text: /*
   * Copyright © 2011,2012  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-indic.hh"
  #include "hb-ot-layout.hh"
  
  
  /*
   * Indic shaper.
   */
  
  
  /*
   * Indic configurations.  Note that we do not want to keep every single script-specific
   * behavior in these tables necessarily.  This should mainly be used for per-script
   * properties that are cheaper keeping here, than in the code.  Ie. if, say, one and
   * only one script has an exception, that one script can be if'ed directly in the code,
   * instead of adding a new flag in these structs.
   */
  
  enum base_position_t {
    BASE_POS_LAST_SINHALA,
    BASE_POS_LAST
  };
  enum reph_position_t {
    REPH_POS_AFTER_MAIN  = POS_AFTER_MAIN,
    REPH_POS_BEFORE_SUB  = POS_BEFORE_SUB,
    REPH_POS_AFTER_SUB   = POS_AFTER_SUB,
    REPH_POS_BEFORE_POST = POS_BEFORE_POST,
    REPH_POS_AFTER_POST  = POS_AFTER_POST
  };
  enum reph_mode_t {
    REPH_MODE_IMPLICIT,  /* Reph formed out of initial Ra,H sequence. */
    REPH_MODE_EXPLICIT,  /* Reph formed out of initial Ra,H,ZWJ sequence. */
    REPH_MODE_LOG_REPHA  /* Encoded Repha character, needs reordering. */
  };
  enum blwf_mode_t {
    BLWF_MODE_PRE_AND_POST, /* Below-forms feature applied to pre-base and post-base. */
    BLWF_MODE_POST_ONLY     /* Below-forms feature applied to post-base only. */
  };
  struct indic_config_t
  {
    hb_script_t     script;
    bool            has_old_spec;
    hb_codepoint_t  virama;
    base_position_t base_pos;
    reph_position_t reph_pos;
    reph_mode_t     reph_mode;
    blwf_mode_t     blwf_mode;
  };
  
  static const indic_config_t indic_configs[] =
  {
    /* Default.  Should be first. */
    {HB_SCRIPT_INVALID,	false,      0,BASE_POS_LAST, REPH_POS_BEFORE_POST,REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
    {HB_SCRIPT_DEVANAGARI,true, 0x094Du,BASE_POS_LAST, REPH_POS_BEFORE_POST,REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
    {HB_SCRIPT_BENGALI,	true, 0x09CDu,BASE_POS_LAST, REPH_POS_AFTER_SUB,  REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
    {HB_SCRIPT_GURMUKHI,	true, 0x0A4Du,BASE_POS_LAST, REPH_POS_BEFORE_SUB, REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
    {HB_SCRIPT_GUJARATI,	true, 0x0ACDu,BASE_POS_LAST, REPH_POS_BEFORE_POST,REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
    {HB_SCRIPT_ORIYA,	true, 0x0B4Du,BASE_POS_LAST, REPH_POS_AFTER_MAIN, REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
    {HB_SCRIPT_TAMIL,	true, 0x0BCDu,BASE_POS_LAST, REPH_POS_AFTER_POST, REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
    {HB_SCRIPT_TELUGU,	true, 0x0C4Du,BASE_POS_LAST, REPH_POS_AFTER_POST, REPH_MODE_EXPLICIT, BLWF_MODE_POST_ONLY},
    {HB_SCRIPT_KANNADA,	true, 0x0CCDu,BASE_POS_LAST, REPH_POS_AFTER_POST, REPH_MODE_IMPLICIT, BLWF_MODE_POST_ONLY},
    {HB_SCRIPT_MALAYALAM,	true, 0x0D4Du,BASE_POS_LAST, REPH_POS_AFTER_MAIN, REPH_MODE_LOG_REPHA,BLWF_MODE_PRE_AND_POST},
    {HB_SCRIPT_SINHALA,	false,0x0DCAu,BASE_POS_LAST_SINHALA,
  						     REPH_POS_AFTER_POST, REPH_MODE_EXPLICIT, BLWF_MODE_PRE_AND_POST},
  };
  
  
  
  /*
   * Indic shaper.
   */
  
  struct feature_list_t {
    hb_tag_t tag;
    hb_ot_map_feature_flags_t flags;
  };
  
  static const feature_list_t
  indic_features[] =
  {
    /*
     * Basic features.
     * These features are applied in order, one at a time, after initial_reordering.
     */
    {HB_TAG('n','u','k','t'), F_GLOBAL},
    {HB_TAG('a','k','h','n'), F_GLOBAL},
    {HB_TAG('r','p','h','f'), F_NONE},
    {HB_TAG('r','k','r','f'), F_GLOBAL},
    {HB_TAG('p','r','e','f'), F_NONE},
    {HB_TAG('b','l','w','f'), F_NONE},
    {HB_TAG('a','b','v','f'), F_NONE},
    {HB_TAG('h','a','l','f'), F_NONE},
    {HB_TAG('p','s','t','f'), F_NONE},
    {HB_TAG('v','a','t','u'), F_GLOBAL},
    {HB_TAG('c','j','c','t'), F_GLOBAL},
    /*
     * Other features.
     * These features are applied all at once, after final_reordering.
     * Default Bengali font in Windows for example has intermixed
     * lookups for init,pres,abvs,blws features.
     */
    {HB_TAG('i','n','i','t'), F_NONE},
    {HB_TAG('p','r','e','s'), F_GLOBAL},
    {HB_TAG('a','b','v','s'), F_GLOBAL},
    {HB_TAG('b','l','w','s'), F_GLOBAL},
    {HB_TAG('p','s','t','s'), F_GLOBAL},
    {HB_TAG('h','a','l','n'), F_GLOBAL},
    /* Positioning features, though we don't care about the types. */
    {HB_TAG('d','i','s','t'), F_GLOBAL},
    {HB_TAG('a','b','v','m'), F_GLOBAL},
    {HB_TAG('b','l','w','m'), F_GLOBAL},
  };
  
  /*
   * Must be in the same order as the indic_features array.
   */
  enum {
    _NUKT,
    _AKHN,
    RPHF,
    _RKRF,
    PREF,
    BLWF,
    ABVF,
    HALF,
    PSTF,
    _VATU,
    _CJCT,
  
    INIT,
    _PRES,
    _ABVS,
    _BLWS,
    _PSTS,
    _HALN,
    _DIST,
    _ABVM,
    _BLWM,
  
    INDIC_NUM_FEATURES,
    INDIC_BASIC_FEATURES = INIT /* Don't forget to update this! */
  };
  
  static void
  setup_syllables (const hb_ot_shape_plan_t *plan,
  		 hb_font_t *font,
  		 hb_buffer_t *buffer);
  static void
  initial_reordering (const hb_ot_shape_plan_t *plan,
  		    hb_font_t *font,
  		    hb_buffer_t *buffer);
  static void
  final_reordering (const hb_ot_shape_plan_t *plan,
  		  hb_font_t *font,
  		  hb_buffer_t *buffer);
  static void
  clear_syllables (const hb_ot_shape_plan_t *plan,
  		 hb_font_t *font,
  		 hb_buffer_t *buffer);
  
  static void
  collect_features_indic (hb_ot_shape_planner_t *plan)
  {
    hb_ot_map_builder_t *map = &plan->map;
  
    /* Do this before any lookups have been applied. */
    map->add_gsub_pause (setup_syllables);
  
    map->add_global_bool_feature (HB_TAG('l','o','c','l'));
    /* The Indic specs do not require ccmp, but we apply it here since if
     * there is a use of it, it's typically at the beginning. */
    map->add_global_bool_feature (HB_TAG('c','c','m','p'));
  
  
    unsigned int i = 0;
    map->add_gsub_pause (initial_reordering);
    for (; i < INDIC_BASIC_FEATURES; i++) {
      map->add_feature (indic_features[i].tag, 1, indic_features[i].flags | F_MANUAL_ZWJ | F_MANUAL_ZWNJ);
      map->add_gsub_pause (nullptr);
    }
    map->add_gsub_pause (final_reordering);
    for (; i < INDIC_NUM_FEATURES; i++) {
      map->add_feature (indic_features[i].tag, 1, indic_features[i].flags | F_MANUAL_ZWJ | F_MANUAL_ZWNJ);
    }
  
    map->add_global_bool_feature (HB_TAG('c','a','l','t'));
    map->add_global_bool_feature (HB_TAG('c','l','i','g'));
  
    map->add_gsub_pause (clear_syllables);
  }
  
  static void
  override_features_indic (hb_ot_shape_planner_t *plan)
  {
    plan->map.add_feature (HB_TAG('l','i','g','a'), 0, F_GLOBAL);
  }
  
  
  struct would_substitute_feature_t
  {
    inline void init (const hb_ot_map_t *map, hb_tag_t feature_tag, bool zero_context_)
    {
      zero_context = zero_context_;
      map->get_stage_lookups (0/*GSUB*/,
  			    map->get_feature_stage (0/*GSUB*/, feature_tag),
  			    &lookups, &count);
    }
  
    inline bool would_substitute (const hb_codepoint_t *glyphs,
  				unsigned int          glyphs_count,
  				hb_face_t            *face) const
    {
      for (unsigned int i = 0; i < count; i++)
        if (hb_ot_layout_lookup_would_substitute_fast (face, lookups[i].index, glyphs, glyphs_count, zero_context))
  	return true;
      return false;
    }
  
    private:
    const hb_ot_map_t::lookup_map_t *lookups;
    unsigned int count;
    bool zero_context;
  };
  
  struct indic_shape_plan_t
  {
    ASSERT_POD ();
  
    inline bool load_virama_glyph (hb_font_t *font, hb_codepoint_t *pglyph) const
    {
      hb_codepoint_t glyph = virama_glyph.get_relaxed ();
      if (unlikely (glyph == (hb_codepoint_t) -1))
      {
        if (!config->virama || !font->get_nominal_glyph (config->virama, &glyph))
  	glyph = 0;
        /* Technically speaking, the spec says we should apply 'locl' to virama too.
         * Maybe one day... */
  
        /* Our get_nominal_glyph() function needs a font, so we can't get the virama glyph
         * during shape planning...  Instead, overwrite it here. */
        virama_glyph.set_relaxed ((int) glyph);
      }
  
      *pglyph = glyph;
      return glyph != 0;
    }
  
    const indic_config_t *config;
  
    bool is_old_spec;
    mutable hb_atomic_int_t virama_glyph;
  
    would_substitute_feature_t rphf;
    would_substitute_feature_t pref;
    would_substitute_feature_t blwf;
    would_substitute_feature_t pstf;
  
    hb_mask_t mask_array[INDIC_NUM_FEATURES];
  };
  
  static void *
  data_create_indic (const hb_ot_shape_plan_t *plan)
  {
    indic_shape_plan_t *indic_plan = (indic_shape_plan_t *) calloc (1, sizeof (indic_shape_plan_t));
    if (unlikely (!indic_plan))
      return nullptr;
  
    indic_plan->config = &indic_configs[0];
    for (unsigned int i = 1; i < ARRAY_LENGTH (indic_configs); i++)
      if (plan->props.script == indic_configs[i].script) {
        indic_plan->config = &indic_configs[i];
        break;
      }
  
    indic_plan->is_old_spec = indic_plan->config->has_old_spec && ((plan->map.chosen_script[0] & 0x000000FFu) != '2');
    indic_plan->virama_glyph.set_relaxed (-1);
  
    /* Use zero-context would_substitute() matching for new-spec of the main
     * Indic scripts, and scripts with one spec only, but not for old-specs.
     * The new-spec for all dual-spec scripts says zero-context matching happens.
     *
     * However, testing with Malayalam shows that old and new spec both allow
     * context.  Testing with Bengali new-spec however shows that it doesn't.
     * So, the heuristic here is the way it is.  It should *only* be changed,
     * as we discover more cases of what Windows does.  DON'T TOUCH OTHERWISE.
     */
    bool zero_context = !indic_plan->is_old_spec && plan->props.script != HB_SCRIPT_MALAYALAM;
    indic_plan->rphf.init (&plan->map, HB_TAG('r','p','h','f'), zero_context);
    indic_plan->pref.init (&plan->map, HB_TAG('p','r','e','f'), zero_context);
    indic_plan->blwf.init (&plan->map, HB_TAG('b','l','w','f'), zero_context);
    indic_plan->pstf.init (&plan->map, HB_TAG('p','s','t','f'), zero_context);
  
    for (unsigned int i = 0; i < ARRAY_LENGTH (indic_plan->mask_array); i++)
      indic_plan->mask_array[i] = (indic_features[i].flags & F_GLOBAL) ?
  				 0 : plan->map.get_1_mask (indic_features[i].tag);
  
    return indic_plan;
  }
  
  static void
  data_destroy_indic (void *data)
  {
    free (data);
  }
  
  static indic_position_t
  consonant_position_from_face (const indic_shape_plan_t *indic_plan,
  			      const hb_codepoint_t consonant,
  			      const hb_codepoint_t virama,
  			      hb_face_t *face)
  {
    /* For old-spec, the order of glyphs is Consonant,Virama,
     * whereas for new-spec, it's Virama,Consonant.  However,
     * some broken fonts (like Free Sans) simply copied lookups
     * from old-spec to new-spec without modification.
     * And oddly enough, Uniscribe seems to respect those lookups.
     * Eg. in the sequence U+0924,U+094D,U+0930, Uniscribe finds
     * base at 0.  The font however, only has lookups matching
     * 930,94D in 'blwf', not the expected 94D,930 (with new-spec
     * table).  As such, we simply match both sequences.  Seems
     * to work. */
    hb_codepoint_t glyphs[3] = {virama, consonant, virama};
    if (indic_plan->blwf.would_substitute (glyphs  , 2, face) ||
        indic_plan->blwf.would_substitute (glyphs+1, 2, face))
      return POS_BELOW_C;
    if (indic_plan->pstf.would_substitute (glyphs  , 2, face) ||
        indic_plan->pstf.would_substitute (glyphs+1, 2, face))
      return POS_POST_C;
    if (indic_plan->pref.would_substitute (glyphs  , 2, face) ||
        indic_plan->pref.would_substitute (glyphs+1, 2, face))
      return POS_POST_C;
    return POS_BASE_C;
  }
  
  
  enum syllable_type_t {
    consonant_syllable,
    vowel_syllable,
    standalone_cluster,
    symbol_cluster,
    broken_cluster,
    non_indic_cluster,
  };
  
  #include "hb-ot-shape-complex-indic-machine.hh"
  
  
  static void
  setup_masks_indic (const hb_ot_shape_plan_t *plan HB_UNUSED,
  		   hb_buffer_t              *buffer,
  		   hb_font_t                *font HB_UNUSED)
  {
    HB_BUFFER_ALLOCATE_VAR (buffer, indic_category);
    HB_BUFFER_ALLOCATE_VAR (buffer, indic_position);
  
    /* We cannot setup masks here.  We save information about characters
     * and setup masks later on in a pause-callback. */
  
    unsigned int count = buffer->len;
    hb_glyph_info_t *info = buffer->info;
    for (unsigned int i = 0; i < count; i++)
      set_indic_properties (info[i]);
  }
  
  static void
  setup_syllables (const hb_ot_shape_plan_t *plan HB_UNUSED,
  		 hb_font_t *font HB_UNUSED,
  		 hb_buffer_t *buffer)
  {
    find_syllables (buffer);
    foreach_syllable (buffer, start, end)
      buffer->unsafe_to_break (start, end);
  }
  
  static int
  compare_indic_order (const hb_glyph_info_t *pa, const hb_glyph_info_t *pb)
  {
    int a = pa->indic_position();
    int b = pb->indic_position();
  
    return a < b ? -1 : a == b ? 0 : +1;
  }
  
  
  
  static void
  update_consonant_positions (const hb_ot_shape_plan_t *plan,
  			    hb_font_t         *font,
  			    hb_buffer_t       *buffer)
  {
    const indic_shape_plan_t *indic_plan = (const indic_shape_plan_t *) plan->data;
  
    if (indic_plan->config->base_pos != BASE_POS_LAST)
      return;
  
    hb_codepoint_t virama;
    if (indic_plan->load_virama_glyph (font, &virama))
    {
      hb_face_t *face = font->face;
      unsigned int count = buffer->len;
      hb_glyph_info_t *info = buffer->info;
      for (unsigned int i = 0; i < count; i++)
        if (info[i].indic_position() == POS_BASE_C)
        {
  	hb_codepoint_t consonant = info[i].codepoint;
  	info[i].indic_position() = consonant_position_from_face (indic_plan, consonant, virama, face);
        }
    }
  }
  
  
  /* Rules from:
   * https://docs.microsqoft.com/en-us/typography/script-development/devanagari */
  
  static void
  initial_reordering_consonant_syllable (const hb_ot_shape_plan_t *plan,
  				       hb_face_t *face,
  				       hb_buffer_t *buffer,
  				       unsigned int start, unsigned int end)
  {
    const indic_shape_plan_t *indic_plan = (const indic_shape_plan_t *) plan->data;
    hb_glyph_info_t *info = buffer->info;
  
    /* https://github.com/harfbuzz/harfbuzz/issues/435#issuecomment-335560167
     * // For compatibility with legacy usage in Kannada,
     * // Ra+h+ZWJ must behave like Ra+ZWJ+h...
     */
    if (buffer->props.script == HB_SCRIPT_KANNADA &&
        start + 3 <= end &&
        is_one_of (info[start  ], FLAG (OT_Ra)) &&
        is_one_of (info[start+1], FLAG (OT_H)) &&
        is_one_of (info[start+2], FLAG (OT_ZWJ)))
    {
      buffer->merge_clusters (start+1, start+3);
      hb_glyph_info_t tmp = info[start+1];
      info[start+1] = info[start+2];
      info[start+2] = tmp;
    }
  
    /* 1. Find base consonant:
     *
     * The shaping engine finds the base consonant of the syllable, using the
     * following algorithm: starting from the end of the syllable, move backwards
     * until a consonant is found that does not have a below-base or post-base
     * form (post-base forms have to follow below-base forms), or that is not a
     * pre-base-reordering Ra, or arrive at the first consonant. The consonant
     * stopped at will be the base.
     *
     *   o If the syllable starts with Ra + Halant (in a script that has Reph)
     *     and has more than one consonant, Ra is excluded from candidates for
     *     base consonants.
     */
  
    unsigned int base = end;
    bool has_reph = false;
  
    {
      /* -> If the syllable starts with Ra + Halant (in a script that has Reph)
       *    and has more than one consonant, Ra is excluded from candidates for
       *    base consonants. */
      unsigned int limit = start;
      if (indic_plan->mask_array[RPHF] &&
  	start + 3 <= end &&
  	(
  	 (indic_plan->config->reph_mode == REPH_MODE_IMPLICIT && !is_joiner (info[start + 2])) ||
  	 (indic_plan->config->reph_mode == REPH_MODE_EXPLICIT && info[start + 2].indic_category() == OT_ZWJ)
  	))
      {
        /* See if it matches the 'rphf' feature. */
        hb_codepoint_t glyphs[3] = {info[start].codepoint,
  				  info[start + 1].codepoint,
  				  indic_plan->config->reph_mode == REPH_MODE_EXPLICIT ?
  				    info[start + 2].codepoint : 0};
        if (indic_plan->rphf.would_substitute (glyphs, 2, face) ||
  	  (indic_plan->config->reph_mode == REPH_MODE_EXPLICIT &&
  	   indic_plan->rphf.would_substitute (glyphs, 3, face)))
        {
  	limit += 2;
  	while (limit < end && is_joiner (info[limit]))
  	  limit++;
  	base = start;
  	has_reph = true;
        }
      } else if (indic_plan->config->reph_mode == REPH_MODE_LOG_REPHA && info[start].indic_category() == OT_Repha)
      {
  	limit += 1;
  	while (limit < end && is_joiner (info[limit]))
  	  limit++;
  	base = start;
  	has_reph = true;
      }
  
      switch (indic_plan->config->base_pos)
      {
        case BASE_POS_LAST:
        {
  	/* -> starting from the end of the syllable, move backwards */
  	unsigned int i = end;
  	bool seen_below = false;
  	do {
  	  i--;
  	  /* -> until a consonant is found */
  	  if (is_consonant (info[i]))
  	  {
  	    /* -> that does not have a below-base or post-base form
  	     * (post-base forms have to follow below-base forms), */
  	    if (info[i].indic_position() != POS_BELOW_C &&
  		(info[i].indic_position() != POS_POST_C || seen_below))
  	    {
  	      base = i;
  	      break;
  	    }
  	    if (info[i].indic_position() == POS_BELOW_C)
  	      seen_below = true;
  
  	    /* -> or that is not a pre-base-reordering Ra,
  	     *
  	     * IMPLEMENTATION NOTES:
  	     *
  	     * Our pre-base-reordering Ra's are marked POS_POST_C, so will be skipped
  	     * by the logic above already.
  	     */
  
  	    /* -> or arrive at the first consonant. The consonant stopped at will
  	     * be the base. */
  	    base = i;
  	  }
  	  else
  	  {
  	    /* A ZWJ after a Halant stops the base search, and requests an explicit
  	     * half form.
  	     * A ZWJ before a Halant, requests a subjoined form instead, and hence
  	     * search continues.  This is particularly important for Bengali
  	     * sequence Ra,H,Ya that should form Ya-Phalaa by subjoining Ya. */
  	    if (start < i &&
  		info[i].indic_category() == OT_ZWJ &&
  		info[i - 1].indic_category() == OT_H)
  	      break;
  	  }
  	} while (i > limit);
        }
        break;
  
        case BASE_POS_LAST_SINHALA:
        {
          /* Sinhala base positioning is slightly different from main Indic, in that:
  	 * 1. Its ZWJ behavior is different,
  	 * 2. We don't need to look into the font for consonant positions.
  	 */
  
  	if (!has_reph)
  	  base = limit;
  
  	/* Find the last base consonant that is not blocked by ZWJ.  If there is
  	 * a ZWJ right before a base consonant, that would request a subjoined form. */
  	for (unsigned int i = limit; i < end; i++)
  	  if (is_consonant (info[i]))
  	  {
  	    if (limit < i && info[i - 1].indic_category() == OT_ZWJ)
  	      break;
  	    else
  	      base = i;
  	  }
  
  	/* Mark all subsequent consonants as below. */
  	for (unsigned int i = base + 1; i < end; i++)
  	  if (is_consonant (info[i]))
  	    info[i].indic_position() = POS_BELOW_C;
        }
        break;
      }
  
      /* -> If the syllable starts with Ra + Halant (in a script that has Reph)
       *    and has more than one consonant, Ra is excluded from candidates for
       *    base consonants.
       *
       *  Only do this for unforced Reph. (ie. not for Ra,H,ZWJ. */
      if (has_reph && base == start && limit - base <= 2) {
        /* Have no other consonant, so Reph is not formed and Ra becomes base. */
        has_reph = false;
      }
    }
  
  
    /* 2. Decompose and reorder Matras:
     *
     * Each matra and any syllable modifier sign in the syllable are moved to the
     * appropriate position relative to the consonant(s) in the syllable. The
     * shaping engine decomposes two- or three-part matras into their constituent
     * parts before any repositioning. Matra characters are classified by which
     * consonant in a conjunct they have affinity for and are reordered to the
     * following positions:
     *
     *   o Before first half form in the syllable
     *   o After subjoined consonants
     *   o After post-form consonant
     *   o After main consonant (for above marks)
     *
     * IMPLEMENTATION NOTES:
     *
     * The normalize() routine has already decomposed matras for us, so we don't
     * need to worry about that.
     */
  
  
    /* 3.  Reorder marks to canonical order:
     *
     * Adjacent nukta and halant or nukta and vedic sign are always repositioned
     * if necessary, so that the nukta is first.
     *
     * IMPLEMENTATION NOTES:
     *
     * We don't need to do this: the normalize() routine already did this for us.
     */
  
  
    /* Reorder characters */
  
    for (unsigned int i = start; i < base; i++)
      info[i].indic_position() = MIN (POS_PRE_C, (indic_position_t) info[i].indic_position());
  
    if (base < end)
      info[base].indic_position() = POS_BASE_C;
  
    /* Mark final consonants.  A final consonant is one appearing after a matra.
     * Happens in Sinhala. */
    for (unsigned int i = base + 1; i < end; i++)
      if (info[i].indic_category() == OT_M) {
        for (unsigned int j = i + 1; j < end; j++)
  	if (is_consonant (info[j])) {
  	 info[j].indic_position() = POS_FINAL_C;
  	 break;
         }
        break;
      }
  
    /* Handle beginning Ra */
    if (has_reph)
      info[start].indic_position() = POS_RA_TO_BECOME_REPH;
  
    /* For old-style Indic script tags, move the first post-base Halant after
     * last consonant.
     *
     * Reports suggest that in some scripts Uniscribe does this only if there
     * is *not* a Halant after last consonant already.  We know that is the
     * case for Kannada, while it reorders unconditionally in other scripts,
     * eg. Malayalam, Bengali, and Devanagari.  We don't currently know about
     * other scripts, so we blacklist Kannada.
     *
     * Kannada test case:
     * U+0C9A,U+0CCD,U+0C9A,U+0CCD
     * With some versions of Lohit Kannada.
     * https://bugs.freedesktop.org/show_bug.cgi?id=59118
     *
     * Malayalam test case:
     * U+0D38,U+0D4D,U+0D31,U+0D4D,U+0D31,U+0D4D
     * With lohit-ttf-20121122/Lohit-Malayalam.ttf
     *
     * Bengali test case:
     * U+0998,U+09CD,U+09AF,U+09CD
     * With Windows XP vrinda.ttf
     * https://github.com/harfbuzz/harfbuzz/issues/1073
     *
     * Devanagari test case:
     * U+091F,U+094D,U+0930,U+094D
     * With chandas.ttf
     * https://github.com/harfbuzz/harfbuzz/issues/1071
     */
    if (indic_plan->is_old_spec)
    {
      bool disallow_double_halants = buffer->props.script == HB_SCRIPT_KANNADA;
      for (unsigned int i = base + 1; i < end; i++)
        if (info[i].indic_category() == OT_H)
        {
          unsigned int j;
          for (j = end - 1; j > i; j--)
  	  if (is_consonant (info[j]) ||
  	      (disallow_double_halants && info[j].indic_category() == OT_H))
  	    break;
  	if (info[j].indic_category() != OT_H && j > i) {
  	  /* Move Halant to after last consonant. */
  	  hb_glyph_info_t t = info[i];
  	  memmove (&info[i], &info[i + 1], (j - i) * sizeof (info[0]));
  	  info[j] = t;
  	}
          break;
        }
    }
  
    /* Attach misc marks to previous char to move with them. */
    {
      indic_position_t last_pos = POS_START;
      for (unsigned int i = start; i < end; i++)
      {
        if ((FLAG_UNSAFE (info[i].indic_category()) & (JOINER_FLAGS | FLAG (OT_N) | FLAG (OT_RS) | MEDIAL_FLAGS | FLAG (OT_H))))
        {
  	info[i].indic_position() = last_pos;
  	if (unlikely (info[i].indic_category() == OT_H &&
  		      info[i].indic_position() == POS_PRE_M))
  	{
  	  /*
  	   * Uniscribe doesn't move the Halant with Left Matra.
  	   * TEST: U+092B,U+093F,U+094DE
  	   * We follow.  This is important for the Sinhala
  	   * U+0DDA split matra since it decomposes to U+0DD9,U+0DCA
  	   * where U+0DD9 is a left matra and U+0DCA is the virama.
  	   * We don't want to move the virama with the left matra.
  	   * TEST: U+0D9A,U+0DDA
  	   */
  	  for (unsigned int j = i; j > start; j--)
  	    if (info[j - 1].indic_position() != POS_PRE_M) {
  	      info[i].indic_position() = info[j - 1].indic_position();
  	      break;
  	    }
  	}
        } else if (info[i].indic_position() != POS_SMVD) {
          last_pos = (indic_position_t) info[i].indic_position();
        }
      }
    }
    /* For post-base consonants let them own anything before them
     * since the last consonant or matra. */
    {
      unsigned int last = base;
      for (unsigned int i = base + 1; i < end; i++)
        if (is_consonant (info[i]))
        {
  	for (unsigned int j = last + 1; j < i; j++)
  	  if (info[j].indic_position() < POS_SMVD)
  	    info[j].indic_position() = info[i].indic_position();
  	last = i;
        } else if (info[i].indic_category() == OT_M)
          last = i;
    }
  
  
    {
      /* Use syllable() for sort accounting temporarily. */
      unsigned int syllable = info[start].syllable();
      for (unsigned int i = start; i < end; i++)
        info[i].syllable() = i - start;
  
      /* Sit tight, rock 'n roll! */
      hb_stable_sort (info + start, end - start, compare_indic_order);
      /* Find base again */
      base = end;
      for (unsigned int i = start; i < end; i++)
        if (info[i].indic_position() == POS_BASE_C)
        {
  	base = i;
  	break;
        }
      /* Things are out-of-control for post base positions, they may shuffle
       * around like crazy.  In old-spec mode, we move halants around, so in
       * that case merge all clusters after base.  Otherwise, check the sort
       * order and merge as needed.
       * For pre-base stuff, we handle cluster issues in final reordering.
       *
       * We could use buffer->sort() for this, if there was no special
       * reordering of pre-base stuff happening later...
       */
      if (indic_plan->is_old_spec || end - base > 127)
        buffer->merge_clusters (base, end);
      else
      {
        /* Note!  syllable() is a one-byte field. */
        for (unsigned int i = base; i < end; i++)
          if (info[i].syllable() != 255)
  	{
  	  unsigned int max = i;
  	  unsigned int j = start + info[i].syllable();
  	  while (j != i)
  	  {
  	    max = MAX (max, j);
  	    unsigned int next = start + info[j].syllable();
  	    info[j].syllable() = 255; /* So we don't process j later again. */
  	    j = next;
  	  }
  	  if (i != max)
  	    buffer->merge_clusters (i, max + 1);
  	}
      }
  
      /* Put syllable back in. */
      for (unsigned int i = start; i < end; i++)
        info[i].syllable() = syllable;
    }
  
    /* Setup masks now */
  
    {
      hb_mask_t mask;
  
      /* Reph */
      for (unsigned int i = start; i < end && info[i].indic_position() == POS_RA_TO_BECOME_REPH; i++)
        info[i].mask |= indic_plan->mask_array[RPHF];
  
      /* Pre-base */
      mask = indic_plan->mask_array[HALF];
      if (!indic_plan->is_old_spec &&
  	indic_plan->config->blwf_mode == BLWF_MODE_PRE_AND_POST)
        mask |= indic_plan->mask_array[BLWF];
      for (unsigned int i = start; i < base; i++)
        info[i].mask  |= mask;
      /* Base */
      mask = 0;
      if (base < end)
        info[base].mask |= mask;
      /* Post-base */
      mask = indic_plan->mask_array[BLWF] | indic_plan->mask_array[ABVF] | indic_plan->mask_array[PSTF];
      for (unsigned int i = base + 1; i < end; i++)
        info[i].mask  |= mask;
    }
  
    if (indic_plan->is_old_spec &&
        buffer->props.script == HB_SCRIPT_DEVANAGARI)
    {
      /* Old-spec eye-lash Ra needs special handling.  From the
       * spec:
       *
       * "The feature 'below-base form' is applied to consonants
       * having below-base forms and following the base consonant.
       * The exception is vattu, which may appear below half forms
       * as well as below the base glyph. The feature 'below-base
       * form' will be applied to all such occurrences of Ra as well."
       *
       * Test case: U+0924,U+094D,U+0930,U+094d,U+0915
       * with Sanskrit 2003 font.
       *
       * However, note that Ra,Halant,ZWJ is the correct way to
       * request eyelash form of Ra, so we wouldbn't inhibit it
       * in that sequence.
       *
       * Test case: U+0924,U+094D,U+0930,U+094d,U+200D,U+0915
       */
      for (unsigned int i = start; i + 1 < base; i++)
        if (info[i  ].indic_category() == OT_Ra &&
  	  info[i+1].indic_category() == OT_H  &&
  	  (i + 2 == base ||
  	   info[i+2].indic_category() != OT_ZWJ))
        {
  	info[i  ].mask |= indic_plan->mask_array[BLWF];
  	info[i+1].mask |= indic_plan->mask_array[BLWF];
        }
    }
  
    unsigned int pref_len = 2;
    if (indic_plan->mask_array[PREF] && base + pref_len < end)
    {
      /* Find a Halant,Ra sequence and mark it for pre-base-reordering processing. */
      for (unsigned int i = base + 1; i + pref_len - 1 < end; i++) {
        hb_codepoint_t glyphs[2];
        for (unsigned int j = 0; j < pref_len; j++)
          glyphs[j] = info[i + j].codepoint;
        if (indic_plan->pref.would_substitute (glyphs, pref_len, face))
        {
  	for (unsigned int j = 0; j < pref_len; j++)
  	  info[i++].mask |= indic_plan->mask_array[PREF];
  	break;
        }
      }
    }
  
    /* Apply ZWJ/ZWNJ effects */
    for (unsigned int i = start + 1; i < end; i++)
      if (is_joiner (info[i])) {
        bool non_joiner = info[i].indic_category() == OT_ZWNJ;
        unsigned int j = i;
  
        do {
  	j--;
  
  	/* ZWJ/ZWNJ should disable CJCT.  They do that by simply
  	 * being there, since we don't skip them for the CJCT
  	 * feature (ie. F_MANUAL_ZWJ) */
  
  	/* A ZWNJ disables HALF. */
  	if (non_joiner)
  	  info[j].mask &= ~indic_plan->mask_array[HALF];
  
        } while (j > start && !is_consonant (info[j]));
      }
  }
  
  static void
  initial_reordering_standalone_cluster (const hb_ot_shape_plan_t *plan,
  				       hb_face_t *face,
  				       hb_buffer_t *buffer,
  				       unsigned int start, unsigned int end)
  {
    /* We treat placeholder/dotted-circle as if they are consonants, so we
     * should just chain.  Only if not in compatibility mode that is... */
  
    if (hb_options ().uniscribe_bug_compatible)
    {
      /* For dotted-circle, this is what Uniscribe does:
       * If dotted-circle is the last glyph, it just does nothing.
       * Ie. It doesn't form Reph. */
      if (buffer->info[end - 1].indic_category() == OT_DOTTEDCIRCLE)
        return;
    }
  
    initial_reordering_consonant_syllable (plan, face, buffer, start, end);
  }
  
  static void
  initial_reordering_syllable (const hb_ot_shape_plan_t *plan,
  			     hb_face_t *face,
  			     hb_buffer_t *buffer,
  			     unsigned int start, unsigned int end)
  {
    syllable_type_t syllable_type = (syllable_type_t) (buffer->info[start].syllable() & 0x0F);
    switch (syllable_type)
    {
      case vowel_syllable: /* We made the vowels look like consonants.  So let's call the consonant logic! */
      case consonant_syllable:
       initial_reordering_consonant_syllable (plan, face, buffer, start, end);
       break;
  
      case broken_cluster: /* We already inserted dotted-circles, so just call the standalone_cluster. */
      case standalone_cluster:
       initial_reordering_standalone_cluster (plan, face, buffer, start, end);
       break;
  
      case symbol_cluster:
      case non_indic_cluster:
        break;
    }
  }
  
  static inline void
  insert_dotted_circles (const hb_ot_shape_plan_t *plan HB_UNUSED,
  		       hb_font_t *font,
  		       hb_buffer_t *buffer)
  {
    /* Note: This loop is extra overhead, but should not be measurable. */
    bool has_broken_syllables = false;
    unsigned int count = buffer->len;
    hb_glyph_info_t *info = buffer->info;
    for (unsigned int i = 0; i < count; i++)
      if ((info[i].syllable() & 0x0F) == broken_cluster)
      {
        has_broken_syllables = true;
        break;
      }
    if (likely (!has_broken_syllables))
      return;
  
  
    hb_codepoint_t dottedcircle_glyph;
    if (!font->get_nominal_glyph (0x25CCu, &dottedcircle_glyph))
      return;
  
    hb_glyph_info_t dottedcircle = {0};
    dottedcircle.codepoint = 0x25CCu;
    set_indic_properties (dottedcircle);
    dottedcircle.codepoint = dottedcircle_glyph;
  
    buffer->clear_output ();
  
    buffer->idx = 0;
    unsigned int last_syllable = 0;
    while (buffer->idx < buffer->len && buffer->successful)
    {
      unsigned int syllable = buffer->cur().syllable();
      syllable_type_t syllable_type = (syllable_type_t) (syllable & 0x0F);
      if (unlikely (last_syllable != syllable && syllable_type == broken_cluster))
      {
        last_syllable = syllable;
  
        hb_glyph_info_t ginfo = dottedcircle;
        ginfo.cluster = buffer->cur().cluster;
        ginfo.mask = buffer->cur().mask;
        ginfo.syllable() = buffer->cur().syllable();
        /* TODO Set glyph_props? */
  
        /* Insert dottedcircle after possible Repha. */
        while (buffer->idx < buffer->len && buffer->successful &&
  	     last_syllable == buffer->cur().syllable() &&
  	     buffer->cur().indic_category() == OT_Repha)
          buffer->next_glyph ();
  
        buffer->output_info (ginfo);
      }
      else
        buffer->next_glyph ();
    }
  
    buffer->swap_buffers ();
  }
  
  static void
  initial_reordering (const hb_ot_shape_plan_t *plan,
  		    hb_font_t *font,
  		    hb_buffer_t *buffer)
  {
    update_consonant_positions (plan, font, buffer);
    insert_dotted_circles (plan, font, buffer);
  
    foreach_syllable (buffer, start, end)
      initial_reordering_syllable (plan, font->face, buffer, start, end);
  }
  
  static void
  final_reordering_syllable (const hb_ot_shape_plan_t *plan,
  			   hb_buffer_t *buffer,
  			   unsigned int start, unsigned int end)
  {
    const indic_shape_plan_t *indic_plan = (const indic_shape_plan_t *) plan->data;
    hb_glyph_info_t *info = buffer->info;
  
  
    /* This function relies heavily on halant glyphs.  Lots of ligation
     * and possibly multiple substitutions happened prior to this
     * phase, and that might have messed up our properties.  Recover
     * from a particular case of that where we're fairly sure that a
     * class of OT_H is desired but has been lost. */
    /* We don't call load_virama_glyph(), since we know it's already
     * loaded. */
    hb_codepoint_t virama_glyph = indic_plan->virama_glyph.get_relaxed ();
    if (virama_glyph)
    {
      for (unsigned int i = start; i < end; i++)
        if (info[i].codepoint == virama_glyph &&
  	  _hb_glyph_info_ligated (&info[i]) &&
  	  _hb_glyph_info_multiplied (&info[i]))
        {
          /* This will make sure that this glyph passes is_halant() test. */
  	info[i].indic_category() = OT_H;
  	_hb_glyph_info_clear_ligated_and_multiplied (&info[i]);
        }
    }
  
  
    /* 4. Final reordering:
     *
     * After the localized forms and basic shaping forms GSUB features have been
     * applied (see below), the shaping engine performs some final glyph
     * reordering before applying all the remaining font features to the entire
     * syllable.
     */
  
    bool try_pref = !!indic_plan->mask_array[PREF];
  
    /* Find base again */
    unsigned int base;
    for (base = start; base < end; base++)
      if (info[base].indic_position() >= POS_BASE_C)
      {
        if (try_pref && base + 1 < end)
        {
  	for (unsigned int i = base + 1; i < end; i++)
  	  if ((info[i].mask & indic_plan->mask_array[PREF]) != 0)
  	  {
  	    if (!(_hb_glyph_info_substituted (&info[i]) &&
  		  _hb_glyph_info_ligated_and_didnt_multiply (&info[i])))
  	    {
  	      /* Ok, this was a 'pref' candidate but didn't form any.
  	       * Base is around here... */
  	      base = i;
  	      while (base < end && is_halant (info[base]))
  		base++;
  	      info[base].indic_position() = POS_BASE_C;
  
  	      try_pref = false;
  	    }
  	    break;
  	  }
        }
        /* For Malayalam, skip over unformed below- (but NOT post-) forms. */
        if (buffer->props.script == HB_SCRIPT_MALAYALAM)
        {
  	for (unsigned int i = base + 1; i < end; i++)
  	{
  	  while (i < end && is_joiner (info[i]))
  	    i++;
  	  if (i == end || !is_halant (info[i]))
  	    break;
  	  i++; /* Skip halant. */
  	  while (i < end && is_joiner (info[i]))
  	    i++;
  	  if (i < end && is_consonant (info[i]) && info[i].indic_position() == POS_BELOW_C)
  	  {
  	    base = i;
  	    info[base].indic_position() = POS_BASE_C;
  	  }
  	}
        }
  
        if (start < base && info[base].indic_position() > POS_BASE_C)
          base--;
        break;
      }
    if (base == end && start < base &&
        is_one_of (info[base - 1], FLAG (OT_ZWJ)))
      base--;
    if (base < end)
      while (start < base &&
  	   is_one_of (info[base], (FLAG (OT_N) | FLAG (OT_H))))
        base--;
  
  
    /*   o Reorder matras:
     *
     *     If a pre-base matra character had been reordered before applying basic
     *     features, the glyph can be moved closer to the main consonant based on
     *     whether half-forms had been formed. Actual position for the matra is
     *     defined as “after last standalone halant glyph, after initial matra
     *     position and before the main consonant”. If ZWJ or ZWNJ follow this
     *     halant, position is moved after it.
     *
     * IMPLEMENTATION NOTES:
     *
     * It looks like the last sentence is wrong.  Testing, with Windows 7 Uniscribe
     * and Devanagari shows that the behavior is best described as:
     *
     * "If ZWJ follows this halant, matra is NOT repositioned after this halant.
     *  If ZWNJ follows this halant, position is moved after it."
     *
     * Test case, with Adobe Devanagari or Nirmala UI:
     *
     *   U+091F,U+094D,U+200C,U+092F,U+093F
     *   (Matra moves to the middle, after ZWNJ.)
     *
     *   U+091F,U+094D,U+200D,U+092F,U+093F
     *   (Matra does NOT move, stays to the left.)
     *
     * https://github.com/harfbuzz/harfbuzz/issues/1070
     */
  
    if (start + 1 < end && start < base) /* Otherwise there can't be any pre-base matra characters. */
    {
      /* If we lost track of base, alas, position before last thingy. */
      unsigned int new_pos = base == end ? base - 2 : base - 1;
  
      /* Malayalam / Tamil do not have "half" forms or explicit virama forms.
       * The glyphs formed by 'half' are Chillus or ligated explicit viramas.
       * We want to position matra after them.
       */
      if (buffer->props.script != HB_SCRIPT_MALAYALAM && buffer->props.script != HB_SCRIPT_TAMIL)
      {
      search:
        while (new_pos > start &&
  	     !(is_one_of (info[new_pos], (FLAG (OT_M) | FLAG (OT_H)))))
  	new_pos--;
  
        /* If we found no Halant we are done.
         * Otherwise only proceed if the Halant does
         * not belong to the Matra itself! */
        if (is_halant (info[new_pos]) &&
  	  info[new_pos].indic_position() != POS_PRE_M)
        {
  #if 0 // See comment above
  	/* -> If ZWJ or ZWNJ follow this halant, position is moved after it. */
  	if (new_pos + 1 < end && is_joiner (info[new_pos + 1]))
  	  new_pos++;
  #endif
  	if (new_pos + 1 < end)
  	{
  	  /* -> If ZWJ follows this halant, matra is NOT repositioned after this halant. */
  	  if (info[new_pos + 1].indic_category() == OT_ZWJ)
  	  {
  	    /* Keep searching. */
  	    if (new_pos > start)
  	    {
  	      new_pos--;
  	      goto search;
  	    }
  	  }
  	  /* -> If ZWNJ follows this halant, position is moved after it. */
  	  if (info[new_pos + 1].indic_category() == OT_ZWNJ)
  	    new_pos++;
  	}
        }
        else
          new_pos = start; /* No move. */
      }
  
      if (start < new_pos && info[new_pos].indic_position () != POS_PRE_M)
      {
        /* Now go see if there's actually any matras... */
        for (unsigned int i = new_pos; i > start; i--)
  	if (info[i - 1].indic_position () == POS_PRE_M)
  	{
  	  unsigned int old_pos = i - 1;
  	  if (old_pos < base && base <= new_pos) /* Shouldn't actually happen. */
  	    base--;
  
  	  hb_glyph_info_t tmp = info[old_pos];
  	  memmove (&info[old_pos], &info[old_pos + 1], (new_pos - old_pos) * sizeof (info[0]));
  	  info[new_pos] = tmp;
  
  	  /* Note: this merge_clusters() is intentionally *after* the reordering.
  	   * Indic matra reordering is special and tricky... */
  	  buffer->merge_clusters (new_pos, MIN (end, base + 1));
  
  	  new_pos--;
  	}
      } else {
        for (unsigned int i = start; i < base; i++)
  	if (info[i].indic_position () == POS_PRE_M) {
  	  buffer->merge_clusters (i, MIN (end, base + 1));
  	  break;
  	}
      }
    }
  
  
    /*   o Reorder reph:
     *
     *     Reph’s original position is always at the beginning of the syllable,
     *     (i.e. it is not reordered at the character reordering stage). However,
     *     it will be reordered according to the basic-forms shaping results.
     *     Possible positions for reph, depending on the script, are; after main,
     *     before post-base consonant forms, and after post-base consonant forms.
     */
  
    /* Two cases:
     *
     * - If repha is encoded as a sequence of characters (Ra,H or Ra,H,ZWJ), then
     *   we should only move it if the sequence ligated to the repha form.
     *
     * - If repha is encoded separately and in the logical position, we should only
     *   move it if it did NOT ligate.  If it ligated, it's probably the font trying
     *   to make it work without the reordering.
     */
    if (start + 1 < end &&
        info[start].indic_position() == POS_RA_TO_BECOME_REPH &&
        ((info[start].indic_category() == OT_Repha) ^
         _hb_glyph_info_ligated_and_didnt_multiply (&info[start])))
    {
      unsigned int new_reph_pos;
      reph_position_t reph_pos = indic_plan->config->reph_pos;
  
      /*       1. If reph should be positioned after post-base consonant forms,
       *          proceed to step 5.
       */
      if (reph_pos == REPH_POS_AFTER_POST)
      {
        goto reph_step_5;
      }
  
      /*       2. If the reph repositioning class is not after post-base: target
       *          position is after the first explicit halant glyph between the
       *          first post-reph consonant and last main consonant. If ZWJ or ZWNJ
       *          are following this halant, position is moved after it. If such
       *          position is found, this is the target position. Otherwise,
       *          proceed to the next step.
       *
       *          Note: in old-implementation fonts, where classifications were
       *          fixed in shaping engine, there was no case where reph position
       *          will be found on this step.
       */
      {
        new_reph_pos = start + 1;
        while (new_reph_pos < base && !is_halant (info[new_reph_pos]))
  	new_reph_pos++;
  
        if (new_reph_pos < base && is_halant (info[new_reph_pos]))
        {
  	/* ->If ZWJ or ZWNJ are following this halant, position is moved after it. */
  	if (new_reph_pos + 1 < base && is_joiner (info[new_reph_pos + 1]))
  	  new_reph_pos++;
  	goto reph_move;
        }
      }
  
      /*       3. If reph should be repositioned after the main consonant: find the
       *          first consonant not ligated with main, or find the first
       *          consonant that is not a potential pre-base-reordering Ra.
       */
      if (reph_pos == REPH_POS_AFTER_MAIN)
      {
        new_reph_pos = base;
        while (new_reph_pos + 1 < end && info[new_reph_pos + 1].indic_position() <= POS_AFTER_MAIN)
  	new_reph_pos++;
        if (new_reph_pos < end)
          goto reph_move;
      }
  
      /*       4. If reph should be positioned before post-base consonant, find
       *          first post-base classified consonant not ligated with main. If no
       *          consonant is found, the target position should be before the
       *          first matra, syllable modifier sign or vedic sign.
       */
      /* This is our take on what step 4 is trying to say (and failing, BADLY). */
      if (reph_pos == REPH_POS_AFTER_SUB)
      {
        new_reph_pos = base;
        while (new_reph_pos + 1 < end &&
  	     !( FLAG_UNSAFE (info[new_reph_pos + 1].indic_position()) & (FLAG (POS_POST_C) | FLAG (POS_AFTER_POST) | FLAG (POS_SMVD))))
  	new_reph_pos++;
        if (new_reph_pos < end)
          goto reph_move;
      }
  
      /*       5. If no consonant is found in steps 3 or 4, move reph to a position
       *          immediately before the first post-base matra, syllable modifier
       *          sign or vedic sign that has a reordering class after the intended
       *          reph position. For example, if the reordering position for reph
       *          is post-main, it will skip above-base matras that also have a
       *          post-main position.
       */
      reph_step_5:
      {
        /* Copied from step 2. */
        new_reph_pos = start + 1;
        while (new_reph_pos < base && !is_halant (info[new_reph_pos]))
  	new_reph_pos++;
  
        if (new_reph_pos < base && is_halant (info[new_reph_pos]))
        {
  	/* ->If ZWJ or ZWNJ are following this halant, position is moved after it. */
  	if (new_reph_pos + 1 < base && is_joiner (info[new_reph_pos + 1]))
  	  new_reph_pos++;
  	goto reph_move;
        }
      }
  
      /*       6. Otherwise, reorder reph to the end of the syllable.
       */
      {
        new_reph_pos = end - 1;
        while (new_reph_pos > start && info[new_reph_pos].indic_position() == POS_SMVD)
  	new_reph_pos--;
  
        /*
         * If the Reph is to be ending up after a Matra,Halant sequence,
         * position it before that Halant so it can interact with the Matra.
         * However, if it's a plain Consonant,Halant we shouldn't do that.
         * Uniscribe doesn't do this.
         * TEST: U+0930,U+094D,U+0915,U+094B,U+094D
         */
        if (!hb_options ().uniscribe_bug_compatible &&
  	  unlikely (is_halant (info[new_reph_pos]))) {
  	for (unsigned int i = base + 1; i < new_reph_pos; i++)
  	  if (info[i].indic_category() == OT_M) {
  	    /* Ok, got it. */
  	    new_reph_pos--;
  	  }
        }
        goto reph_move;
      }
  
      reph_move:
      {
        /* Move */
        buffer->merge_clusters (start, new_reph_pos + 1);
        hb_glyph_info_t reph = info[start];
        memmove (&info[start], &info[start + 1], (new_reph_pos - start) * sizeof (info[0]));
        info[new_reph_pos] = reph;
  
        if (start < base && base <= new_reph_pos)
  	base--;
      }
    }
  
  
    /*   o Reorder pre-base-reordering consonants:
     *
     *     If a pre-base-reordering consonant is found, reorder it according to
     *     the following rules:
     */
  
    if (try_pref && base + 1 < end) /* Otherwise there can't be any pre-base-reordering Ra. */
    {
      for (unsigned int i = base + 1; i < end; i++)
        if ((info[i].mask & indic_plan->mask_array[PREF]) != 0)
        {
  	/*       1. Only reorder a glyph produced by substitution during application
  	 *          of the <pref> feature. (Note that a font may shape a Ra consonant with
  	 *          the feature generally but block it in certain contexts.)
  	 */
          /* Note: We just check that something got substituted.  We don't check that
  	 * the <pref> feature actually did it...
  	 *
  	 * Reorder pref only if it ligated. */
  	if (_hb_glyph_info_ligated_and_didnt_multiply (&info[i]))
  	{
  	  /*
  	   *       2. Try to find a target position the same way as for pre-base matra.
  	   *          If it is found, reorder pre-base consonant glyph.
  	   *
  	   *       3. If position is not found, reorder immediately before main
  	   *          consonant.
  	   */
  
  	  unsigned int new_pos = base;
  	  /* Malayalam / Tamil do not have "half" forms or explicit virama forms.
  	   * The glyphs formed by 'half' are Chillus or ligated explicit viramas.
  	   * We want to position matra after them.
  	   */
  	  if (buffer->props.script != HB_SCRIPT_MALAYALAM && buffer->props.script != HB_SCRIPT_TAMIL)
  	  {
  	    while (new_pos > start &&
  		   !(is_one_of (info[new_pos - 1], FLAG(OT_M) | FLAG (OT_H))))
  	      new_pos--;
  	  }
  
  	  if (new_pos > start && is_halant (info[new_pos - 1]))
  	  {
  	    /* -> If ZWJ or ZWNJ follow this halant, position is moved after it. */
  	    if (new_pos < end && is_joiner (info[new_pos]))
  	      new_pos++;
  	  }
  
  	  {
  	    unsigned int old_pos = i;
  
  	    buffer->merge_clusters (new_pos, old_pos + 1);
  	    hb_glyph_info_t tmp = info[old_pos];
  	    memmove (&info[new_pos + 1], &info[new_pos], (old_pos - new_pos) * sizeof (info[0]));
  	    info[new_pos] = tmp;
  
  	    if (new_pos <= base && base < old_pos)
  	      base++;
  	  }
  	}
  
          break;
        }
    }
  
  
    /* Apply 'init' to the Left Matra if it's a word start. */
    if (info[start].indic_position () == POS_PRE_M)
    {
      if (!start ||
  	!(FLAG_UNSAFE (_hb_glyph_info_get_general_category (&info[start - 1])) &
  	 FLAG_RANGE (HB_UNICODE_GENERAL_CATEGORY_FORMAT, HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)))
        info[start].mask |= indic_plan->mask_array[INIT];
      else
        buffer->unsafe_to_break (start - 1, start + 1);
    }
  
  
    /*
     * Finish off the clusters and go home!
     */
    if (hb_options ().uniscribe_bug_compatible)
    {
      switch ((hb_tag_t) plan->props.script)
      {
        case HB_SCRIPT_TAMIL:
        case HB_SCRIPT_SINHALA:
          break;
  
        default:
  	/* Uniscribe merges the entire syllable into a single cluster... Except for Tamil & Sinhala.
  	 * This means, half forms are submerged into the main consonant's cluster.
  	 * This is unnecessary, and makes cursor positioning harder, but that's what
  	 * Uniscribe does. */
  	buffer->merge_clusters (start, end);
  	break;
      }
    }
  }
  
  
  static void
  final_reordering (const hb_ot_shape_plan_t *plan,
  		  hb_font_t *font HB_UNUSED,
  		  hb_buffer_t *buffer)
  {
    unsigned int count = buffer->len;
    if (unlikely (!count)) return;
  
    foreach_syllable (buffer, start, end)
      final_reordering_syllable (plan, buffer, start, end);
  
    HB_BUFFER_DEALLOCATE_VAR (buffer, indic_category);
    HB_BUFFER_DEALLOCATE_VAR (buffer, indic_position);
  }
  
  
  static void
  clear_syllables (const hb_ot_shape_plan_t *plan HB_UNUSED,
  		 hb_font_t *font HB_UNUSED,
  		 hb_buffer_t *buffer)
  {
    hb_glyph_info_t *info = buffer->info;
    unsigned int count = buffer->len;
    for (unsigned int i = 0; i < count; i++)
      info[i].syllable() = 0;
  }
  
  
  static bool
  decompose_indic (const hb_ot_shape_normalize_context_t *c,
  		 hb_codepoint_t  ab,
  		 hb_codepoint_t *a,
  		 hb_codepoint_t *b)
  {
    switch (ab)
    {
      /* Don't decompose these. */
      case 0x0931u  : return false; /* DEVANAGARI LETTER RRA */
      // https://github.com/harfbuzz/harfbuzz/issues/779
      case 0x09DCu  : return false; /* BENGALI LETTER RRA */
      case 0x09DDu  : return false; /* BENGALI LETTER RHA */
      case 0x0B94u  : return false; /* TAMIL LETTER AU */
  
  
      /*
       * Decompose split matras that don't have Unicode decompositions.
       */
  
  #if 0
      /* Gujarati */
      /* This one has no decomposition in Unicode, but needs no decomposition either. */
      /* case 0x0AC9u  : return false; */
  
      /* Oriya */
      case 0x0B57u  : *a = no decomp, -> RIGHT; return true;
  #endif
    }
  
    if ((ab == 0x0DDAu || hb_in_range<hb_codepoint_t> (ab, 0x0DDCu, 0x0DDEu)))
    {
      /*
       * Sinhala split matras...  Let the fun begin.
       *
       * These four characters have Unicode decompositions.  However, Uniscribe
       * decomposes them "Khmer-style", that is, it uses the character itself to
       * get the second half.  The first half of all four decompositions is always
       * U+0DD9.
       *
       * Now, there are buggy fonts, namely, the widely used lklug.ttf, that are
       * broken with Uniscribe.  But we need to support them.  As such, we only
       * do the Uniscribe-style decomposition if the character is transformed into
       * its "sec.half" form by the 'pstf' feature.  Otherwise, we fall back to
       * Unicode decomposition.
       *
       * Note that we can't unconditionally use Unicode decomposition.  That would
       * break some other fonts, that are designed to work with Uniscribe, and
       * don't have positioning features for the Unicode-style decomposition.
       *
       * Argh...
       *
       * The Uniscribe behavior is now documented in the newly published Sinhala
       * spec in 2012:
       *
       *   https://docs.microsoft.com/en-us/typography/script-development/sinhala#shaping
       */
  
      const indic_shape_plan_t *indic_plan = (const indic_shape_plan_t *) c->plan->data;
  
      hb_codepoint_t glyph;
  
      if (hb_options ().uniscribe_bug_compatible ||
  	(c->font->get_nominal_glyph (ab, &glyph) &&
  	 indic_plan->pstf.would_substitute (&glyph, 1, c->font->face)))
      {
        /* Ok, safe to use Uniscribe-style decomposition. */
        *a = 0x0DD9u;
        *b = ab;
        return true;
      }
    }
  
    return (bool) c->unicode->decompose (ab, a, b);
  }
  
  static bool
  compose_indic (const hb_ot_shape_normalize_context_t *c,
  	       hb_codepoint_t  a,
  	       hb_codepoint_t  b,
  	       hb_codepoint_t *ab)
  {
    /* Avoid recomposing split matras. */
    if (HB_UNICODE_GENERAL_CATEGORY_IS_MARK (c->unicode->general_category (a)))
      return false;
  
    /* Composition-exclusion exceptions that we want to recompose. */
    if (a == 0x09AFu && b == 0x09BCu) { *ab = 0x09DFu; return true; }
  
    return (bool) c->unicode->compose (a, b, ab);
  }
  
  
  const hb_ot_complex_shaper_t _hb_ot_complex_shaper_indic =
  {
    collect_features_indic,
    override_features_indic,
    data_create_indic,
    data_destroy_indic,
    nullptr, /* preprocess_text */
    nullptr, /* postprocess_glyphs */
    HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT,
    decompose_indic,
    compose_indic,
    setup_masks_indic,
    nullptr, /* disable_otl */
    nullptr, /* reorder_marks */
    HB_OT_SHAPE_ZERO_WIDTH_MARKS_NONE,
    false, /* fallback_position */
  };
  