text: /*
   * Copyright © 2010,2012  Google, Inc.
   *
   *  This is part of HarfBuzz, a text shaping library.
   *
   * Permission is hereby granted, without written agreement and without
   * license or royalty fees, to use, copy, modify, and distribute this
   * software and its documentation for any purpose, provided that the
   * above copyright notice and the following two paragraphs appear in
   * all copies of this software.
   *
   * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
   * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
   * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
   * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
   * DAMAGE.
   *
   * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
   * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
   * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
   * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
   *
   * Google Author(s): Behdad Esfahbod
   */
  
  #include "hb-ot-shape-complex-private.hh"
  
  
  /* Thai / Lao shaper */
  
  
  /* PUA shaping */
  
  
  enum thai_consonant_type_t
  {
    NC,
    AC,
    RC,
    DC,
    NOT_CONSONANT,
    NUM_CONSONANT_TYPES = NOT_CONSONANT
  };
  
  static thai_consonant_type_t
  get_consonant_type (hb_codepoint_t u)
  {
    if (u == 0x0E1Bu || u == 0x0E1Du || u == 0x0E1Fu/* || u == 0x0E2Cu*/)
      return AC;
    if (u == 0x0E0Du || u == 0x0E10u)
      return RC;
    if (u == 0x0E0Eu || u == 0x0E0Fu)
      return DC;
    if (hb_in_range (u, 0x0E01u, 0x0E2Eu))
      return NC;
    return NOT_CONSONANT;
  }
  
  
  enum thai_mark_type_t
  {
    AV,
    BV,
    T,
    NOT_MARK,
    NUM_MARK_TYPES = NOT_MARK
  };
  
  static thai_mark_type_t
  get_mark_type (hb_codepoint_t u)
  {
    if (u == 0x0E31u || hb_in_range (u, 0x0E34u, 0x0E37u) ||
        u == 0x0E47u || hb_in_range (u, 0x0E4Du, 0x0E4Eu))
      return AV;
    if (hb_in_range (u, 0x0E38u, 0x0E3Au))
      return BV;
    if (hb_in_range (u, 0x0E48u, 0x0E4Cu))
      return T;
    return NOT_MARK;
  }
  
  
  enum thai_action_t
  {
    NOP,
    SD,  /* Shift combining-mark down */
    SL,  /* Shift combining-mark left */
    SDL, /* Shift combining-mark down-left */
    RD   /* Remove descender from base */
  };
  
  static hb_codepoint_t
  thai_pua_shape (hb_codepoint_t u, thai_action_t action, hb_font_t *font)
  {
    struct thai_pua_mapping_t {
      hb_codepoint_t u;
      hb_codepoint_t win_pua;
      hb_codepoint_t mac_pua;
    } const *pua_mappings = NULL;
    static const thai_pua_mapping_t SD_mappings[] = {
      {0x0E48u, 0xF70Au, 0xF88Bu}, /* MAI EK */
      {0x0E49u, 0xF70Bu, 0xF88Eu}, /* MAI THO */
      {0x0E4Au, 0xF70Cu, 0xF891u}, /* MAI TRI */
      {0x0E4Bu, 0xF70Du, 0xF894u}, /* MAI CHATTAWA */
      {0x0E4Cu, 0xF70Eu, 0xF897u}, /* THANTHAKHAT */
      {0x0E38u, 0xF718u, 0xF89Bu}, /* SARA U */
      {0x0E39u, 0xF719u, 0xF89Cu}, /* SARA UU */
      {0x0E3Au, 0xF71Au, 0xF89Du}, /* PHINTHU */
      {0x0000u, 0x0000u, 0x0000u}
    };
    static const thai_pua_mapping_t SDL_mappings[] = {
      {0x0E48u, 0xF705u, 0xF88Cu}, /* MAI EK */
      {0x0E49u, 0xF706u, 0xF88Fu}, /* MAI THO */
      {0x0E4Au, 0xF707u, 0xF892u}, /* MAI TRI */
      {0x0E4Bu, 0xF708u, 0xF895u}, /* MAI CHATTAWA */
      {0x0E4Cu, 0xF709u, 0xF898u}, /* THANTHAKHAT */
      {0x0000u, 0x0000u, 0x0000u}
    };
    static const thai_pua_mapping_t SL_mappings[] = {
      {0x0E48u, 0xF713u, 0xF88Au}, /* MAI EK */
      {0x0E49u, 0xF714u, 0xF88Du}, /* MAI THO */
      {0x0E4Au, 0xF715u, 0xF890u}, /* MAI TRI */
      {0x0E4Bu, 0xF716u, 0xF893u}, /* MAI CHATTAWA */
      {0x0E4Cu, 0xF717u, 0xF896u}, /* THANTHAKHAT */
      {0x0E31u, 0xF710u, 0xF884u}, /* MAI HAN-AKAT */
      {0x0E34u, 0xF701u, 0xF885u}, /* SARA I */
      {0x0E35u, 0xF702u, 0xF886u}, /* SARA II */
      {0x0E36u, 0xF703u, 0xF887u}, /* SARA UE */
      {0x0E37u, 0xF704u, 0xF888u}, /* SARA UEE */
      {0x0E47u, 0xF712u, 0xF889u}, /* MAITAIKHU */
      {0x0E4Du, 0xF711u, 0xF899u}, /* NIKHAHIT */
      {0x0000u, 0x0000u, 0x0000u}
    };
    static const thai_pua_mapping_t RD_mappings[] = {
      {0x0E0Du, 0xF70Fu, 0xF89Au}, /* YO YING */
      {0x0E10u, 0xF700u, 0xF89Eu}, /* THO THAN */
      {0x0000u, 0x0000u, 0x0000u}
    };
  
    switch (action) {
      default: assert (false); /* Fallthrough */
      case NOP: return u;
      case SD:  pua_mappings = SD_mappings; break;
      case SDL: pua_mappings = SDL_mappings; break;
      case SL:  pua_mappings = SL_mappings; break;
      case RD:  pua_mappings = RD_mappings; break;
    }
    for (; pua_mappings->u; pua_mappings++)
      if (pua_mappings->u == u)
      {
        hb_codepoint_t glyph;
        if (hb_font_get_glyph (font, pua_mappings->win_pua, 0, &glyph))
  	return pua_mappings->win_pua;
        if (hb_font_get_glyph (font, pua_mappings->mac_pua, 0, &glyph))
  	return pua_mappings->mac_pua;
        break;
      }
    return u;
  }
  
  
  static enum thai_above_state_t
  {     /* Cluster above looks like: */
    T0, /*  ⣤                      */
    T1, /*     ⣼                   */
    T2, /*        ⣾                */
    T3, /*           ⣿             */
    NUM_ABOVE_STATES
  } thai_above_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] =
  {
    T0, /* NC */
    T1, /* AC */
    T0, /* RC */
    T0, /* DC */
    T3, /* NOT_CONSONANT */
  };
  
  static const struct thai_above_state_machine_edge_t {
    thai_action_t action;
    thai_above_state_t next_state;
  } thai_above_state_machine[NUM_ABOVE_STATES][NUM_MARK_TYPES] =
  {        /*AV*/    /*BV*/    /*T*/
  /*T0*/ {{NOP,T3}, {NOP,T0}, {SD, T3}},
  /*T1*/ {{SL, T2}, {NOP,T1}, {SDL,T2}},
  /*T2*/ {{NOP,T3}, {NOP,T2}, {SL, T3}},
  /*T3*/ {{NOP,T3}, {NOP,T3}, {NOP,T3}},
  };
  
  
  static enum thai_below_state_t
  {
    B0, /* No descender */
    B1, /* Removable descender */
    B2, /* Strict descender */
    NUM_BELOW_STATES
  } thai_below_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] =
  {
    B0, /* NC */
    B0, /* AC */
    B1, /* RC */
    B2, /* DC */
    B2, /* NOT_CONSONANT */
  };
  
  static const struct thai_below_state_machine_edge_t {
    thai_action_t action;
    thai_below_state_t next_state;
  } thai_below_state_machine[NUM_BELOW_STATES][NUM_MARK_TYPES] =
  {        /*AV*/    /*BV*/    /*T*/
  /*B0*/ {{NOP,B0}, {NOP,B2}, {NOP, B0}},
  /*B1*/ {{NOP,B1}, {RD, B2}, {NOP, B1}},
  /*B2*/ {{NOP,B2}, {SD, B2}, {NOP, B2}},
  };
  
  
  static void
  do_thai_pua_shaping (const hb_ot_shape_plan_t *plan HB_UNUSED,
  		     hb_buffer_t              *buffer,
  		     hb_font_t                *font)
  {
    thai_above_state_t above_state = thai_above_start_state[NOT_CONSONANT];
    thai_below_state_t below_state = thai_below_start_state[NOT_CONSONANT];
    unsigned int base = 0;
  
    hb_glyph_info_t *info = buffer->info;
    unsigned int count = buffer->len;
    for (unsigned int i = 0; i < count; i++)
    {
      thai_mark_type_t mt = get_mark_type (info[i].codepoint);
  
      if (mt == NOT_MARK) {
        thai_consonant_type_t ct = get_consonant_type (info[i].codepoint);
        above_state = thai_above_start_state[ct];
        below_state = thai_below_start_state[ct];
        base = i;
        continue;
      }
  
      const thai_above_state_machine_edge_t &above_edge = thai_above_state_machine[above_state][mt];
      const thai_below_state_machine_edge_t &below_edge = thai_below_state_machine[below_state][mt];
      above_state = above_edge.next_state;
      below_state = below_edge.next_state;
  
      /* At least one of the above/below actions is NOP. */
      thai_action_t action = above_edge.action != NOP ? above_edge.action : below_edge.action;
  
      if (action == RD)
        info[base].codepoint = thai_pua_shape (info[base].codepoint, action, font);
      else
        info[i].codepoint = thai_pua_shape (info[i].codepoint, action, font);
    }
  }
  
  
  static void
  preprocess_text_thai (const hb_ot_shape_plan_t *plan,
  		      hb_buffer_t              *buffer,
  		      hb_font_t                *font)
  {
    /* This function implements the shaping logic documented here:
     *
     *   http://linux.thai.net/~thep/th-otf/shaping.html
     *
     * The first shaping rule listed there is needed even if the font has Thai
     * OpenType tables.  The rest do fallback positioning based on PUA codepoints.
     * We implement that only if there exist no Thai GSUB in the font.
     */
  
    /* The following is NOT specified in the MS OT Thai spec, however, it seems
     * to be what Uniscribe and other engines implement.  According to Eric Muller:
     *
     * When you have a SARA AM, decompose it in NIKHAHIT + SARA AA, *and* move the
     * NIKHAHIT backwards over any tone mark (0E48-0E4B).
     *
     * <0E14, 0E4B, 0E33> -> <0E14, 0E4D, 0E4B, 0E32>
     *
     * This reordering is legit only when the NIKHAHIT comes from a SARA AM, not
     * when it's there to start with. The string <0E14, 0E4B, 0E4D> is probably
     * not what a user wanted, but the rendering is nevertheless nikhahit above
     * chattawa.
     *
     * Same for Lao.
     *
     * Note:
     *
     * Uniscribe also does some below-marks reordering.  Namely, it positions U+0E3A
     * after U+0E38 and U+0E39.  We do that by modifying the ccc for U+0E3A.
     * See unicode->modified_combining_class ().  Lao does NOT have a U+0E3A
     * equivalent.
     */
  
  
    /*
     * Here are the characters of significance:
     *
     *			Thai	Lao
     * SARA AM:		U+0E33	U+0EB3
     * SARA AA:		U+0E32	U+0EB2
     * Nikhahit:		U+0E4D	U+0ECD
     *
     * Testing shows that Uniscribe reorder the following marks:
     * Thai:	<0E31,0E34..0E37,0E47..0E4E>
     * Lao:	<0EB1,0EB4..0EB7,0EC7..0ECE>
     *
     * Note how the Lao versions are the same as Thai + 0x80.
     */
  
    /* We only get one script at a time, so a script-agnostic implementation
     * is adequate here. */
  #define IS_SARA_AM(x) (((x) & ~0x0080u) == 0x0E33u)
  #define NIKHAHIT_FROM_SARA_AM(x) ((x) - 0x0E33u + 0x0E4Du)
  #define SARA_AA_FROM_SARA_AM(x) ((x) - 1)
  #define IS_TONE_MARK(x) (hb_in_ranges ((x) & ~0x0080u, 0x0E34u, 0x0E37u, 0x0E47u, 0x0E4Eu, 0x0E31u, 0x0E31u))
  
    buffer->clear_output ();
    unsigned int count = buffer->len;
    for (buffer->idx = 0; buffer->idx < count;)
    {
      hb_codepoint_t u = buffer->cur().codepoint;
      if (likely (!IS_SARA_AM (u))) {
        buffer->next_glyph ();
        continue;
      }
  
      /* Is SARA AM. Decompose and reorder. */
      hb_codepoint_t decomposed[2] = {hb_codepoint_t (NIKHAHIT_FROM_SARA_AM (u)),
  				    hb_codepoint_t (SARA_AA_FROM_SARA_AM (u))};
      buffer->replace_glyphs (1, 2, decomposed);
      if (unlikely (buffer->in_error))
        return;
  
      /* Make Nikhahit be recognized as a mark when zeroing widths. */
      unsigned int end = buffer->out_len;
      _hb_glyph_info_set_general_category (&buffer->out_info[end - 2], HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK);
  
      /* Ok, let's see... */
      unsigned int start = end - 2;
      while (start > 0 && IS_TONE_MARK (buffer->out_info[start - 1].codepoint))
        start--;
  
      if (start + 2 < end)
      {
        /* Move Nikhahit (end-2) to the beginning */
        buffer->merge_out_clusters (start, end);
        hb_glyph_info_t t = buffer->out_info[end - 2];
        memmove (buffer->out_info + start + 1,
  	       buffer->out_info + start,
  	       sizeof (buffer->out_info[0]) * (end - start - 2));
        buffer->out_info[start] = t;
      }
      else
      {
        /* Since we decomposed, and NIKHAHIT is combining, merge clusters with the
         * previous cluster. */
        if (start && buffer->cluster_level == HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES)
  	buffer->merge_out_clusters (start - 1, end);
      }
    }
    buffer->swap_buffers ();
  
    /* If font has Thai GSUB, we are done. */
    if (plan->props.script == HB_SCRIPT_THAI && !plan->map.found_script[0])
      do_thai_pua_shaping (plan, buffer, font);
  }
  
  const hb_ot_complex_shaper_t _hb_ot_complex_shaper_thai =
  {
    "thai",
    NULL, /* collect_features */
    NULL, /* override_features */
    NULL, /* data_create */
    NULL, /* data_destroy */
    preprocess_text_thai,
    HB_OT_SHAPE_NORMALIZATION_MODE_DEFAULT,
    NULL, /* decompose */
    NULL, /* compose */
    NULL, /* setup_masks */
    HB_OT_SHAPE_ZERO_WIDTH_MARKS_DEFAULT,
    false,/* fallback_position */
  };
  