       hb_codepoint_t ligature_u = ligature_table[first_glyph_idx].ligatures[second_glyph_idx].ligature;
137       hb_codepoint_t second_glyph, ligature_glyph;
138       if (!second_u ||
139 	  !hb_font_get_glyph (font, second_u,   0, &second_glyph) ||
140 	  !hb_font_get_glyph (font, ligature_u, 0, &ligature_glyph))
141 	continue;
142 
143       ligature_per_first_glyph_count_list[i]++;
144 
145       ligature_list[num_ligatures].set (ligature_glyph);
146       component_count_list[num_ligatures] = 2;
147       component_list[num_ligatures].set (second_glyph);
148       num_ligatures++;
149     }
150   }
151 
152   if (!num_ligatures)
153     return nullptr;
154 
155 
156   /* 16 bytes per ligature ought to be enough... */
157   char buf[ARRAY_LENGTH_CONST (ligature_list) * 16 + 128];
158   hb_serialize_context_t c (buf, sizeof (buf));
159   OT::SubstLookup *lookup = c.start_serialize<OT::SubstLookup> ();
160   bool ret = lookup->serialize_ligature (&c,
161 					 OT::LookupFlag::IgnoreMarks,
162 					 hb_array (first_glyphs, num_first_glyphs),
163 					 hb_array (ligature_per_first_glyph_count_list, num_first_glyphs),
164 					 hb_array (ligature_list, num_ligatures),
165 					 hb_array (component_count_list, num_ligatures),
166 					 hb_array (component_list, num_ligatures));
167   c.end_serialize ();
168   /* TODO sanitize the results? */
169 
170   return ret ? c.copy<OT::SubstLookup> () : nullptr;
171 }
172 
173 static OT::SubstLookup *
arabic_fallback_synthesize_lookup(const hb_ot_shape_plan_t * plan,hb_font_t * font,unsigned int feature_index)174 arabic_fallback_synthesize_lookup (const hb_ot_shape_plan_t *plan,
175 				   hb_font_t *font,
176 				   unsigned int feature_index)
177 {
178   if (feature_index < 4)
179     return arabic_fallback_synthesize_lookup_single (plan, font, feature_index);
180   else
181     return arabic_fallback_synthesize_lookup_ligature (plan, font);
182 }
183 
184 #define ARABIC_FALLBACK_MAX_LOOKUPS 5
185 
186 struct arabic_fallback_plan_t
187 {
188   unsigned int num_lookups;
189   bool free_lookups;
190 
191   hb_mask_t mask_array[ARABIC_FALLBACK_MAX_LOOKUPS];
192   OT::SubstLookup *lookup_array[ARABIC_FALLBACK_MAX_LOOKUPS];
193   OT::hb_ot_layout_lookup_accelerator_t accel_array[ARABIC_FALLBACK_MAX_LOOKUPS];
194 };
195 
196 #if defined(_WIN32) && !defined(HB_NO_WIN1256)
197 #define HB_WITH_WIN1256
198 #endif
199 
200 #ifdef HB_WITH_WIN1256
201 #include "hb-ot-shape-complex-arabic-win1256.hh"
202 #endif
203 
204 struct ManifestLookup
205 {
206   public:
207   OT::Tag tag;
208   OT::OffsetTo<OT::SubstLookup> lookupOffset;
209   public:
210   DEFINE_SIZE_STATIC (6);
211 };
212 typedef OT::ArrayOf<ManifestLookup> Manifest;
213 
214 static bool
arabic_fallback_plan_init_win1256(arabic_fallback_plan_t * fallback_plan HB_UNUSED,const hb_ot_shape_plan_t * plan HB_UNUSED,hb_font_t * font HB_UNUSED)215 arabic_fallback_plan_init_win1256 (arabic_fallback_plan_t *fallback_plan HB_UNUSED,
216 				   const hb_ot_shape_plan_t *plan HB_UNUSED,
217 				   hb_font_t *font HB_UNUSED)
218 {
219 #ifdef HB_WITH_WIN1256
220   /* Does this font look like it's Windows-1256-encoded? */
221   hb_codepoint_t g;
222   if (!(hb_font_get_glyph (font, 0x0627u, 0, &g) && g == 199 /* ALEF */ &&
223 	hb_font_get_glyph (font, 0x0644u, 0, &g) && g == 225 /* LAM */ &&
224 	hb_font_get_glyph (font, 0x0649u, 0, &g) && g == 236 /* ALEF MAKSURA */ &&
225 	hb_font_get_glyph (font, 0x064Au, 0, &g) && g == 237 /* YEH */ &&
226 	hb_font_get_glyph (font, 0x0652u, 0, &g) && g == 250 /* SUKUN */))
227     return false;
228 
229   const Manifest &manifest = reinterpret_cast<const Manifest&> (arabic_win1256_gsub_lookups.manifest);
230   static_assert (sizeof (arabic_win1256_gsub_lookups.manifestData) / sizeof (ManifestLookup)
231 		 <= ARABIC_FALLBACK_MAX_LOOKUPS, "");
232   /* TODO sanitize the table? */
233 
234   unsigned j = 0;
235   unsigned int count = manifest.len;
236   for (unsigned int i = 0; i < count; i++)
237   {
238     fallback_plan->mask_array[j] = plan->map.get_1_mask (manifest[i].tag);
239     if (fallback_plan->mask_array[j])
240     {
241       fallback_plan->lookup_array[j] = const_cast<OT::SubstLookup*> (&(&manifest+manifest[i].lookupOffset));
242       if (fallback_plan->lookup_array[j])
243       {
244 	fallback_plan->accel_array[j].init (*fallback_plan->lookup_array[j]);
245 	j++;
246       }
247     }
248   }
249 
250   fallback_plan->num_lookups = j;
251   fallback_plan->free_lookups = false;
252 
253   return j > 0;
254 #else
255   return false;
256 #endif
257 }
258 
259 static bool
arabic_fallback_plan_init_unicode(arabic_fallback_plan_t * fallback_plan,const hb_ot_shape_plan_t * plan,hb_font_t * font)260 arabic_fallback_plan_init_unicode (arabic_fallback_plan_t *fallback_plan,
261 				   const hb_ot_shape_plan_t *plan,
262 				   hb_font_t *font)
263 {
264   static_assert ((ARRAY_LENGTH_CONST(arabic_fallback_features) <= ARABIC_FALLBACK_MAX_LOOKUPS), "");
265   unsigned int j = 0;
266   for (unsigned int i = 0; i < ARRAY_LENGTH(arabic_fallback_features) ; i++)
267   {
268     fallback_plan->mask_array[j] = plan->map.get_1_mask (arabic_fallback_features[i]);
269     if (fallback_plan->mask_array[j])
270     {
271       fallback_plan->lookup_array[j] = arabic_fallback_synthesize_lookup (plan, font, i);
272       if (fallback_plan->lookup_array[j])
273       {
274 	fallback_plan->accel_array[j].init (*fallback_plan->lookup_array[j]);
275 	j++;
276       }
277     }
278   }
279 
280   fallback_plan->num_lookups = j;
281   fallback_plan->free_lookups = true;
282 
283   return j > 0;
284 }
285 
286 static arabic_fallback_plan_t *
arabic_fallback_plan_create(const hb_ot_shape_plan_t * plan,hb_font_t * font)287 arabic_fallback_plan_create (const hb_ot_shape_plan_t *plan,
288 			     hb_font_t *font)
289 {
290   arabic_fallback_plan_t *fallback_plan = (arabic_fallback_plan_t *) calloc (1, sizeof (arabic_fallback_plan_t));
291   if (unlikely (!fallback_plan))
292     return const_cast<arabic_fallback_plan_t *> (&Null(arabic_fallback_plan_t));
293 
294   fallback_plan->num_lookups = 0;
295   fallback_plan->free_lookups = false;
296 
297   /* Try synthesizing GSUB table using Unicode Arabic Presentation Forms,
298    * in case the font has cmap entries for the presentation-forms characters. */
299   if (arabic_fallback_plan_init_unicode (fallback_plan, plan, font))
300     return fallback_plan;
301 
302   /* See if this looks like a Windows-1256-encoded font.  If it does, use a
303    * hand-coded GSUB table. */
304   if (arabic_fallback_plan_init_win1256 (fallback_plan, plan, font))
305     return fallback_plan;
306 
307   assert (fallback_plan->num_lookups == 0);
308   free (fallback_plan);
309   return const_cast<arabic_fallback_plan_t *> (&Null(arabic_fallback_plan_t));
310 }
311 
312 static void
arabic_fallback_plan_destroy(arabic_fallback_plan_t * fallback_plan)313 arabic_fallback_plan_destroy (arabic_fallback_plan_t *fallback_plan)
314 {
315   if (!fallback_plan || fallback_plan->num_lookups == 0)
316     return;
317 
318   for (unsigned int i = 0; i < fallback_plan->num_lookups; i++)
319     if (fallback_plan->lookup_array[i])
320     {
321       fallback_plan->accel_array[i].fini ();
322       if (fallback_plan->free_lookups)
323 	free (fallback_plan->lookup_array[i]);
324     }
325 
326   free (fallback_plan);
327 }
328 
329 static void
arabic_fallback_plan_shape(arabic_fallback_plan_t * fallback_plan,hb_font_t * font,hb_buffer_t * buffer)330 arabic_fallback_plan_shape (arabic_fallback_plan_t *fallback_plan,
331 			    hb_font_t *font,
332 			    hb_buffer_t *buffer)
333 {
334   OT::hb_ot_apply_context_t c (0, font, buffer);
335   for (unsigned int i = 0; i < fallback_plan->num_lookups; i++)
336     if (fallback_plan->lookup_array[i]) {
337       c.set_lookup_mask (fallback_plan->mask_array[i]);
338       hb_ot_layout_substitute_lookup (&c,
339 				      *fallback_plan->lookup_array[i],
340 				      fallback_plan->accel_array[i]);
341     }
342 }
343 
344 
345 #endif /* HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH */
346