src/hb-graphite2.cc - third_party/harfbuzz - Git at Google

 /*
  * Copyright © 2011  Martin Hosken
  * Copyright © 2011  SIL International
  * 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"

 #ifdef HAVE_GRAPHITE2

 #include "hb-shaper-impl.hh"

 #include "hb-graphite2.h"

 #include <graphite2/Segment.h>

 #include "hb-ot-layout.h"


 /**
  * SECTION:hb-graphite2
  * @title: hb-graphite2
  * @short_description: Graphite2 integration
  * @include: hb-graphite2.h
  *
  * Functions for using HarfBuzz with fonts that include Graphite features.
  *
  * For Graphite features to work, you must be sure that HarfBuzz was compiled
  * with the `graphite2` shaping engine enabled. Currently, the default is to
  * not enable `graphite2` shaping.
  **/


 /*
  * shaper face data
  */

 typedef struct hb_graphite2_tablelist_t
 {
   struct hb_graphite2_tablelist_t *next;
   hb_blob_t *blob;
   unsigned int tag;
 } hb_graphite2_tablelist_t;

 struct hb_graphite2_face_data_t
 {
   hb_face_t *face;
   gr_face   *grface;
   hb_atomic_ptr_t<hb_graphite2_tablelist_t> tlist;
 };

 static const void *hb_graphite2_get_table (const void *data, unsigned int tag, size_t *len)
 {
   hb_graphite2_face_data_t *face_data = (hb_graphite2_face_data_t *) data;
   hb_graphite2_tablelist_t *tlist = face_data->tlist;

   hb_blob_t *blob = nullptr;

   for (hb_graphite2_tablelist_t *p = tlist; p; p = p->next)
     if (p->tag == tag) {
       blob = p->blob;
       break;
     }

   if (unlikely (!blob))
   {
     blob = face_data->face->reference_table (tag);

     hb_graphite2_tablelist_t *p = (hb_graphite2_tablelist_t *) hb_calloc (1, sizeof (hb_graphite2_tablelist_t));
     if (unlikely (!p)) {
       hb_blob_destroy (blob);
       return nullptr;
     }
     p->blob = blob;
     p->tag = tag;

 retry:
     hb_graphite2_tablelist_t *tlist = face_data->tlist;
     p->next = tlist;

     if (unlikely (!face_data->tlist.cmpexch (tlist, p)))
       goto retry;
   }

   unsigned int tlen;
   const char *d = hb_blob_get_data (blob, &tlen);
   *len = tlen;
   return d;
 }

 hb_graphite2_face_data_t *
 _hb_graphite2_shaper_face_data_create (hb_face_t *face)
 {
   hb_blob_t *silf_blob = face->reference_table (HB_GRAPHITE2_TAG_SILF);
   /* Umm, we just reference the table to check whether it exists.
    * Maybe add better API for this? */
   if (!hb_blob_get_length (silf_blob))
   {
     hb_blob_destroy (silf_blob);
     return nullptr;
   }
   hb_blob_destroy (silf_blob);

   hb_graphite2_face_data_t *data = (hb_graphite2_face_data_t *) hb_calloc (1, sizeof (hb_graphite2_face_data_t));
   if (unlikely (!data))
     return nullptr;

   data->face = face;
   const gr_face_ops ops = {sizeof(gr_face_ops), &hb_graphite2_get_table, NULL};
   data->grface = gr_make_face_with_ops (data, &ops, gr_face_preloadAll);

   if (unlikely (!data->grface)) {
     hb_free (data);
     return nullptr;
   }

   return data;
 }

 void
 _hb_graphite2_shaper_face_data_destroy (hb_graphite2_face_data_t *data)
 {
   hb_graphite2_tablelist_t *tlist = data->tlist;

   while (tlist)
   {
     hb_graphite2_tablelist_t *old = tlist;
     hb_blob_destroy (tlist->blob);
     tlist = tlist->next;
     hb_free (old);
   }

   gr_face_destroy (data->grface);

   hb_free (data);
 }

 /**
  * hb_graphite2_face_get_gr_face: (skip)
  * @face: @hb_face_t to query
  *
  * Fetches the Graphite2 gr_face corresponding to the specified
  * #hb_face_t face object.
  *
  * Return value: the gr_face found
  *
  * Since: 0.9.10
  */
 gr_face *
 hb_graphite2_face_get_gr_face (hb_face_t *face)
 {
   const hb_graphite2_face_data_t *data = face->data.graphite2;
   return data ? data->grface : nullptr;
 }


 /*
  * shaper font data
  */

 struct hb_graphite2_font_data_t {};

 hb_graphite2_font_data_t *
 _hb_graphite2_shaper_font_data_create (hb_font_t *font HB_UNUSED)
 {
   return (hb_graphite2_font_data_t *) HB_SHAPER_DATA_SUCCEEDED;
 }

 void
 _hb_graphite2_shaper_font_data_destroy (hb_graphite2_font_data_t *data HB_UNUSED)
 {
 }

 #ifndef HB_DISABLE_DEPRECATED
 /**
  * hb_graphite2_font_get_gr_font: (skip)
  * @font: An #hb_font_t
  *
  * Always returns `NULL`. Use hb_graphite2_face_get_gr_face() instead.
  *
  * Return value: (nullable): Graphite2 font associated with @font.
  *
  * Since: 0.9.10
  * Deprecated: 1.4.2
  */
 gr_font *
 hb_graphite2_font_get_gr_font (hb_font_t *font HB_UNUSED)
 {
   return nullptr;
 }
 #endif


 /*
  * shaper
  */

 struct hb_graphite2_cluster_t {
   unsigned int base_char;
   unsigned int num_chars;
   unsigned int base_glyph;
   unsigned int num_glyphs;
   unsigned int cluster;
   int advance;
 };

 hb_bool_t
 _hb_graphite2_shape (hb_shape_plan_t    *shape_plan HB_UNUSED,
 		     hb_font_t          *font,
 		     hb_buffer_t        *buffer,
 		     const hb_feature_t *features,
 		     unsigned int        num_features)
 {
   hb_face_t *face = font->face;
   gr_face *grface = face->data.graphite2->grface;

   const char *lang = hb_language_to_string (hb_buffer_get_language (buffer));
   const char *lang_end = lang ? strchr (lang, '-') : nullptr;
   int lang_len = lang_end ? lang_end - lang : -1;
   gr_feature_val *feats = gr_face_featureval_for_lang (grface, lang ? hb_tag_from_string (lang, lang_len) : 0);

   for (unsigned int i = 0; i < num_features; i++)
   {
     const gr_feature_ref *fref = gr_face_find_fref (grface, features[i].tag);
     if (fref)
       gr_fref_set_feature_value (fref, features[i].value, feats);
   }

   hb_direction_t direction = buffer->props.direction;
   hb_direction_t horiz_dir = hb_script_get_horizontal_direction (buffer->props.script);
   /* TODO vertical:
    * The only BTT vertical script is Ogham, but it's not clear to me whether OpenType
    * Ogham fonts are supposed to be implemented BTT or not.  Need to research that
    * first. */
   if ((HB_DIRECTION_IS_HORIZONTAL (direction) &&
        direction != horiz_dir && horiz_dir != HB_DIRECTION_INVALID) ||
       (HB_DIRECTION_IS_VERTICAL   (direction) &&
        direction != HB_DIRECTION_TTB))
   {
     hb_buffer_reverse_clusters (buffer);
     direction = HB_DIRECTION_REVERSE (direction);
   }

   gr_segment *seg = nullptr;
   const gr_slot *is;
   unsigned int ci = 0, ic = 0;
   unsigned int curradvx = 0, curradvy = 0;

   unsigned int scratch_size;
   hb_buffer_t::scratch_buffer_t *scratch = buffer->get_scratch_buffer (&scratch_size);

   uint32_t *chars = (uint32_t *) scratch;

   for (unsigned int i = 0; i < buffer->len; ++i)
     chars[i] = buffer->info[i].codepoint;

   seg = gr_make_seg (nullptr, grface,
 		     HB_TAG_NONE, // https://github.com/harfbuzz/harfbuzz/issues/3439#issuecomment-1442650148
 		     feats,
 		     gr_utf32, chars, buffer->len,
 		     2 | (direction == HB_DIRECTION_RTL ? 1 : 0));

   if (unlikely (!seg)) {
     if (feats) gr_featureval_destroy (feats);
     return false;
   }

   unsigned int glyph_count = gr_seg_n_slots (seg);
   if (unlikely (!glyph_count)) {
     if (feats) gr_featureval_destroy (feats);
     gr_seg_destroy (seg);
     buffer->len = 0;
     return true;
   }

   (void) buffer->ensure (glyph_count);
   scratch = buffer->get_scratch_buffer (&scratch_size);
   while ((DIV_CEIL (sizeof (hb_graphite2_cluster_t) * buffer->len, sizeof (*scratch)) +
 	  DIV_CEIL (sizeof (hb_codepoint_t) * glyph_count, sizeof (*scratch))) > scratch_size)
   {
     if (unlikely (!buffer->ensure (buffer->allocated * 2)))
     {
       if (feats) gr_featureval_destroy (feats);
       gr_seg_destroy (seg);
       return false;
     }
     scratch = buffer->get_scratch_buffer (&scratch_size);
   }

 #define ALLOCATE_ARRAY(Type, name, len) \
   Type *name = (Type *) scratch; \
   do { \
     unsigned int _consumed = DIV_CEIL ((len) * sizeof (Type), sizeof (*scratch)); \
     assert (_consumed <= scratch_size); \
     scratch += _consumed; \
     scratch_size -= _consumed; \
   } while (0)

   ALLOCATE_ARRAY (hb_graphite2_cluster_t, clusters, buffer->len);
   ALLOCATE_ARRAY (hb_codepoint_t, gids, glyph_count);

 #undef ALLOCATE_ARRAY

   hb_memset (clusters, 0, sizeof (clusters[0]) * buffer->len);

   hb_codepoint_t *pg = gids;
   clusters[0].cluster = buffer->info[0].cluster;
   unsigned int upem = hb_face_get_upem (face);
   float xscale = (float) font->x_scale / upem;
   float yscale = (float) font->y_scale / upem;
   yscale *= yscale / xscale;
   unsigned int curradv = 0;
   if (HB_DIRECTION_IS_BACKWARD (direction))
   {
     curradv = gr_slot_origin_X(gr_seg_first_slot(seg)) * xscale;
     clusters[0].advance = gr_seg_advance_X(seg) * xscale - curradv;
   }
   else
     clusters[0].advance = 0;
   for (is = gr_seg_first_slot (seg), ic = 0; is; is = gr_slot_next_in_segment (is), ic++)
   {
     unsigned int before = gr_slot_before (is);
     unsigned int after = gr_slot_after (is);
     *pg = gr_slot_gid (is);
     pg++;
     while (clusters[ci].base_char > before && ci)
     {
       clusters[ci-1].num_chars += clusters[ci].num_chars;
       clusters[ci-1].num_glyphs += clusters[ci].num_glyphs;
       clusters[ci-1].advance += clusters[ci].advance;
       ci--;
     }

     if (gr_slot_can_insert_before (is) && clusters[ci].num_chars && before >= clusters[ci].base_char + clusters[ci].num_chars)
     {
       hb_graphite2_cluster_t *c = clusters + ci + 1;
       c->base_char = clusters[ci].base_char + clusters[ci].num_chars;
       c->cluster = buffer->info[c->base_char].cluster;
       c->num_chars = before - c->base_char;
       c->base_glyph = ic;
       c->num_glyphs = 0;
       if (HB_DIRECTION_IS_BACKWARD (direction))
       {
 	c->advance = curradv - gr_slot_origin_X(is) * xscale;
 	curradv -= c->advance;
       }
       else
       {
 	auto origin_X = gr_slot_origin_X (is) * xscale;
 	c->advance = 0;
 	clusters[ci].advance += origin_X - curradv;
 	curradv = origin_X;
       }
       ci++;
     }
     clusters[ci].num_glyphs++;

     if (clusters[ci].base_char + clusters[ci].num_chars < after + 1)
 	clusters[ci].num_chars = after + 1 - clusters[ci].base_char;
   }

   if (HB_DIRECTION_IS_BACKWARD (direction))
     clusters[ci].advance += curradv;
   else
     clusters[ci].advance += gr_seg_advance_X(seg) * xscale - curradv;
   ci++;

   for (unsigned int i = 0; i < ci; ++i)
   {
     for (unsigned int j = 0; j < clusters[i].num_glyphs; ++j)
     {
       hb_glyph_info_t *info = &buffer->info[clusters[i].base_glyph + j];
       info->codepoint = gids[clusters[i].base_glyph + j];
       info->cluster = clusters[i].cluster;
       info->var1.i32 = clusters[i].advance;     // all glyphs in the cluster get the same advance
     }
   }
   buffer->len = glyph_count;

   /* Positioning. */
   unsigned int currclus = UINT_MAX;
   const hb_glyph_info_t *info = buffer->info;
   hb_glyph_position_t *pPos = hb_buffer_get_glyph_positions (buffer, nullptr);
   if (!HB_DIRECTION_IS_BACKWARD (direction))
   {
     curradvx = 0;
     for (is = gr_seg_first_slot (seg); is; pPos++, ++info, is = gr_slot_next_in_segment (is))
     {
       pPos->x_offset = gr_slot_origin_X (is) * xscale - curradvx;
       pPos->y_offset = gr_slot_origin_Y (is) * yscale - curradvy;
       if (info->cluster != currclus) {
 	pPos->x_advance = info->var1.i32;
 	curradvx += pPos->x_advance;
 	currclus = info->cluster;
       } else
 	pPos->x_advance = 0.;

       pPos->y_advance = gr_slot_advance_Y (is, grface, nullptr) * yscale;
       curradvy += pPos->y_advance;
     }
   }
   else
   {
     curradvx = gr_seg_advance_X(seg) * xscale;
     for (is = gr_seg_first_slot (seg); is; pPos++, info++, is = gr_slot_next_in_segment (is))
     {
       if (info->cluster != currclus)
       {
 	pPos->x_advance = info->var1.i32;
 	curradvx -= pPos->x_advance;
 	currclus = info->cluster;
       } else
 	pPos->x_advance = 0.;

       pPos->y_advance = gr_slot_advance_Y (is, grface, nullptr) * yscale;
       curradvy -= pPos->y_advance;
       pPos->x_offset = gr_slot_origin_X (is) * xscale - info->var1.i32 - curradvx + pPos->x_advance;
       pPos->y_offset = gr_slot_origin_Y (is) * yscale - curradvy;
     }
     hb_buffer_reverse_clusters (buffer);
   }

   if (feats) gr_featureval_destroy (feats);
   gr_seg_destroy (seg);

   buffer->clear_glyph_flags ();
   buffer->unsafe_to_break ();

   return true;
 }


 #endif
	/*
	* Copyright © 2011 Martin Hosken
	* Copyright © 2011 SIL International
	* 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"

	#ifdef HAVE_GRAPHITE2

	#include "hb-shaper-impl.hh"

	#include "hb-graphite2.h"

	#include <graphite2/Segment.h>

	#include "hb-ot-layout.h"


	/**
	* SECTION:hb-graphite2
	* @title: hb-graphite2
	* @short_description: Graphite2 integration
	* @include: hb-graphite2.h
	*
	* Functions for using HarfBuzz with fonts that include Graphite features.
	*
	* For Graphite features to work, you must be sure that HarfBuzz was compiled
	* with the `graphite2` shaping engine enabled. Currently, the default is to
	* not enable `graphite2` shaping.
	**/


	/*
	* shaper face data
	*/

	typedef struct hb_graphite2_tablelist_t
	{
	struct hb_graphite2_tablelist_t *next;
	hb_blob_t *blob;
	unsigned int tag;
	} hb_graphite2_tablelist_t;

	struct hb_graphite2_face_data_t
	{
	hb_face_t *face;
	gr_face *grface;
	hb_atomic_ptr_t<hb_graphite2_tablelist_t> tlist;
	};

	static const void hb_graphite2_get_table (const void data, unsigned int tag, size_t *len)
	{
	hb_graphite2_face_data_t face_data = (hb_graphite2_face_data_t ) data;
	hb_graphite2_tablelist_t *tlist = face_data->tlist;

	hb_blob_t *blob = nullptr;

	for (hb_graphite2_tablelist_t *p = tlist; p; p = p->next)
	if (p->tag == tag) {
	blob = p->blob;
	break;
	}

	if (unlikely (!blob))
	{
	blob = face_data->face->reference_table (tag);

	hb_graphite2_tablelist_t p = (hb_graphite2_tablelist_t ) hb_calloc (1, sizeof (hb_graphite2_tablelist_t));
	if (unlikely (!p)) {
	hb_blob_destroy (blob);
	return nullptr;
	}
	p->blob = blob;
	p->tag = tag;

	retry:
	hb_graphite2_tablelist_t *tlist = face_data->tlist;
	p->next = tlist;

	if (unlikely (!face_data->tlist.cmpexch (tlist, p)))
	goto retry;
	}

	unsigned int tlen;
	const char *d = hb_blob_get_data (blob, &tlen);
	*len = tlen;
	return d;
	}

	hb_graphite2_face_data_t *
	_hb_graphite2_shaper_face_data_create (hb_face_t *face)
	{
	hb_blob_t *silf_blob = face->reference_table (HB_GRAPHITE2_TAG_SILF);
	/* Umm, we just reference the table to check whether it exists.
	* Maybe add better API for this? */
	if (!hb_blob_get_length (silf_blob))
	{
	hb_blob_destroy (silf_blob);
	return nullptr;
	}
	hb_blob_destroy (silf_blob);

	hb_graphite2_face_data_t data = (hb_graphite2_face_data_t ) hb_calloc (1, sizeof (hb_graphite2_face_data_t));
	if (unlikely (!data))
	return nullptr;

	data->face = face;
	const gr_face_ops ops = {sizeof(gr_face_ops), &hb_graphite2_get_table, NULL};
	data->grface = gr_make_face_with_ops (data, &ops, gr_face_preloadAll);

	if (unlikely (!data->grface)) {
	hb_free (data);
	return nullptr;
	}

	return data;
	}

	void
	_hb_graphite2_shaper_face_data_destroy (hb_graphite2_face_data_t *data)
	{
	hb_graphite2_tablelist_t *tlist = data->tlist;

	while (tlist)
	{
	hb_graphite2_tablelist_t *old = tlist;
	hb_blob_destroy (tlist->blob);
	tlist = tlist->next;
	hb_free (old);
	}

	gr_face_destroy (data->grface);

	hb_free (data);
	}

	/**
	* hb_graphite2_face_get_gr_face: (skip)
	* @face: @hb_face_t to query
	*
	* Fetches the Graphite2 gr_face corresponding to the specified
	* #hb_face_t face object.
	*
	* Return value: the gr_face found
	*
	* Since: 0.9.10
	*/
	gr_face *
	hb_graphite2_face_get_gr_face (hb_face_t *face)
	{
	const hb_graphite2_face_data_t *data = face->data.graphite2;
	return data ? data->grface : nullptr;
	}


	/*
	* shaper font data
	*/

	struct hb_graphite2_font_data_t {};

	hb_graphite2_font_data_t *
	_hb_graphite2_shaper_font_data_create (hb_font_t *font HB_UNUSED)
	{
	return (hb_graphite2_font_data_t *) HB_SHAPER_DATA_SUCCEEDED;
	}

	void
	_hb_graphite2_shaper_font_data_destroy (hb_graphite2_font_data_t *data HB_UNUSED)
	{
	}

	#ifndef HB_DISABLE_DEPRECATED
	/**
	* hb_graphite2_font_get_gr_font: (skip)
	* @font: An #hb_font_t
	*
	* Always returns `NULL`. Use hb_graphite2_face_get_gr_face() instead.
	*
	* Return value: (nullable): Graphite2 font associated with @font.
	*
	* Since: 0.9.10
	* Deprecated: 1.4.2
	*/
	gr_font *
	hb_graphite2_font_get_gr_font (hb_font_t *font HB_UNUSED)
	{
	return nullptr;
	}
	#endif


	/*
	* shaper
	*/

	struct hb_graphite2_cluster_t {
	unsigned int base_char;
	unsigned int num_chars;
	unsigned int base_glyph;
	unsigned int num_glyphs;
	unsigned int cluster;
	int advance;
	};

	hb_bool_t
	_hb_graphite2_shape (hb_shape_plan_t *shape_plan HB_UNUSED,
	hb_font_t *font,
	hb_buffer_t *buffer,
	const hb_feature_t *features,
	unsigned int num_features)
	{
	hb_face_t *face = font->face;
	gr_face *grface = face->data.graphite2->grface;

	const char *lang = hb_language_to_string (hb_buffer_get_language (buffer));
	const char *lang_end = lang ? strchr (lang, '-') : nullptr;
	int lang_len = lang_end ? lang_end - lang : -1;
	gr_feature_val *feats = gr_face_featureval_for_lang (grface, lang ? hb_tag_from_string (lang, lang_len) : 0);

	for (unsigned int i = 0; i < num_features; i++)
	{
	const gr_feature_ref *fref = gr_face_find_fref (grface, features[i].tag);
	if (fref)
	gr_fref_set_feature_value (fref, features[i].value, feats);
	}

	hb_direction_t direction = buffer->props.direction;
	hb_direction_t horiz_dir = hb_script_get_horizontal_direction (buffer->props.script);
	/* TODO vertical:
	* The only BTT vertical script is Ogham, but it's not clear to me whether OpenType
	* Ogham fonts are supposed to be implemented BTT or not. Need to research that
	* first. */
	if ((HB_DIRECTION_IS_HORIZONTAL (direction) &&
	direction != horiz_dir && horiz_dir != HB_DIRECTION_INVALID) \|\|
	(HB_DIRECTION_IS_VERTICAL (direction) &&
	direction != HB_DIRECTION_TTB))
	{
	hb_buffer_reverse_clusters (buffer);
	direction = HB_DIRECTION_REVERSE (direction);
	}

	gr_segment *seg = nullptr;
	const gr_slot *is;
	unsigned int ci = 0, ic = 0;
	unsigned int curradvx = 0, curradvy = 0;

	unsigned int scratch_size;
	hb_buffer_t::scratch_buffer_t *scratch = buffer->get_scratch_buffer (&scratch_size);

	uint32_t chars = (uint32_t ) scratch;

	for (unsigned int i = 0; i < buffer->len; ++i)
	chars[i] = buffer->info[i].codepoint;

	seg = gr_make_seg (nullptr, grface,
	HB_TAG_NONE, // https://github.com/harfbuzz/harfbuzz/issues/3439#issuecomment-1442650148
	feats,
	gr_utf32, chars, buffer->len,
	2 \| (direction == HB_DIRECTION_RTL ? 1 : 0));

	if (unlikely (!seg)) {
	if (feats) gr_featureval_destroy (feats);
	return false;
	}

	unsigned int glyph_count = gr_seg_n_slots (seg);
	if (unlikely (!glyph_count)) {
	if (feats) gr_featureval_destroy (feats);
	gr_seg_destroy (seg);
	buffer->len = 0;
	return true;
	}

	(void) buffer->ensure (glyph_count);
	scratch = buffer->get_scratch_buffer (&scratch_size);
	while ((DIV_CEIL (sizeof (hb_graphite2_cluster_t) * buffer->len, sizeof (*scratch)) +
	DIV_CEIL (sizeof (hb_codepoint_t) * glyph_count, sizeof (*scratch))) > scratch_size)
	{
	if (unlikely (!buffer->ensure (buffer->allocated * 2)))
	{
	if (feats) gr_featureval_destroy (feats);
	gr_seg_destroy (seg);
	return false;
	}
	scratch = buffer->get_scratch_buffer (&scratch_size);
	}

	#define ALLOCATE_ARRAY(Type, name, len) \
	Type name = (Type ) scratch; \
	do { \
	unsigned int _consumed = DIV_CEIL ((len) * sizeof (Type), sizeof (*scratch)); \
	assert (_consumed <= scratch_size); \
	scratch += _consumed; \
	scratch_size -= _consumed; \
	} while (0)

	ALLOCATE_ARRAY (hb_graphite2_cluster_t, clusters, buffer->len);
	ALLOCATE_ARRAY (hb_codepoint_t, gids, glyph_count);

	#undef ALLOCATE_ARRAY

	hb_memset (clusters, 0, sizeof (clusters[0]) * buffer->len);

	hb_codepoint_t *pg = gids;
	clusters[0].cluster = buffer->info[0].cluster;
	unsigned int upem = hb_face_get_upem (face);
	float xscale = (float) font->x_scale / upem;
	float yscale = (float) font->y_scale / upem;
	yscale *= yscale / xscale;
	unsigned int curradv = 0;
	if (HB_DIRECTION_IS_BACKWARD (direction))
	{
	curradv = gr_slot_origin_X(gr_seg_first_slot(seg)) * xscale;
	clusters[0].advance = gr_seg_advance_X(seg) * xscale - curradv;
	}
	else
	clusters[0].advance = 0;
	for (is = gr_seg_first_slot (seg), ic = 0; is; is = gr_slot_next_in_segment (is), ic++)
	{
	unsigned int before = gr_slot_before (is);
	unsigned int after = gr_slot_after (is);
	*pg = gr_slot_gid (is);
	pg++;
	while (clusters[ci].base_char > before && ci)
	{
	clusters[ci-1].num_chars += clusters[ci].num_chars;
	clusters[ci-1].num_glyphs += clusters[ci].num_glyphs;
	clusters[ci-1].advance += clusters[ci].advance;
	ci--;
	}

	if (gr_slot_can_insert_before (is) && clusters[ci].num_chars && before >= clusters[ci].base_char + clusters[ci].num_chars)
	{
	hb_graphite2_cluster_t *c = clusters + ci + 1;
	c->base_char = clusters[ci].base_char + clusters[ci].num_chars;
	c->cluster = buffer->info[c->base_char].cluster;
	c->num_chars = before - c->base_char;
	c->base_glyph = ic;
	c->num_glyphs = 0;
	if (HB_DIRECTION_IS_BACKWARD (direction))
	{
	c->advance = curradv - gr_slot_origin_X(is) * xscale;
	curradv -= c->advance;
	}
	else
	{
	auto origin_X = gr_slot_origin_X (is) * xscale;
	c->advance = 0;
	clusters[ci].advance += origin_X - curradv;
	curradv = origin_X;
	}
	ci++;
	}
	clusters[ci].num_glyphs++;

	if (clusters[ci].base_char + clusters[ci].num_chars < after + 1)
	clusters[ci].num_chars = after + 1 - clusters[ci].base_char;
	}

	if (HB_DIRECTION_IS_BACKWARD (direction))
	clusters[ci].advance += curradv;
	else
	clusters[ci].advance += gr_seg_advance_X(seg) * xscale - curradv;
	ci++;

	for (unsigned int i = 0; i < ci; ++i)
	{
	for (unsigned int j = 0; j < clusters[i].num_glyphs; ++j)
	{
	hb_glyph_info_t *info = &buffer->info[clusters[i].base_glyph + j];
	info->codepoint = gids[clusters[i].base_glyph + j];
	info->cluster = clusters[i].cluster;
	info->var1.i32 = clusters[i].advance; // all glyphs in the cluster get the same advance
	}
	}
	buffer->len = glyph_count;

	/* Positioning. */
	unsigned int currclus = UINT_MAX;
	const hb_glyph_info_t *info = buffer->info;
	hb_glyph_position_t *pPos = hb_buffer_get_glyph_positions (buffer, nullptr);
	if (!HB_DIRECTION_IS_BACKWARD (direction))
	{
	curradvx = 0;
	for (is = gr_seg_first_slot (seg); is; pPos++, ++info, is = gr_slot_next_in_segment (is))
	{
	pPos->x_offset = gr_slot_origin_X (is) * xscale - curradvx;
	pPos->y_offset = gr_slot_origin_Y (is) * yscale - curradvy;
	if (info->cluster != currclus) {
	pPos->x_advance = info->var1.i32;
	curradvx += pPos->x_advance;
	currclus = info->cluster;
	} else
	pPos->x_advance = 0.;

	pPos->y_advance = gr_slot_advance_Y (is, grface, nullptr) * yscale;
	curradvy += pPos->y_advance;
	}
	}
	else
	{
	curradvx = gr_seg_advance_X(seg) * xscale;
	for (is = gr_seg_first_slot (seg); is; pPos++, info++, is = gr_slot_next_in_segment (is))
	{
	if (info->cluster != currclus)
	{
	pPos->x_advance = info->var1.i32;
	curradvx -= pPos->x_advance;
	currclus = info->cluster;
	} else
	pPos->x_advance = 0.;

	pPos->y_advance = gr_slot_advance_Y (is, grface, nullptr) * yscale;
	curradvy -= pPos->y_advance;
	pPos->x_offset = gr_slot_origin_X (is) * xscale - info->var1.i32 - curradvx + pPos->x_advance;
	pPos->y_offset = gr_slot_origin_Y (is) * yscale - curradvy;
	}
	hb_buffer_reverse_clusters (buffer);
	}

	if (feats) gr_featureval_destroy (feats);
	gr_seg_destroy (seg);

	buffer->clear_glyph_flags ();
	buffer->unsafe_to_break ();

	return true;
	}


	#endif