tor-browser

hb-ot-shaper-indic.cc (51073B)

---

/*
* 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.hh"

#ifndef HB_NO_OT_SHAPE

#include "hb-ot-shaper-indic.hh"
#include "hb-ot-shaper-indic-machine.hh"
#include "hb-ot-shaper-vowel-constraints.hh"
#include "hb-ot-layout.hh"


/*
* Indic shaper.
*/


static inline void
set_indic_properties (hb_glyph_info_t &info)
{
 hb_codepoint_t u = info.codepoint;
 unsigned int type = hb_indic_get_categories (u);

 info.indic_category() = (indic_category_t) (type & 0xFFu);
 info.indic_position() = (indic_position_t) (type >> 8);
}


static inline bool
is_one_of (const hb_glyph_info_t &info, unsigned int flags)
{
 /* If it ligated, all bets are off. */
 if (_hb_glyph_info_ligated (&info)) return false;
 return !!(FLAG_UNSAFE (info.indic_category()) & flags);
}

/* Note:
*
* We treat Vowels and placeholders as if they were consonants.  This is safe because Vowels
* cannot happen in a consonant syllable.  The plus side however is, we can call the
* consonant syllable logic from the vowel syllable function and get it all right!
*
* Keep in sync with consonant_categories in the generator. */
#define CONSONANT_FLAGS_INDIC (FLAG (I_Cat(C)) | FLAG (I_Cat(CS)) | FLAG (I_Cat(Ra)) | FLAG (I_Cat(CM)) | FLAG (I_Cat(V)) | FLAG (I_Cat(PLACEHOLDER)) | FLAG (I_Cat(DOTTEDCIRCLE)))

static inline bool
is_consonant (const hb_glyph_info_t &info)
{
 return is_one_of (info, CONSONANT_FLAGS_INDIC);
}

#define JOINER_FLAGS (FLAG (I_Cat(ZWJ)) | FLAG (I_Cat(ZWNJ)))

static inline bool
is_joiner (const hb_glyph_info_t &info)
{
 return is_one_of (info, JOINER_FLAGS);
}

static inline bool
is_halant (const hb_glyph_info_t &info)
{
 return is_one_of (info, FLAG (I_Cat(H)));
}

struct hb_indic_would_substitute_feature_t
{
 void init (const hb_ot_map_t *map, hb_tag_t feature_tag, bool zero_context_)
 {
   zero_context = zero_context_;
   lookups = map->get_stage_lookups (0/*GSUB*/,
			      map->get_feature_stage (0/*GSUB*/, feature_tag));
 }

 bool would_substitute (const hb_codepoint_t *glyphs,
		 unsigned int          glyphs_count,
		 hb_face_t            *face) const
 {
   for (const auto &lookup : lookups)
     if (hb_ot_layout_lookup_would_substitute (face, lookup.index, glyphs, glyphs_count, zero_context))
return true;
   return false;
 }

 private:
 hb_array_t<const hb_ot_map_t::lookup_map_t> lookups;
 bool zero_context;
};


/*
* 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 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;
 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,REPH_POS_BEFORE_POST,REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
 {HB_SCRIPT_DEVANAGARI,true, 0x094Du,REPH_POS_BEFORE_POST,REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
 {HB_SCRIPT_BENGALI,	true, 0x09CDu,REPH_POS_AFTER_SUB,  REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
 {HB_SCRIPT_GURMUKHI,	true, 0x0A4Du,REPH_POS_BEFORE_SUB, REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
 {HB_SCRIPT_GUJARATI,	true, 0x0ACDu,REPH_POS_BEFORE_POST,REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
 {HB_SCRIPT_ORIYA,	true, 0x0B4Du,REPH_POS_AFTER_MAIN, REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
 {HB_SCRIPT_TAMIL,	true, 0x0BCDu,REPH_POS_AFTER_POST, REPH_MODE_IMPLICIT, BLWF_MODE_PRE_AND_POST},
 {HB_SCRIPT_TELUGU,	true, 0x0C4Du,REPH_POS_AFTER_POST, REPH_MODE_EXPLICIT, BLWF_MODE_POST_ONLY},
 {HB_SCRIPT_KANNADA,	true, 0x0CCDu,REPH_POS_AFTER_POST, REPH_MODE_IMPLICIT, BLWF_MODE_POST_ONLY},
 {HB_SCRIPT_MALAYALAM,	true, 0x0D4Du,REPH_POS_AFTER_MAIN, REPH_MODE_LOG_REPHA,BLWF_MODE_PRE_AND_POST},
};


static const hb_ot_map_feature_t
indic_features[] =
{
 /*
  * Basic features.
  * These features are applied in order, one at a time, after initial_reordering,
  * constrained to the syllable.
  */
 {HB_TAG('n','u','k','t'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('a','k','h','n'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('r','p','h','f'),        F_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('r','k','r','f'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('p','r','e','f'),        F_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('b','l','w','f'),        F_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('a','b','v','f'),        F_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('h','a','l','f'),        F_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('p','s','t','f'),        F_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('v','a','t','u'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('c','j','c','t'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
 /*
  * Other features.
  * These features are applied all at once, after final_reordering, constrained
  * to the syllable.
  * Default Bengali font in Windows for example has intermixed
  * lookups for init,pres,abvs,blws features.
  */
 {HB_TAG('i','n','i','t'),        F_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('p','r','e','s'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('a','b','v','s'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('b','l','w','s'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('p','s','t','s'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
 {HB_TAG('h','a','l','n'), F_GLOBAL_MANUAL_JOINERS | F_PER_SYLLABLE},
};

/*
* Must be in the same order as the indic_features array.
*/
enum {
 _INDIC_NUKT,
 _INDIC_AKHN,
 INDIC_RPHF,
 _INDIC_RKRF,
 INDIC_PREF,
 INDIC_BLWF,
 INDIC_ABVF,
 INDIC_HALF,
 INDIC_PSTF,
 _INDIC_VATU,
 _INDIC_CJCT,

 INDIC_INIT,
 _INDIC_PRES,
 _INDIC_ABVS,
 _INDIC_BLWS,
 _INDIC_PSTS,
 _INDIC_HALN,

 INDIC_NUM_FEATURES,
 INDIC_BASIC_FEATURES = INDIC_INIT, /* Don't forget to update this! */
};

static bool
setup_syllables_indic (const hb_ot_shape_plan_t *plan,
	       hb_font_t *font,
	       hb_buffer_t *buffer);
static bool
initial_reordering_indic (const hb_ot_shape_plan_t *plan,
		  hb_font_t *font,
		  hb_buffer_t *buffer);
static bool
final_reordering_indic (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_indic);

 map->enable_feature (HB_TAG('l','o','c','l'), F_PER_SYLLABLE);
 /* 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->enable_feature (HB_TAG('c','c','m','p'), F_PER_SYLLABLE);


 unsigned int i = 0;
 map->add_gsub_pause (initial_reordering_indic);

 for (; i < INDIC_BASIC_FEATURES; i++) {
   map->add_feature (indic_features[i]);
   map->add_gsub_pause (nullptr);
 }

 map->add_gsub_pause (final_reordering_indic);

 for (; i < INDIC_NUM_FEATURES; i++)
   map->add_feature (indic_features[i]);
}

static void
override_features_indic (hb_ot_shape_planner_t *plan)
{
 plan->map.disable_feature (HB_TAG('l','i','g','a'));
 plan->map.add_gsub_pause (hb_syllabic_clear_var); // Don't need syllables anymore, use stop to free buffer var
}


struct indic_shape_plan_t
{
 bool load_virama_glyph (hb_font_t *font, hb_codepoint_t *pglyph) const
 {
   hb_codepoint_t glyph = virama_glyph;
   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 = (int) glyph;
   }

   *pglyph = glyph;
   return glyph != 0;
 }

 const indic_config_t *config;

 bool is_old_spec;
 mutable hb_atomic_t<hb_codepoint_t> virama_glyph;

 hb_indic_would_substitute_feature_t rphf;
 hb_indic_would_substitute_feature_t pref;
 hb_indic_would_substitute_feature_t blwf;
 hb_indic_would_substitute_feature_t pstf;
 hb_indic_would_substitute_feature_t vatu;

 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 *) hb_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 = -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);
 indic_plan->vatu.init (&plan->map, HB_TAG('v','a','t','u'), 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)
{
 hb_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.
  *
  * Vatu is done as well, for:
  * https://github.com/harfbuzz/harfbuzz/issues/1587
  */
 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) ||
     indic_plan->vatu.would_substitute (glyphs  , 2, face) ||
     indic_plan->vatu.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;
}

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 bool
setup_syllables_indic (const hb_ot_shape_plan_t *plan HB_UNUSED,
	       hb_font_t *font HB_UNUSED,
	       hb_buffer_t *buffer)
{
 HB_BUFFER_ALLOCATE_VAR (buffer, syllable);
 find_syllables_indic (buffer);
 foreach_syllable (buffer, start, end)
   buffer->unsafe_to_break (start, end);
 return false;
}

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 (int) a - (int) b;
}



static void
update_consonant_positions_indic (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;

 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 (I_Cat(Ra))) &&
     is_one_of (info[start+1], FLAG (I_Cat(H))) &&
     is_one_of (info[start+2], FLAG (I_Cat(ZWJ))))
 {
   buffer->merge_clusters (start+1, start+3);
   hb_swap (info[start+1], info[start+2]);
 }

 /* 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[INDIC_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() == I_Cat(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() == I_Cat(Repha))
   {
limit += 1;
while (limit < end && is_joiner (info[limit]))
  limit++;
base = start;
has_reph = true;
   }

   {
     /* -> 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() == I_Cat(ZWJ) &&
      info[i - 1].indic_category() == I_Cat(H))
    break;
}
     } while (i > limit);
   }

   /* -> 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() = hb_min (POS_PRE_C, (indic_position_t) info[i].indic_position());

 if (base < end)
   info[base].indic_position() = POS_BASE_C;

 /* 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 block 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() == I_Cat(H))
     {
unsigned int j;
for (j = end - 1; j > i; j--)
  if (is_consonant (info[j]) ||
      (disallow_double_halants && info[j].indic_category() == I_Cat(H)))
    break;
if (info[j].indic_category() != I_Cat(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 (I_Cat(N)) | FLAG (I_Cat(RS)) | FLAG (I_Cat(CM)) | FLAG (I_Cat(H)))))
     {
info[i].indic_position() = last_pos;
if (unlikely (info[i].indic_category() == I_Cat(H) &&
	      info[i].indic_position() == POS_PRE_M))
{
  /*
   * Uniscribe doesn't move the Halant with Left Matra.
   * TEST: U+092B,U+093F,U+094D
   * We follow.
   */
  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) {
if (info[i].indic_category() == I_Cat(MPst) &&
    i > start && info[i - 1].indic_category() == I_Cat(SM))
  info[i - 1].indic_position() = info[i].indic_position();
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 (FLAG_UNSAFE (info[i].indic_category()) & (FLAG (I_Cat(M)) | FLAG (I_Cat(MPst))))
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; also flip left-matra sequence. */
   unsigned first_left_matra = end;
   unsigned last_left_matra = end;
   base = end;
   for (unsigned int i = start; i < end; i++)
   {
     if (info[i].indic_position() == POS_BASE_C)
     {
base = i;
break;
     }
     else if (info[i].indic_position() == POS_PRE_M)
     {
       if (first_left_matra == end)
  first_left_matra = i;
last_left_matra = i;
     }
   }
   /* https://github.com/harfbuzz/harfbuzz/issues/3863 */
   if (first_left_matra < last_left_matra)
   {
     /* No need to merge clusters, handled later. */
     buffer->reverse_range (first_left_matra, last_left_matra + 1);
     /* Reverse back nuktas, etc. */
     unsigned i = first_left_matra;
     for (unsigned j = i; j <= last_left_matra; j++)
if (FLAG_UNSAFE (info[j].indic_category()) & (FLAG (I_Cat(M)) | FLAG (I_Cat(MPst))))
{
  buffer->reverse_range (i, j + 1);
  i = j + 1;
}
   }

   /* 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...
    * We don't want to merge_clusters all of that, which buffer->sort()
    * would.  Here's a concrete example:
    *
    * Assume there's a pre-base consonant and explicit Halant before base,
    * followed by a prebase-reordering (left) Matra:
    *
    *   C,H,ZWNJ,B,M
    *
    * At this point in reordering we would have:
    *
    *   M,C,H,ZWNJ,B
    *
    * whereas in final reordering we will bring the Matra closer to Base:
    *
    *   C,H,ZWNJ,M,B
    *
    * That's why we don't want to merge-clusters anything before the Base
    * at this point.  But if something moved from after Base to before it,
    * we should merge clusters from base to them.  In final-reordering, we
    * only move things around before base, and merge-clusters up to base.
    * These two merge-clusters from the two sides of base will interlock
    * to merge things correctly.  See:
    * https://github.com/harfbuzz/harfbuzz/issues/2272
    */
   if (indic_plan->is_old_spec || end - start > 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 min = i;
  unsigned int max = i;
  unsigned int j = start + info[i].syllable();
  while (j != i)
  {
    min = hb_min (min, j);
    max = hb_max (max, j);
    unsigned int next = start + info[j].syllable();
    info[j].syllable() = 255; /* So we don't process j later again. */
    j = next;
  }
  buffer->merge_clusters (hb_max (base, min), 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[INDIC_RPHF];

   /* Pre-base */
   mask = indic_plan->mask_array[INDIC_HALF];
   if (!indic_plan->is_old_spec &&
indic_plan->config->blwf_mode == BLWF_MODE_PRE_AND_POST)
     mask |= indic_plan->mask_array[INDIC_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[INDIC_BLWF] |
   indic_plan->mask_array[INDIC_ABVF] |
   indic_plan->mask_array[INDIC_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() == I_Cat(Ra) &&
  info[i+1].indic_category() == I_Cat(H)  &&
  (i + 2 == base ||
   info[i+2].indic_category() != I_Cat(ZWJ)))
     {
info[i  ].mask |= indic_plan->mask_array[INDIC_BLWF];
info[i+1].mask |= indic_plan->mask_array[INDIC_BLWF];
     }
 }

 unsigned int pref_len = 2;
 if (indic_plan->mask_array[INDIC_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[INDIC_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() == I_Cat(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[INDIC_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... */

 initial_reordering_consonant_syllable (plan, face, buffer, start, end);
}

static void
initial_reordering_syllable_indic (const hb_ot_shape_plan_t *plan,
			   hb_face_t *face,
			   hb_buffer_t *buffer,
			   unsigned int start, unsigned int end)
{
 indic_syllable_type_t syllable_type = (indic_syllable_type_t) (buffer->info[start].syllable() & 0x0F);
 switch (syllable_type)
 {
   case indic_vowel_syllable: /* We made the vowels look like consonants.  So let's call the consonant logic! */
   case indic_consonant_syllable:
    initial_reordering_consonant_syllable (plan, face, buffer, start, end);
    break;

   case indic_broken_cluster: /* We already inserted dotted-circles, so just call the standalone_cluster. */
   case indic_standalone_cluster:
    initial_reordering_standalone_cluster (plan, face, buffer, start, end);
    break;

   case indic_symbol_cluster:
   case indic_non_indic_cluster:
     break;
 }
}

static bool
initial_reordering_indic (const hb_ot_shape_plan_t *plan,
		  hb_font_t *font,
		  hb_buffer_t *buffer)
{
 bool ret = false;
 if (!buffer->message (font, "start reordering indic initial"))
   return ret;

 update_consonant_positions_indic (plan, font, buffer);
 if (hb_syllabic_insert_dotted_circles (font, buffer,
				 indic_broken_cluster,
				 I_Cat(DOTTEDCIRCLE),
				 I_Cat(Repha),
				 POS_END))
   ret = true;

 foreach_syllable (buffer, start, end)
   initial_reordering_syllable_indic (plan, font->face, buffer, start, end);

 (void) buffer->message (font, "end reordering indic initial");

 return ret;
}

static void
final_reordering_syllable_indic (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 I_Cat(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;
 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() = I_Cat(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[INDIC_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[INDIC_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++;
      if (base < end)
	info[base].indic_position() = POS_BASE_C;

      try_pref = false;
    }
    break;
  }
if (base == end)
  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 (I_Cat(ZWJ))))
   base--;
 if (base < end)
   while (start < base &&
   is_one_of (info[base], (FLAG (I_Cat(N)) | FLAG (I_Cat(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 (I_Cat(M)) | FLAG (I_Cat(MPst)) | FLAG (I_Cat(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() == I_Cat(ZWJ))
  {
    /* Keep searching. */
    if (new_pos > start)
    {
      new_pos--;
      goto search;
    }
  }
  /* -> If ZWNJ follows this halant, position is moved after it.
   *
   * IMPLEMENTATION NOTES:
   *
   * This is taken care of by the state-machine. A Halant,ZWNJ is a terminating
   * sequence for a consonant syllable; any pre-base matras occurring after it
   * will belong to the subsequent syllable.
   */
}
     }
     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, hb_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, hb_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() == I_Cat(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;
     }
   }
   /* See https://github.com/harfbuzz/harfbuzz/issues/2298#issuecomment-615318654 */

   /*       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 (unlikely (is_halant (info[new_reph_pos])))
     {
for (unsigned int i = base + 1; i < new_reph_pos; i++)
  if (FLAG_UNSAFE (info[i].indic_category()) & (FLAG (I_Cat(M)) | FLAG (I_Cat(MPst))))
  {
    /* 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[INDIC_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 (I_Cat(M)) | FLAG (I_Cat(MPst)) | FLAG (I_Cat(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[INDIC_INIT];
   else
     buffer->unsafe_to_break (start - 1, start + 1);
 }
}


static bool
final_reordering_indic (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 false;

 if (buffer->message (font, "start reordering indic final")) {
   foreach_syllable (buffer, start, end)
     final_reordering_syllable_indic (plan, buffer, start, end);
   (void) buffer->message (font, "end reordering indic final");
 }

 HB_BUFFER_DEALLOCATE_VAR (buffer, indic_category);
 HB_BUFFER_DEALLOCATE_VAR (buffer, indic_position);

 return false;
}


static void
preprocess_text_indic (const hb_ot_shape_plan_t *plan,
	       hb_buffer_t              *buffer,
	       hb_font_t                *font)
{
 _hb_preprocess_text_vowel_constraints (plan, buffer, font);
}

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
 }

 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_shaper_t _hb_ot_shaper_indic =
{
 collect_features_indic,
 override_features_indic,
 data_create_indic,
 data_destroy_indic,
 preprocess_text_indic,
 nullptr, /* postprocess_glyphs */
 decompose_indic,
 compose_indic,
 setup_masks_indic,
 nullptr, /* reorder_marks */
 HB_TAG_NONE, /* gpos_tag */
 HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT,
 HB_OT_SHAPE_ZERO_WIDTH_MARKS_NONE,
 false, /* fallback_position */
};


#endif