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-ot-shape-complex-private.hh"
28
29
30/* Thai / Lao shaper */
31
32
33/* PUA shaping */
34
35
36enum thai_consonant_type_t
37{
38  NC,
39  AC,
40  RC,
41  DC,
42  NOT_CONSONANT,
43  NUM_CONSONANT_TYPES = NOT_CONSONANT
44};
45
46static thai_consonant_type_t
47get_consonant_type (hb_codepoint_t u)
48{
49  if (u == 0x0E1Bu || u == 0x0E1Du || u == 0x0E1Fu/* || u == 0x0E2Cu*/)
50    return AC;
51  if (u == 0x0E0Du || u == 0x0E10u)
52    return RC;
53  if (u == 0x0E0Eu || u == 0x0E0Fu)
54    return DC;
55  if (hb_in_range (u, 0x0E01u, 0x0E2Eu))
56    return NC;
57  return NOT_CONSONANT;
58}
59
60
61enum thai_mark_type_t
62{
63  AV,
64  BV,
65  T,
66  NOT_MARK,
67  NUM_MARK_TYPES = NOT_MARK
68};
69
70static thai_mark_type_t
71get_mark_type (hb_codepoint_t u)
72{
73  if (u == 0x0E31u || hb_in_range (u, 0x0E34u, 0x0E37u) ||
74      u == 0x0E47u || hb_in_range (u, 0x0E4Du, 0x0E4Eu))
75    return AV;
76  if (hb_in_range (u, 0x0E38u, 0x0E3Au))
77    return BV;
78  if (hb_in_range (u, 0x0E48u, 0x0E4Cu))
79    return T;
80  return NOT_MARK;
81}
82
83
84enum thai_action_t
85{
86  NOP,
87  SD,  /* Shift combining-mark down */
88  SL,  /* Shift combining-mark left */
89  SDL, /* Shift combining-mark down-left */
90  RD   /* Remove descender from base */
91};
92
93static hb_codepoint_t
94thai_pua_shape (hb_codepoint_t u, thai_action_t action, hb_font_t *font)
95{
96  struct thai_pua_mapping_t {
97    hb_codepoint_t u;
98    hb_codepoint_t win_pua;
99    hb_codepoint_t mac_pua;
100  } const *pua_mappings = NULL;
101  static const thai_pua_mapping_t SD_mappings[] = {
102    {0x0E48u, 0xF70Au, 0xF88Bu}, /* MAI EK */
103    {0x0E49u, 0xF70Bu, 0xF88Eu}, /* MAI THO */
104    {0x0E4Au, 0xF70Cu, 0xF891u}, /* MAI TRI */
105    {0x0E4Bu, 0xF70Du, 0xF894u}, /* MAI CHATTAWA */
106    {0x0E4Cu, 0xF70Eu, 0xF897u}, /* THANTHAKHAT */
107    {0x0E38u, 0xF718u, 0xF89Bu}, /* SARA U */
108    {0x0E39u, 0xF719u, 0xF89Cu}, /* SARA UU */
109    {0x0E3Au, 0xF71Au, 0xF89Du}, /* PHINTHU */
110    {0x0000u, 0x0000u, 0x0000u}
111  };
112  static const thai_pua_mapping_t SDL_mappings[] = {
113    {0x0E48u, 0xF705u, 0xF88Cu}, /* MAI EK */
114    {0x0E49u, 0xF706u, 0xF88Fu}, /* MAI THO */
115    {0x0E4Au, 0xF707u, 0xF892u}, /* MAI TRI */
116    {0x0E4Bu, 0xF708u, 0xF895u}, /* MAI CHATTAWA */
117    {0x0E4Cu, 0xF709u, 0xF898u}, /* THANTHAKHAT */
118    {0x0000u, 0x0000u, 0x0000u}
119  };
120  static const thai_pua_mapping_t SL_mappings[] = {
121    {0x0E48u, 0xF713u, 0xF88Au}, /* MAI EK */
122    {0x0E49u, 0xF714u, 0xF88Du}, /* MAI THO */
123    {0x0E4Au, 0xF715u, 0xF890u}, /* MAI TRI */
124    {0x0E4Bu, 0xF716u, 0xF893u}, /* MAI CHATTAWA */
125    {0x0E4Cu, 0xF717u, 0xF896u}, /* THANTHAKHAT */
126    {0x0E31u, 0xF710u, 0xF884u}, /* MAI HAN-AKAT */
127    {0x0E34u, 0xF701u, 0xF885u}, /* SARA I */
128    {0x0E35u, 0xF702u, 0xF886u}, /* SARA II */
129    {0x0E36u, 0xF703u, 0xF887u}, /* SARA UE */
130    {0x0E37u, 0xF704u, 0xF888u}, /* SARA UEE */
131    {0x0E47u, 0xF712u, 0xF889u}, /* MAITAIKHU */
132    {0x0E4Du, 0xF711u, 0xF899u}, /* NIKHAHIT */
133    {0x0000u, 0x0000u, 0x0000u}
134  };
135  static const thai_pua_mapping_t RD_mappings[] = {
136    {0x0E0Du, 0xF70Fu, 0xF89Au}, /* YO YING */
137    {0x0E10u, 0xF700u, 0xF89Eu}, /* THO THAN */
138    {0x0000u, 0x0000u, 0x0000u}
139  };
140
141  switch (action) {
142    default: assert (false); /* Fallthrough */
143    case NOP: return u;
144    case SD:  pua_mappings = SD_mappings; break;
145    case SDL: pua_mappings = SDL_mappings; break;
146    case SL:  pua_mappings = SL_mappings; break;
147    case RD:  pua_mappings = RD_mappings; break;
148  }
149  for (; pua_mappings->u; pua_mappings++)
150    if (pua_mappings->u == u)
151    {
152      hb_codepoint_t glyph;
153      if (hb_font_get_glyph (font, pua_mappings->win_pua, 0, &glyph))
154	return pua_mappings->win_pua;
155      if (hb_font_get_glyph (font, pua_mappings->mac_pua, 0, &glyph))
156	return pua_mappings->mac_pua;
157      break;
158    }
159  return u;
160}
161
162
163static enum thai_above_state_t
164{     /* Cluster above looks like: */
165  T0, /*  ⣤                      */
166  T1, /*     ⣼                   */
167  T2, /*        ⣾                */
168  T3, /*           ⣿             */
169  NUM_ABOVE_STATES
170} thai_above_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] =
171{
172  T0, /* NC */
173  T1, /* AC */
174  T0, /* RC */
175  T0, /* DC */
176  T3, /* NOT_CONSONANT */
177};
178
179static const struct thai_above_state_machine_edge_t {
180  thai_action_t action;
181  thai_above_state_t next_state;
182} thai_above_state_machine[NUM_ABOVE_STATES][NUM_MARK_TYPES] =
183{        /*AV*/    /*BV*/    /*T*/
184/*T0*/ {{NOP,T3}, {NOP,T0}, {SD, T3}},
185/*T1*/ {{SL, T2}, {NOP,T1}, {SDL,T2}},
186/*T2*/ {{NOP,T3}, {NOP,T2}, {SL, T3}},
187/*T3*/ {{NOP,T3}, {NOP,T3}, {NOP,T3}},
188};
189
190
191static enum thai_below_state_t
192{
193  B0, /* No descender */
194  B1, /* Removable descender */
195  B2, /* Strict descender */
196  NUM_BELOW_STATES
197} thai_below_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] =
198{
199  B0, /* NC */
200  B0, /* AC */
201  B1, /* RC */
202  B2, /* DC */
203  B2, /* NOT_CONSONANT */
204};
205
206static const struct thai_below_state_machine_edge_t {
207  thai_action_t action;
208  thai_below_state_t next_state;
209} thai_below_state_machine[NUM_BELOW_STATES][NUM_MARK_TYPES] =
210{        /*AV*/    /*BV*/    /*T*/
211/*B0*/ {{NOP,B0}, {NOP,B2}, {NOP, B0}},
212/*B1*/ {{NOP,B1}, {RD, B2}, {NOP, B1}},
213/*B2*/ {{NOP,B2}, {SD, B2}, {NOP, B2}},
214};
215
216
217static void
218do_thai_pua_shaping (const hb_ot_shape_plan_t *plan HB_UNUSED,
219		     hb_buffer_t              *buffer,
220		     hb_font_t                *font)
221{
222  thai_above_state_t above_state = thai_above_start_state[NOT_CONSONANT];
223  thai_below_state_t below_state = thai_below_start_state[NOT_CONSONANT];
224  unsigned int base = 0;
225
226  hb_glyph_info_t *info = buffer->info;
227  unsigned int count = buffer->len;
228  for (unsigned int i = 0; i < count; i++)
229  {
230    thai_mark_type_t mt = get_mark_type (info[i].codepoint);
231
232    if (mt == NOT_MARK) {
233      thai_consonant_type_t ct = get_consonant_type (info[i].codepoint);
234      above_state = thai_above_start_state[ct];
235      below_state = thai_below_start_state[ct];
236      base = i;
237      continue;
238    }
239
240    const thai_above_state_machine_edge_t &above_edge = thai_above_state_machine[above_state][mt];
241    const thai_below_state_machine_edge_t &below_edge = thai_below_state_machine[below_state][mt];
242    above_state = above_edge.next_state;
243    below_state = below_edge.next_state;
244
245    /* At least one of the above/below actions is NOP. */
246    thai_action_t action = above_edge.action != NOP ? above_edge.action : below_edge.action;
247
248    if (action == RD)
249      info[base].codepoint = thai_pua_shape (info[base].codepoint, action, font);
250    else
251      info[i].codepoint = thai_pua_shape (info[i].codepoint, action, font);
252  }
253}
254
255
256static void
257preprocess_text_thai (const hb_ot_shape_plan_t *plan,
258		      hb_buffer_t              *buffer,
259		      hb_font_t                *font)
260{
261  /* This function implements the shaping logic documented here:
262   *
263   *   http://linux.thai.net/~thep/th-otf/shaping.html
264   *
265   * The first shaping rule listed there is needed even if the font has Thai
266   * OpenType tables.  The rest do fallback positioning based on PUA codepoints.
267   * We implement that only if there exist no Thai GSUB in the font.
268   */
269
270  /* The following is NOT specified in the MS OT Thai spec, however, it seems
271   * to be what Uniscribe and other engines implement.  According to Eric Muller:
272   *
273   * When you have a SARA AM, decompose it in NIKHAHIT + SARA AA, *and* move the
274   * NIKHAHIT backwards over any tone mark (0E48-0E4B).
275   *
276   * <0E14, 0E4B, 0E33> -> <0E14, 0E4D, 0E4B, 0E32>
277   *
278   * This reordering is legit only when the NIKHAHIT comes from a SARA AM, not
279   * when it's there to start with. The string <0E14, 0E4B, 0E4D> is probably
280   * not what a user wanted, but the rendering is nevertheless nikhahit above
281   * chattawa.
282   *
283   * Same for Lao.
284   *
285   * Note:
286   *
287   * Uniscribe also does some below-marks reordering.  Namely, it positions U+0E3A
288   * after U+0E38 and U+0E39.  We do that by modifying the ccc for U+0E3A.
289   * See unicode->modified_combining_class ().  Lao does NOT have a U+0E3A
290   * equivalent.
291   */
292
293
294  /*
295   * Here are the characters of significance:
296   *
297   *			Thai	Lao
298   * SARA AM:		U+0E33	U+0EB3
299   * SARA AA:		U+0E32	U+0EB2
300   * Nikhahit:		U+0E4D	U+0ECD
301   *
302   * Testing shows that Uniscribe reorder the following marks:
303   * Thai:	<0E31,0E34..0E37,0E47..0E4E>
304   * Lao:	<0EB1,0EB4..0EB7,0EC7..0ECE>
305   *
306   * Note how the Lao versions are the same as Thai + 0x80.
307   */
308
309  /* We only get one script at a time, so a script-agnostic implementation
310   * is adequate here. */
311#define IS_SARA_AM(x) (((x) & ~0x0080u) == 0x0E33u)
312#define NIKHAHIT_FROM_SARA_AM(x) ((x) - 0x0E33u + 0x0E4Du)
313#define SARA_AA_FROM_SARA_AM(x) ((x) - 1)
314#define IS_TONE_MARK(x) (hb_in_ranges ((x) & ~0x0080u, 0x0E34u, 0x0E37u, 0x0E47u, 0x0E4Eu, 0x0E31u, 0x0E31u))
315
316  buffer->clear_output ();
317  unsigned int count = buffer->len;
318  for (buffer->idx = 0; buffer->idx < count;)
319  {
320    hb_codepoint_t u = buffer->cur().codepoint;
321    if (likely (!IS_SARA_AM (u))) {
322      buffer->next_glyph ();
323      continue;
324    }
325
326    /* Is SARA AM. Decompose and reorder. */
327    hb_codepoint_t decomposed[2] = {hb_codepoint_t (NIKHAHIT_FROM_SARA_AM (u)),
328				    hb_codepoint_t (SARA_AA_FROM_SARA_AM (u))};
329    buffer->replace_glyphs (1, 2, decomposed);
330    if (unlikely (buffer->in_error))
331      return;
332
333    /* Make Nikhahit be recognized as a mark when zeroing widths. */
334    unsigned int end = buffer->out_len;
335    _hb_glyph_info_set_general_category (&buffer->out_info[end - 2], HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK);
336
337    /* Ok, let's see... */
338    unsigned int start = end - 2;
339    while (start > 0 && IS_TONE_MARK (buffer->out_info[start - 1].codepoint))
340      start--;
341
342    if (start + 2 < end)
343    {
344      /* Move Nikhahit (end-2) to the beginning */
345      buffer->merge_out_clusters (start, end);
346      hb_glyph_info_t t = buffer->out_info[end - 2];
347      memmove (buffer->out_info + start + 1,
348	       buffer->out_info + start,
349	       sizeof (buffer->out_info[0]) * (end - start - 2));
350      buffer->out_info[start] = t;
351    }
352    else
353    {
354      /* Since we decomposed, and NIKHAHIT is combining, merge clusters with the
355       * previous cluster. */
356      if (start)
357	buffer->merge_out_clusters (start - 1, end);
358    }
359  }
360  buffer->swap_buffers ();
361
362  /* If font has Thai GSUB, we are done. */
363  if (plan->props.script == HB_SCRIPT_THAI && !plan->map.found_script[0])
364    do_thai_pua_shaping (plan, buffer, font);
365}
366
367const hb_ot_complex_shaper_t _hb_ot_complex_shaper_thai =
368{
369  "thai",
370  NULL, /* collect_features */
371  NULL, /* override_features */
372  NULL, /* data_create */
373  NULL, /* data_destroy */
374  preprocess_text_thai,
375  HB_OT_SHAPE_NORMALIZATION_MODE_DEFAULT,
376  NULL, /* decompose */
377  NULL, /* compose */
378  NULL, /* setup_masks */
379  HB_OT_SHAPE_ZERO_WIDTH_MARKS_DEFAULT,
380  false,/* fallback_position */
381};
382