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 

    36 enum thai_consonant_type_t

    37 {

    38   NC,

    39   AC,

    40   RC,

    41   DC,

    42   NOT_CONSONANT,

    43   NUM_CONSONANT_TYPES = NOT_CONSONANT

    44 };

    45 

    46 static thai_consonant_type_t

    47 get_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 

    61 enum thai_mark_type_t

    62 {

    63   AV,

    64   BV,

    65   T,

    66   NOT_MARK,

    67   NUM_MARK_TYPES = NOT_MARK

    68 };

    69 

    70 static thai_mark_type_t

    71 get_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 

    84 enum 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 

    93 static hb_codepoint_t

    94 thai_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 

   163 static 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 

   179 static 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 

   191 static 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 

   206 static 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 

   217 static void

   218 do_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 

   256 static void

   257 preprocess_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 && buffer->cluster_level == HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES)

   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 

   367 const 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 };