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 /*

  * Copyright © 2009,2010  Red Hat, Inc.

  * Copyright © 2010,2011,2012  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.

  *

  * Red Hat Author(s): Behdad Esfahbod

  * Google Author(s): Behdad Esfahbod

  */

 #define HB_SHAPER ot

 #define hb_ot_shaper_face_data_t hb_ot_layout_t

 #define hb_ot_shaper_shape_plan_data_t hb_ot_shape_plan_t

 #include "hb-shaper-impl-private.hh"

 #include "hb-ot-shape-private.hh"

 #include "hb-ot-shape-complex-private.hh"

 #include "hb-ot-shape-fallback-private.hh"

 #include "hb-ot-shape-normalize-private.hh"

 #include "hb-ot-layout-private.hh"

 #include "hb-set-private.hh"

 static hb_tag_t common_features[] = {

   HB_TAG('c','c','m','p'),

   HB_TAG('l','i','g','a'),

   HB_TAG('l','o','c','l'),

   HB_TAG('m','a','r','k'),

   HB_TAG('m','k','m','k'),

   HB_TAG('r','l','i','g'),

 };

 static hb_tag_t horizontal_features[] = {

   HB_TAG('c','a','l','t'),

   HB_TAG('c','l','i','g'),

   HB_TAG('c','u','r','s'),

   HB_TAG('k','e','r','n'),

   HB_TAG('r','c','l','t'),

 };

 static hb_tag_t vertical_features[] = {

   HB_TAG('v','e','r','t'),

 };

 static void

 hb_ot_shape_collect_features (hb_ot_shape_planner_t          *planner,

 			      const hb_segment_properties_t  *props,

 			      const hb_feature_t             *user_features,

 			      unsigned int                    num_user_features)

 {

   hb_ot_map_builder_t *map = &planner->map;

   switch (props->direction) {

     case HB_DIRECTION_LTR:

       map->add_global_bool_feature (HB_TAG ('l','t','r','a'));

       map->add_global_bool_feature (HB_TAG ('l','t','r','m'));

       break;

     case HB_DIRECTION_RTL:

       map->add_global_bool_feature (HB_TAG ('r','t','l','a'));

       map->add_feature (HB_TAG ('r','t','l','m'), 1, F_NONE);

       break;

     case HB_DIRECTION_TTB:

     case HB_DIRECTION_BTT:

     case HB_DIRECTION_INVALID:

     default:

       break;

   }

   map->add_feature (HB_TAG ('f','r','a','c'), 1, F_NONE);

   map->add_feature (HB_TAG ('n','u','m','r'), 1, F_NONE);

   map->add_feature (HB_TAG ('d','n','o','m'), 1, F_NONE);

   if (planner->shaper->collect_features)

     planner->shaper->collect_features (planner);

   for (unsigned int i = 0; i < ARRAY_LENGTH (common_features); i++)

     map->add_global_bool_feature (common_features[i]);

   if (HB_DIRECTION_IS_HORIZONTAL (props->direction))

     for (unsigned int i = 0; i < ARRAY_LENGTH (horizontal_features); i++)

       map->add_feature (horizontal_features[i], 1, F_GLOBAL |

 			(horizontal_features[i] == HB_TAG('k','e','r','n') ?

 			 F_HAS_FALLBACK : F_NONE));

   else

     for (unsigned int i = 0; i < ARRAY_LENGTH (vertical_features); i++)

       map->add_feature (vertical_features[i], 1, F_GLOBAL |

 			(vertical_features[i] == HB_TAG('v','k','r','n') ?

 			 F_HAS_FALLBACK : F_NONE));

   if (planner->shaper->override_features)

     planner->shaper->override_features (planner);

   for (unsigned int i = 0; i < num_user_features; i++) {

     const hb_feature_t *feature = &user_features[i];

     map->add_feature (feature->tag, feature->value,

 		      (feature->start == 0 && feature->end == (unsigned int) -1) ?

 		       F_GLOBAL : F_NONE);

   }

 }

 /*

  * shaper face data

  */

 hb_ot_shaper_face_data_t *

 _hb_ot_shaper_face_data_create (hb_face_t *face)

 {

   return _hb_ot_layout_create (face);

 }

 void

 _hb_ot_shaper_face_data_destroy (hb_ot_shaper_face_data_t *data)

 {

   _hb_ot_layout_destroy (data);

 }

 /*

  * shaper font data

  */

 struct hb_ot_shaper_font_data_t {};

 hb_ot_shaper_font_data_t *

 _hb_ot_shaper_font_data_create (hb_font_t *font)

 {

   return (hb_ot_shaper_font_data_t *) HB_SHAPER_DATA_SUCCEEDED;

 }

 void

 _hb_ot_shaper_font_data_destroy (hb_ot_shaper_font_data_t *data)

 {

 }

 /*

  * shaper shape_plan data

  */

 hb_ot_shaper_shape_plan_data_t *

 _hb_ot_shaper_shape_plan_data_create (hb_shape_plan_t    *shape_plan,

 				      const hb_feature_t *user_features,

 				      unsigned int        num_user_features)

 {

   hb_ot_shape_plan_t *plan = (hb_ot_shape_plan_t *) calloc (1, sizeof (hb_ot_shape_plan_t));

   if (unlikely (!plan))

     return NULL;

   hb_ot_shape_planner_t planner (shape_plan);

   planner.shaper = hb_ot_shape_complex_categorize (&planner);

   hb_ot_shape_collect_features (&planner, &shape_plan->props, user_features, num_user_features);

   planner.compile (*plan);

   if (plan->shaper->data_create) {

     plan->data = plan->shaper->data_create (plan);

     if (unlikely (!plan->data))

       return NULL;

   }

   return plan;

 }

 void

 _hb_ot_shaper_shape_plan_data_destroy (hb_ot_shaper_shape_plan_data_t *plan)

 {

   if (plan->shaper->data_destroy)

     plan->shaper->data_destroy (const_cast<void *> (plan->data));

   plan->finish ();

   free (plan);

 }

 /*

  * shaper

  */

 struct hb_ot_shape_context_t

 {

   hb_ot_shape_plan_t *plan;

   hb_font_t *font;

   hb_face_t *face;

   hb_buffer_t  *buffer;

   const hb_feature_t *user_features;

   unsigned int        num_user_features;

   /* Transient stuff */

   hb_direction_t target_direction;

 };

 /* Main shaper */

 /* Prepare */

 static void

 hb_set_unicode_props (hb_buffer_t *buffer)

 {

   unsigned int count = buffer->len;

   for (unsigned int i = 0; i < count; i++)

     _hb_glyph_info_set_unicode_props (&buffer->info[i], buffer->unicode);

 }

 static void

 hb_insert_dotted_circle (hb_buffer_t *buffer, hb_font_t *font)

 {

   if (!(buffer->flags & HB_BUFFER_FLAG_BOT) ||

       _hb_glyph_info_get_general_category (&buffer->info[0]) !=

       HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)

     return;

   if (!font->has_glyph (0x25CC))

     return;

   hb_glyph_info_t dottedcircle;

   dottedcircle.codepoint = 0x25CC;

   _hb_glyph_info_set_unicode_props (&dottedcircle, buffer->unicode);

   buffer->clear_output ();

   buffer->idx = 0;

   hb_glyph_info_t info = dottedcircle;

   info.cluster = buffer->cur().cluster;

   info.mask = buffer->cur().mask;

   buffer->output_info (info);

   while (buffer->idx < buffer->len)

     buffer->next_glyph ();

   buffer->swap_buffers ();

 }

 static void

 hb_form_clusters (hb_buffer_t *buffer)

 {

   unsigned int count = buffer->len;

   for (unsigned int i = 1; i < count; i++)

     if (HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->info[i])))

       buffer->merge_clusters (i - 1, i + 1);

 }

 static void

 hb_ensure_native_direction (hb_buffer_t *buffer)

 {

   hb_direction_t direction = buffer->props.direction;

   /* 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 != hb_script_get_horizontal_direction (buffer->props.script)) ||

       (HB_DIRECTION_IS_VERTICAL   (direction) && direction != HB_DIRECTION_TTB))

   {

     hb_buffer_reverse_clusters (buffer);

     buffer->props.direction = HB_DIRECTION_REVERSE (buffer->props.direction);

   }

 }

 /* Substitute */

 static inline void

 hb_ot_mirror_chars (hb_ot_shape_context_t *c)

 {

   if (HB_DIRECTION_IS_FORWARD (c->target_direction))

     return;

   hb_buffer_t *buffer = c->buffer;

   hb_unicode_funcs_t *unicode = buffer->unicode;

   hb_mask_t rtlm_mask = c->plan->rtlm_mask;

   unsigned int count = buffer->len;

   hb_glyph_info_t *info = buffer->info;

   for (unsigned int i = 0; i < count; i++) {

     hb_codepoint_t codepoint = unicode->mirroring (info[i].codepoint);

     if (likely (codepoint == info[i].codepoint))

       info[i].mask |= rtlm_mask;

     else

       info[i].codepoint = codepoint;

   }

 }

 static inline void

 hb_ot_shape_setup_masks_fraction (hb_ot_shape_context_t *c)

 {

   if (!c->plan->has_frac)

     return;

   hb_buffer_t *buffer = c->buffer;

   /* TODO look in pre/post context text also. */

   unsigned int count = buffer->len;

   hb_glyph_info_t *info = buffer->info;

   for (unsigned int i = 0; i < count; i++)

   {

     if (info[i].codepoint == 0x2044) /* FRACTION SLASH */

     {

       unsigned int start = i, end = i + 1;

       while (start &&

 	     _hb_glyph_info_get_general_category (&info[start - 1]) ==

 	     HB_UNICODE_GENERAL_CATEGORY_DECIMAL_NUMBER)

         start--;

       while (end < count &&

 	     _hb_glyph_info_get_general_category (&info[end]) ==

 	     HB_UNICODE_GENERAL_CATEGORY_DECIMAL_NUMBER)

         end++;

       for (unsigned int j = start; j < i; j++)

         info[j].mask |= c->plan->numr_mask | c->plan->frac_mask;

       info[i].mask |= c->plan->frac_mask;

       for (unsigned int j = i + 1; j < end; j++)

         info[j].mask |= c->plan->frac_mask | c->plan->dnom_mask;

       i = end - 1;

     }

   }

 }

 static inline void

 hb_ot_shape_initialize_masks (hb_ot_shape_context_t *c)

 {

   hb_ot_map_t *map = &c->plan->map;

   hb_buffer_t *buffer = c->buffer;

   hb_mask_t global_mask = map->get_global_mask ();

   buffer->reset_masks (global_mask);

 }

 static inline void

 hb_ot_shape_setup_masks (hb_ot_shape_context_t *c)

 {

   hb_ot_map_t *map = &c->plan->map;

   hb_buffer_t *buffer = c->buffer;

   hb_ot_shape_setup_masks_fraction (c);

   if (c->plan->shaper->setup_masks)

     c->plan->shaper->setup_masks (c->plan, buffer, c->font);

   for (unsigned int i = 0; i < c->num_user_features; i++)

   {

     const hb_feature_t *feature = &c->user_features[i];

     if (!(feature->start == 0 && feature->end == (unsigned int)-1)) {

       unsigned int shift;

       hb_mask_t mask = map->get_mask (feature->tag, &shift);

       buffer->set_masks (feature->value << shift, mask, feature->start, feature->end);

     }

   }

 }

 static inline void

 hb_ot_map_glyphs_fast (hb_buffer_t  *buffer)

 {

   /* Normalization process sets up glyph_index(), we just copy it. */

   unsigned int count = buffer->len;

   for (unsigned int i = 0; i < count; i++)

     buffer->info[i].codepoint = buffer->info[i].glyph_index();

 }

 static inline void

 hb_synthesize_glyph_classes (hb_ot_shape_context_t *c)

 {

   unsigned int count = c->buffer->len;

   hb_glyph_info_t *info = c->buffer->info;

   for (unsigned int i = 0; i < count; i++)

     _hb_glyph_info_set_glyph_props (&info[i],

 				    _hb_glyph_info_get_general_category (&info[i])

 				    == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK ?

 				    HB_OT_LAYOUT_GLYPH_PROPS_MARK :

 				    HB_OT_LAYOUT_GLYPH_PROPS_BASE_GLYPH);

 }

 static inline void

 hb_ot_substitute_default (hb_ot_shape_context_t *c)

 {

   hb_buffer_t *buffer = c->buffer;

   if (c->plan->shaper->preprocess_text)

     c->plan->shaper->preprocess_text (c->plan, buffer, c->font);

   hb_ot_shape_initialize_masks (c);

   hb_ot_mirror_chars (c);

   HB_BUFFER_ALLOCATE_VAR (buffer, glyph_index);

   _hb_ot_shape_normalize (c->plan, buffer, c->font);

   hb_ot_shape_setup_masks (c);

   /* This is unfortunate to go here, but necessary... */

   if (!hb_ot_layout_has_positioning (c->face))

     _hb_ot_shape_fallback_position_recategorize_marks (c->plan, c->font, buffer);

   hb_ot_map_glyphs_fast (buffer);

   HB_BUFFER_DEALLOCATE_VAR (buffer, glyph_index);

 }

 static inline void

 hb_ot_substitute_complex (hb_ot_shape_context_t *c)

 {

   hb_buffer_t *buffer = c->buffer;

   hb_ot_layout_substitute_start (c->font, buffer);

   if (!hb_ot_layout_has_glyph_classes (c->face))

     hb_synthesize_glyph_classes (c);

   c->plan->substitute (c->font, buffer);

   hb_ot_layout_substitute_finish (c->font, buffer);

   return;

 }

 static inline void

 hb_ot_substitute (hb_ot_shape_context_t *c)

 {

   hb_ot_substitute_default (c);

   hb_ot_substitute_complex (c);

 }

 /* Position */

 static inline void

 zero_mark_widths_by_unicode (hb_buffer_t *buffer)

 {

   unsigned int count = buffer->len;

   for (unsigned int i = 0; i < count; i++)

     if (_hb_glyph_info_get_general_category (&buffer->info[i]) == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)

     {

       buffer->pos[i].x_advance = 0;

       buffer->pos[i].y_advance = 0;

     }

 }

 static inline void

 zero_mark_widths_by_gdef (hb_buffer_t *buffer)

 {

   unsigned int count = buffer->len;

   for (unsigned int i = 0; i < count; i++)

     if (_hb_glyph_info_is_mark (&buffer->info[i]))

     {

       buffer->pos[i].x_advance = 0;

       buffer->pos[i].y_advance = 0;

     }

 }

 static inline void

 hb_ot_position_default (hb_ot_shape_context_t *c)

 {

   hb_direction_t direction = c->buffer->props.direction;

   unsigned int count = c->buffer->len;

   hb_glyph_info_t *info = c->buffer->info;

   hb_glyph_position_t *pos = c->buffer->pos;

   for (unsigned int i = 0; i < count; i++)

   {

     c->font->get_glyph_advance_for_direction (info[i].codepoint,

 					      direction,

 					      &pos[i].x_advance,

 					      &pos[i].y_advance);

     c->font->subtract_glyph_origin_for_direction (info[i].codepoint,

 						  direction,

 						  &pos[i].x_offset,

 						  &pos[i].y_offset);

   }

 }

 static inline bool

 hb_ot_position_complex (hb_ot_shape_context_t *c)

 {

   bool ret = false;

   unsigned int count = c->buffer->len;

   switch (c->plan->shaper->zero_width_marks)

   {

     case HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_GDEF_EARLY:

       zero_mark_widths_by_gdef (c->buffer);

       break;

     /* Not currently used for any shaper:

     case HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_UNICODE_EARLY:

       zero_mark_widths_by_unicode (c->buffer);

       break;

     */

     default:

     case HB_OT_SHAPE_ZERO_WIDTH_MARKS_NONE:

     case HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_UNICODE_LATE:

     case HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_GDEF_LATE:

       break;

   }

   if (hb_ot_layout_has_positioning (c->face))

   {

     hb_glyph_info_t *info = c->buffer->info;

     hb_glyph_position_t *pos = c->buffer->pos;

     /* Change glyph origin to what GPOS expects, apply GPOS, change it back. */

     for (unsigned int i = 0; i < count; i++) {

       c->font->add_glyph_origin_for_direction (info[i].codepoint,

 					       HB_DIRECTION_LTR,

 					       &pos[i].x_offset,

 					       &pos[i].y_offset);

     }

     c->plan->position (c->font, c->buffer);

     for (unsigned int i = 0; i < count; i++) {

       c->font->subtract_glyph_origin_for_direction (info[i].codepoint,

 						    HB_DIRECTION_LTR,

 						    &pos[i].x_offset,

 						    &pos[i].y_offset);

     }

     ret = true;

   }

   switch (c->plan->shaper->zero_width_marks)

   {

     case HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_UNICODE_LATE:

       zero_mark_widths_by_unicode (c->buffer);

       break;

     case HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_GDEF_LATE:

       zero_mark_widths_by_gdef (c->buffer);

       break;

     default:

     case HB_OT_SHAPE_ZERO_WIDTH_MARKS_NONE:

     //case HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_UNICODE_EARLY:

     case HB_OT_SHAPE_ZERO_WIDTH_MARKS_BY_GDEF_EARLY:

       break;

   }

   return ret;

 }

 static inline void

 hb_ot_position (hb_ot_shape_context_t *c)

 {

   hb_ot_layout_position_start (c->font, c->buffer);

   hb_ot_position_default (c);

   hb_bool_t fallback = !hb_ot_position_complex (c);

   hb_ot_layout_position_finish (c->font, c->buffer);

   if (fallback && c->plan->shaper->fallback_position)

     _hb_ot_shape_fallback_position (c->plan, c->font, c->buffer);

   if (HB_DIRECTION_IS_BACKWARD (c->buffer->props.direction))

     hb_buffer_reverse (c->buffer);

   /* Visual fallback goes here. */

   if (fallback)

     _hb_ot_shape_fallback_kern (c->plan, c->font, c->buffer);

 }

 /* Post-process */

 static void

 hb_ot_hide_default_ignorables (hb_ot_shape_context_t *c)

 {

   if (c->buffer->flags & HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES)

     return;

   hb_codepoint_t space;

   enum {

     SPACE_DONT_KNOW,

     SPACE_AVAILABLE,

     SPACE_UNAVAILABLE

   } space_status = SPACE_DONT_KNOW;

   unsigned int count = c->buffer->len;

   hb_glyph_info_t *info = c->buffer->info;

   hb_glyph_position_t *pos = c->buffer->pos;

   unsigned int j = 0;

   for (unsigned int i = 0; i < count; i++)

   {

     if (unlikely (!_hb_glyph_info_ligated (&info[i]) &&

 		  _hb_glyph_info_is_default_ignorable (&info[i])))

     {

       if (space_status == SPACE_DONT_KNOW)

 	space_status = c->font->get_glyph (' ', 0, &space) ? SPACE_AVAILABLE : SPACE_UNAVAILABLE;

       if (space_status == SPACE_AVAILABLE)

       {

 	info[i].codepoint = space;

 	pos[i].x_advance = 0;

 	pos[i].y_advance = 0;

       }

       else

 	continue; /* Delete it. */

     }

     if (j != i)

     {

       info[j] = info[i];

       pos[j] = pos[i];

     }

     j++;

   }

   c->buffer->len = j;

 }

 /* Pull it all together! */

 static void

 hb_ot_shape_internal (hb_ot_shape_context_t *c)

 {

   c->buffer->deallocate_var_all ();

   /* Save the original direction, we use it later. */

   c->target_direction = c->buffer->props.direction;

   _hb_buffer_allocate_unicode_vars (c->buffer);

   c->buffer->clear_output ();

   hb_set_unicode_props (c->buffer);

   hb_insert_dotted_circle (c->buffer, c->font);

   hb_form_clusters (c->buffer);

   hb_ensure_native_direction (c->buffer);

   hb_ot_substitute (c);

   hb_ot_position (c);

   hb_ot_hide_default_ignorables (c);

   _hb_buffer_deallocate_unicode_vars (c->buffer);

   c->buffer->props.direction = c->target_direction;

   c->buffer->deallocate_var_all ();

 }

 hb_bool_t

 _hb_ot_shape (hb_shape_plan_t    *shape_plan,

 	      hb_font_t          *font,

 	      hb_buffer_t        *buffer,

 	      const hb_feature_t *features,

 	      unsigned int        num_features)

 {

   hb_ot_shape_context_t c = {HB_SHAPER_DATA_GET (shape_plan), font, font->face, buffer, features, num_features};

   hb_ot_shape_internal (&c);

   return true;

 }

 void

 hb_ot_shape_plan_collect_lookups (hb_shape_plan_t *shape_plan,

 				  hb_tag_t         table_tag,

 				  hb_set_t        *lookup_indexes /* OUT */)

 {

   /* XXX Does the first part always succeed? */

   HB_SHAPER_DATA_GET (shape_plan)->collect_lookups (table_tag, lookup_indexes);

 }

 /* TODO Move this to hb-ot-shape-normalize, make it do decompose, and make it public. */

 static void

 add_char (hb_font_t          *font,

 	  hb_unicode_funcs_t *unicode,

 	  hb_bool_t           mirror,

 	  hb_codepoint_t      u,

 	  hb_set_t           *glyphs)

 {

   hb_codepoint_t glyph;

   if (font->get_glyph (u, 0, &glyph))

     glyphs->add (glyph);

   if (mirror)

   {

     hb_codepoint_t m = unicode->mirroring (u);

     if (m != u && font->get_glyph (m, 0, &glyph))

       glyphs->add (glyph);

   }

 }

 void

 hb_ot_shape_glyphs_closure (hb_font_t          *font,

 			    hb_buffer_t        *buffer,

 			    const hb_feature_t *features,

 			    unsigned int        num_features,

 			    hb_set_t           *glyphs)

 {

   hb_ot_shape_plan_t plan;

   const char *shapers[] = {"ot", NULL};

   hb_shape_plan_t *shape_plan = hb_shape_plan_create_cached (font->face, &buffer->props,

 							     features, num_features, shapers);

   bool mirror = hb_script_get_horizontal_direction (buffer->props.script) == HB_DIRECTION_RTL;

   unsigned int count = buffer->len;

   for (unsigned int i = 0; i < count; i++)

     add_char (font, buffer->unicode, mirror, buffer->info[i].codepoint, glyphs);

   hb_set_t lookups;

   lookups.init ();

   hb_ot_shape_plan_collect_lookups (shape_plan, HB_OT_TAG_GSUB, &lookups);

   /* And find transitive closure. */

   hb_set_t copy;

   copy.init ();

   do {

     copy.set (glyphs);

     for (hb_codepoint_t lookup_index = -1; hb_set_next (&lookups, &lookup_index);)

       hb_ot_layout_lookup_substitute_closure (font->face, lookup_index, glyphs);

   } while (!copy.is_equal (glyphs));

   hb_shape_plan_destroy (shape_plan);

 }