src/hb-ot-shape.cc - third_party/harfbuzz - Git at Google

 /*
  * Copyright © 2009,2010  Red Hat, Inc.
  * Copyright © 2010  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
  */

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

 #include "hb-font-private.hh"

 HB_BEGIN_DECLS


 /* XXX vertical */
 hb_tag_t default_features[] = {
   HB_TAG('c','a','l','t'),
   HB_TAG('c','c','m','p'),
   HB_TAG('c','l','i','g'),
   HB_TAG('c','u','r','s'),
   HB_TAG('k','e','r','n'),
   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 void
 hb_ot_shape_collect_features (hb_ot_shape_plan_t       *plan,
 			      const hb_segment_properties_t  *props,
 			      const hb_feature_t       *user_features,
 			      unsigned int              num_user_features)
 {
   switch (props->direction) {
     case HB_DIRECTION_LTR:
       plan->map.add_bool_feature (HB_TAG ('l','t','r','a'));
       plan->map.add_bool_feature (HB_TAG ('l','t','r','m'));
       break;
     case HB_DIRECTION_RTL:
       plan->map.add_bool_feature (HB_TAG ('r','t','l','a'));
       plan->map.add_bool_feature (HB_TAG ('r','t','l','m'), false);
       break;
     case HB_DIRECTION_TTB:
     case HB_DIRECTION_BTT:
     case HB_DIRECTION_INVALID:
     default:
       break;
   }

   for (unsigned int i = 0; i < ARRAY_LENGTH (default_features); i++)
     plan->map.add_bool_feature (default_features[i]);

   hb_ot_shape_complex_collect_features (plan, props);

   for (unsigned int i = 0; i < num_user_features; i++) {
     const hb_feature_t *feature = &user_features[i];
     plan->map.add_feature (feature->tag, feature->value, (feature->start == 0 && feature->end == (unsigned int) -1));
   }
 }


 static void
 hb_ot_shape_setup_masks (hb_ot_shape_context_t *c)
 {
   hb_mask_t global_mask = c->plan->map.get_global_mask ();
   c->buffer->reset_masks (global_mask);

   hb_ot_shape_complex_setup_masks (c); /* BUFFER: Clobbers var2 */

   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 = c->plan->map.get_mask (feature->tag, &shift);
       c->buffer->set_masks (feature->value << shift, mask, feature->start, feature->end);
     }
   }
 }


 static void
 hb_ot_substitute_complex (hb_ot_shape_context_t *c)
 {
   if (!hb_ot_layout_has_substitution (c->face))
     return;

   c->plan->map.substitute (c->face, c->buffer);

   c->applied_substitute_complex = TRUE;
   return;
 }

 static void
 hb_ot_position_complex (hb_ot_shape_context_t *c)
 {

   if (!hb_ot_layout_has_positioning (c->face))
     return;

   unsigned int count = c->buffer->len;
   for (unsigned int i = 0; i < count; i++) {
     hb_font_add_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
 					    HB_DIRECTION_LTR,
 					    &c->buffer->pos[i].x_offset,
 					    &c->buffer->pos[i].y_offset);
   }

   c->plan->map.position (c->font, c->face, c->buffer);

   for (unsigned int i = 0; i < count; i++) {
     hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
 						 HB_DIRECTION_LTR,
 						 &c->buffer->pos[i].x_offset,
 						 &c->buffer->pos[i].y_offset);
   }

   hb_ot_layout_position_finish (c->buffer);

   c->applied_position_complex = TRUE;
   return;
 }


 /* Main shaper */

 /* Prepare */

 static inline hb_bool_t
 is_variation_selector (hb_codepoint_t unicode)
 {
   return unlikely ((unicode >=  0x180B && unicode <=  0x180D) || /* MONGOLIAN FREE VARIATION SELECTOR ONE..THREE */
 		   (unicode >=  0xFE00 && unicode <=  0xFE0F) || /* VARIATION SELECTOR-1..16 */
 		   (unicode >= 0xE0100 && unicode <= 0xE01EF));  /* VARIATION SELECTOR-17..256 */
 }

 static void
 hb_set_unicode_props (hb_ot_shape_context_t *c)
 {
   hb_unicode_funcs_t *unicode = c->buffer->unicode;
   hb_glyph_info_t *info = c->buffer->info;

   unsigned int count = c->buffer->len;
   for (unsigned int i = 1; i < count; i++) {
     info[i].general_category() = unicode->get_general_category (info[i].codepoint);
     info[i].combining_class() = unicode->get_combining_class (info[i].codepoint);
   }
 }

 static void
 hb_form_clusters (hb_ot_shape_context_t *c)
 {
   unsigned int count = c->buffer->len;
   for (unsigned int i = 1; i < count; i++)
     if (c->buffer->info[i].general_category() == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)
       c->buffer->info[i].cluster = c->buffer->info[i - 1].cluster;
 }

 static void
 hb_ensure_native_direction (hb_ot_shape_context_t *c)
 {
   hb_direction_t direction = c->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 (c->buffer->props.script)) ||
       (HB_DIRECTION_IS_VERTICAL   (direction) && direction != HB_DIRECTION_TTB))
   {
     hb_buffer_reverse_clusters (c->buffer);
     c->buffer->props.direction = HB_DIRECTION_REVERSE (c->buffer->props.direction);
   }
 }

 static void
 hb_reset_glyph_infos (hb_ot_shape_context_t *c)
 {
   unsigned int count = c->buffer->len;
   for (unsigned int i = 0; i < count; i++)
     c->buffer->info[i].var1.u32 = c->buffer->info[i].var2.u32 = 0;
 }


 /* Substitute */

 static void
 hb_mirror_chars (hb_ot_shape_context_t *c)
 {
   hb_unicode_funcs_t *unicode = c->buffer->unicode;

   if (HB_DIRECTION_IS_FORWARD (c->target_direction))
     return;

   hb_mask_t rtlm_mask = c->plan->map.get_1_mask (HB_TAG ('r','t','l','m'));

   unsigned int count = c->buffer->len;
   for (unsigned int i = 0; i < count; i++) {
     hb_codepoint_t codepoint = unicode->get_mirroring (c->buffer->info[i].codepoint);
     if (likely (codepoint == c->buffer->info[i].codepoint))
       c->buffer->info[i].mask |= rtlm_mask; /* XXX this should be moved to before setting user-feature masks */
     else
       c->buffer->info[i].codepoint = codepoint;
   }
 }

 static void
 hb_map_glyphs (hb_font_t    *font,
 	       hb_buffer_t  *buffer)
 {
   if (unlikely (!buffer->len))
     return;

   hb_codepoint_t glyph;
   buffer->clear_output ();
   unsigned int count = buffer->len - 1;
   for (buffer->i = 0; buffer->i < count;) {
     if (unlikely (is_variation_selector (buffer->info[buffer->i + 1].codepoint))) {
       hb_font_get_glyph (font, buffer->info[buffer->i].codepoint, buffer->info[buffer->i + 1].codepoint, &glyph);
       buffer->replace_glyph (glyph);
       buffer->i++;
     } else {
       hb_font_get_glyph (font, buffer->info[buffer->i].codepoint, 0, &glyph);
       buffer->replace_glyph (glyph);
     }
   }
   if (likely (buffer->i < buffer->len)) {
     hb_font_get_glyph (font, buffer->info[buffer->i].codepoint, 0, &glyph);
     buffer->replace_glyph (glyph);
   }
   buffer->swap ();
 }

 static void
 hb_substitute_default (hb_ot_shape_context_t *c)
 {
   hb_map_glyphs (c->font, c->buffer);
 }

 static void
 hb_substitute_complex_fallback (hb_ot_shape_context_t *c HB_UNUSED)
 {
   /* TODO Arabic */
 }


 /* Position */

 static void
 hb_position_default (hb_ot_shape_context_t *c)
 {
   hb_ot_layout_position_start (c->buffer);

   unsigned int count = c->buffer->len;
   for (unsigned int i = 0; i < count; i++) {
     hb_font_get_glyph_advance_for_direction (c->font, c->buffer->info[i].codepoint,
 					     c->buffer->props.direction,
 					     &c->buffer->pos[i].x_advance,
 					     &c->buffer->pos[i].y_advance);
     hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
 						 c->buffer->props.direction,
 						 &c->buffer->pos[i].x_offset,
 						 &c->buffer->pos[i].y_offset);
   }
 }

 static void
 hb_position_complex_fallback (hb_ot_shape_context_t *c HB_UNUSED)
 {
   /* TODO Mark pos */
 }

 static void
 hb_truetype_kern (hb_ot_shape_context_t *c)
 {
   /* TODO Check for kern=0 */
   unsigned int count = c->buffer->len;
   for (unsigned int i = 1; i < count; i++) {
     hb_position_t x_kern, y_kern, kern1, kern2;
     hb_font_get_glyph_kerning_for_direction (c->font,
 					     c->buffer->info[i - 1].codepoint, c->buffer->info[i].codepoint,
 					     c->buffer->props.direction,
 					     &x_kern, &y_kern);

     kern1 = x_kern >> 1;
     kern2 = x_kern - kern1;
     c->buffer->pos[i - 1].x_advance += kern1;
     c->buffer->pos[i].x_advance += kern2;
     c->buffer->pos[i].x_offset += kern2;

     kern1 = y_kern >> 1;
     kern2 = y_kern - kern1;
     c->buffer->pos[i - 1].y_advance += kern1;
     c->buffer->pos[i].y_advance += kern2;
     c->buffer->pos[i].y_offset += kern2;
   }
 }

 static void
 hb_position_complex_fallback_visual (hb_ot_shape_context_t *c)
 {
   hb_truetype_kern (c);
 }


 /* Do it! */

 static void
 hb_ot_shape_execute_internal (hb_ot_shape_context_t *c)
 {
   /* Save the original direction, we use it later. */
   c->target_direction = c->buffer->props.direction;

   hb_reset_glyph_infos (c); /* BUFFER: Clear buffer var1 and var2 */

   hb_set_unicode_props (c); /* BUFFER: Set general_category and combining_class in var1 */

   hb_ensure_native_direction (c);

   hb_form_clusters (c);

   hb_ot_shape_setup_masks (c); /* BUFFER: Clobbers var2 */

   /* SUBSTITUTE */
   {
     /* Mirroring needs to see the original direction */
     hb_mirror_chars (c);

     hb_substitute_default (c);

     hb_ot_substitute_complex (c);

     if (!c->applied_substitute_complex)
       hb_substitute_complex_fallback (c);
   }

   /* POSITION */
   {
     hb_position_default (c);

     hb_ot_position_complex (c);

     hb_bool_t position_fallback = !c->applied_position_complex;
     if (position_fallback)
       hb_position_complex_fallback (c);

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

     if (position_fallback)
       hb_position_complex_fallback_visual (c);
   }

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

 static void
 hb_ot_shape_plan_internal (hb_ot_shape_plan_t       *plan,
 			   hb_face_t                *face,
 			   const hb_segment_properties_t  *props,
 			   const hb_feature_t       *user_features,
 			   unsigned int              num_user_features)
 {
   plan->shaper = hb_ot_shape_complex_categorize (props);

   hb_ot_shape_collect_features (plan, props, user_features, num_user_features);

   plan->map.compile (face, props);
 }

 static void
 hb_ot_shape_execute (hb_ot_shape_plan_t *plan,
 		     hb_font_t          *font,
 		     hb_buffer_t        *buffer,
 		     const hb_feature_t *user_features,
 		     unsigned int        num_user_features)
 {
   hb_ot_shape_context_t c = {plan, font, font->face, buffer, user_features, num_user_features};
   hb_ot_shape_execute_internal (&c);
 }

 void
 hb_ot_shape (hb_font_t          *font,
 	     hb_buffer_t        *buffer,
 	     const hb_feature_t *features,
 	     unsigned int        num_features)
 {
   hb_ot_shape_plan_t plan;

   hb_ot_shape_plan_internal (&plan, font->face, &buffer->props, features, num_features);
   hb_ot_shape_execute (&plan, font, buffer, features, num_features);
 }


 HB_END_DECLS
	/*
	* Copyright © 2009,2010 Red Hat, Inc.
	* Copyright © 2010 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
	*/

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

	#include "hb-font-private.hh"

	HB_BEGIN_DECLS


	/* XXX vertical */
	hb_tag_t default_features[] = {
	HB_TAG('c','a','l','t'),
	HB_TAG('c','c','m','p'),
	HB_TAG('c','l','i','g'),
	HB_TAG('c','u','r','s'),
	HB_TAG('k','e','r','n'),
	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 void
	hb_ot_shape_collect_features (hb_ot_shape_plan_t *plan,
	const hb_segment_properties_t *props,
	const hb_feature_t *user_features,
	unsigned int num_user_features)
	{
	switch (props->direction) {
	case HB_DIRECTION_LTR:
	plan->map.add_bool_feature (HB_TAG ('l','t','r','a'));
	plan->map.add_bool_feature (HB_TAG ('l','t','r','m'));
	break;
	case HB_DIRECTION_RTL:
	plan->map.add_bool_feature (HB_TAG ('r','t','l','a'));
	plan->map.add_bool_feature (HB_TAG ('r','t','l','m'), false);
	break;
	case HB_DIRECTION_TTB:
	case HB_DIRECTION_BTT:
	case HB_DIRECTION_INVALID:
	default:
	break;
	}

	for (unsigned int i = 0; i < ARRAY_LENGTH (default_features); i++)
	plan->map.add_bool_feature (default_features[i]);

	hb_ot_shape_complex_collect_features (plan, props);

	for (unsigned int i = 0; i < num_user_features; i++) {
	const hb_feature_t *feature = &user_features[i];
	plan->map.add_feature (feature->tag, feature->value, (feature->start == 0 && feature->end == (unsigned int) -1));
	}
	}


	static void
	hb_ot_shape_setup_masks (hb_ot_shape_context_t *c)
	{
	hb_mask_t global_mask = c->plan->map.get_global_mask ();
	c->buffer->reset_masks (global_mask);

	hb_ot_shape_complex_setup_masks (c); /* BUFFER: Clobbers var2 */

	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 = c->plan->map.get_mask (feature->tag, &shift);
	c->buffer->set_masks (feature->value << shift, mask, feature->start, feature->end);
	}
	}
	}


	static void
	hb_ot_substitute_complex (hb_ot_shape_context_t *c)
	{
	if (!hb_ot_layout_has_substitution (c->face))
	return;

	c->plan->map.substitute (c->face, c->buffer);

	c->applied_substitute_complex = TRUE;
	return;
	}

	static void
	hb_ot_position_complex (hb_ot_shape_context_t *c)
	{

	if (!hb_ot_layout_has_positioning (c->face))
	return;

	unsigned int count = c->buffer->len;
	for (unsigned int i = 0; i < count; i++) {
	hb_font_add_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
	HB_DIRECTION_LTR,
	&c->buffer->pos[i].x_offset,
	&c->buffer->pos[i].y_offset);
	}

	c->plan->map.position (c->font, c->face, c->buffer);

	for (unsigned int i = 0; i < count; i++) {
	hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
	HB_DIRECTION_LTR,
	&c->buffer->pos[i].x_offset,
	&c->buffer->pos[i].y_offset);
	}

	hb_ot_layout_position_finish (c->buffer);

	c->applied_position_complex = TRUE;
	return;
	}


	/* Main shaper */

	/* Prepare */

	static inline hb_bool_t
	is_variation_selector (hb_codepoint_t unicode)
	{
	return unlikely ((unicode >= 0x180B && unicode <= 0x180D) \|\| /* MONGOLIAN FREE VARIATION SELECTOR ONE..THREE */
	(unicode >= 0xFE00 && unicode <= 0xFE0F) \|\| /* VARIATION SELECTOR-1..16 */
	(unicode >= 0xE0100 && unicode <= 0xE01EF)); /* VARIATION SELECTOR-17..256 */
	}

	static void
	hb_set_unicode_props (hb_ot_shape_context_t *c)
	{
	hb_unicode_funcs_t *unicode = c->buffer->unicode;
	hb_glyph_info_t *info = c->buffer->info;

	unsigned int count = c->buffer->len;
	for (unsigned int i = 1; i < count; i++) {
	info[i].general_category() = unicode->get_general_category (info[i].codepoint);
	info[i].combining_class() = unicode->get_combining_class (info[i].codepoint);
	}
	}

	static void
	hb_form_clusters (hb_ot_shape_context_t *c)
	{
	unsigned int count = c->buffer->len;
	for (unsigned int i = 1; i < count; i++)
	if (c->buffer->info[i].general_category() == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)
	c->buffer->info[i].cluster = c->buffer->info[i - 1].cluster;
	}

	static void
	hb_ensure_native_direction (hb_ot_shape_context_t *c)
	{
	hb_direction_t direction = c->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 (c->buffer->props.script)) \|\|
	(HB_DIRECTION_IS_VERTICAL (direction) && direction != HB_DIRECTION_TTB))
	{
	hb_buffer_reverse_clusters (c->buffer);
	c->buffer->props.direction = HB_DIRECTION_REVERSE (c->buffer->props.direction);
	}
	}

	static void
	hb_reset_glyph_infos (hb_ot_shape_context_t *c)
	{
	unsigned int count = c->buffer->len;
	for (unsigned int i = 0; i < count; i++)
	c->buffer->info[i].var1.u32 = c->buffer->info[i].var2.u32 = 0;
	}


	/* Substitute */

	static void
	hb_mirror_chars (hb_ot_shape_context_t *c)
	{
	hb_unicode_funcs_t *unicode = c->buffer->unicode;

	if (HB_DIRECTION_IS_FORWARD (c->target_direction))
	return;

	hb_mask_t rtlm_mask = c->plan->map.get_1_mask (HB_TAG ('r','t','l','m'));

	unsigned int count = c->buffer->len;
	for (unsigned int i = 0; i < count; i++) {
	hb_codepoint_t codepoint = unicode->get_mirroring (c->buffer->info[i].codepoint);
	if (likely (codepoint == c->buffer->info[i].codepoint))
	c->buffer->info[i].mask \|= rtlm_mask; /* XXX this should be moved to before setting user-feature masks */
	else
	c->buffer->info[i].codepoint = codepoint;
	}
	}

	static void
	hb_map_glyphs (hb_font_t *font,
	hb_buffer_t *buffer)
	{
	if (unlikely (!buffer->len))
	return;

	hb_codepoint_t glyph;
	buffer->clear_output ();
	unsigned int count = buffer->len - 1;
	for (buffer->i = 0; buffer->i < count;) {
	if (unlikely (is_variation_selector (buffer->info[buffer->i + 1].codepoint))) {
	hb_font_get_glyph (font, buffer->info[buffer->i].codepoint, buffer->info[buffer->i + 1].codepoint, &glyph);
	buffer->replace_glyph (glyph);
	buffer->i++;
	} else {
	hb_font_get_glyph (font, buffer->info[buffer->i].codepoint, 0, &glyph);
	buffer->replace_glyph (glyph);
	}
	}
	if (likely (buffer->i < buffer->len)) {
	hb_font_get_glyph (font, buffer->info[buffer->i].codepoint, 0, &glyph);
	buffer->replace_glyph (glyph);
	}
	buffer->swap ();
	}

	static void
	hb_substitute_default (hb_ot_shape_context_t *c)
	{
	hb_map_glyphs (c->font, c->buffer);
	}

	static void
	hb_substitute_complex_fallback (hb_ot_shape_context_t *c HB_UNUSED)
	{
	/* TODO Arabic */
	}


	/* Position */

	static void
	hb_position_default (hb_ot_shape_context_t *c)
	{
	hb_ot_layout_position_start (c->buffer);

	unsigned int count = c->buffer->len;
	for (unsigned int i = 0; i < count; i++) {
	hb_font_get_glyph_advance_for_direction (c->font, c->buffer->info[i].codepoint,
	c->buffer->props.direction,
	&c->buffer->pos[i].x_advance,
	&c->buffer->pos[i].y_advance);
	hb_font_subtract_glyph_origin_for_direction (c->font, c->buffer->info[i].codepoint,
	c->buffer->props.direction,
	&c->buffer->pos[i].x_offset,
	&c->buffer->pos[i].y_offset);
	}
	}

	static void
	hb_position_complex_fallback (hb_ot_shape_context_t *c HB_UNUSED)
	{
	/* TODO Mark pos */
	}

	static void
	hb_truetype_kern (hb_ot_shape_context_t *c)
	{
	/* TODO Check for kern=0 */
	unsigned int count = c->buffer->len;
	for (unsigned int i = 1; i < count; i++) {
	hb_position_t x_kern, y_kern, kern1, kern2;
	hb_font_get_glyph_kerning_for_direction (c->font,
	c->buffer->info[i - 1].codepoint, c->buffer->info[i].codepoint,
	c->buffer->props.direction,
	&x_kern, &y_kern);

	kern1 = x_kern >> 1;
	kern2 = x_kern - kern1;
	c->buffer->pos[i - 1].x_advance += kern1;
	c->buffer->pos[i].x_advance += kern2;
	c->buffer->pos[i].x_offset += kern2;

	kern1 = y_kern >> 1;
	kern2 = y_kern - kern1;
	c->buffer->pos[i - 1].y_advance += kern1;
	c->buffer->pos[i].y_advance += kern2;
	c->buffer->pos[i].y_offset += kern2;
	}
	}

	static void
	hb_position_complex_fallback_visual (hb_ot_shape_context_t *c)
	{
	hb_truetype_kern (c);
	}


	/* Do it! */

	static void
	hb_ot_shape_execute_internal (hb_ot_shape_context_t *c)
	{
	/* Save the original direction, we use it later. */
	c->target_direction = c->buffer->props.direction;

	hb_reset_glyph_infos (c); /* BUFFER: Clear buffer var1 and var2 */

	hb_set_unicode_props (c); /* BUFFER: Set general_category and combining_class in var1 */

	hb_ensure_native_direction (c);

	hb_form_clusters (c);

	hb_ot_shape_setup_masks (c); /* BUFFER: Clobbers var2 */

	/* SUBSTITUTE */
	{
	/* Mirroring needs to see the original direction */
	hb_mirror_chars (c);

	hb_substitute_default (c);

	hb_ot_substitute_complex (c);

	if (!c->applied_substitute_complex)
	hb_substitute_complex_fallback (c);
	}

	/* POSITION */
	{
	hb_position_default (c);

	hb_ot_position_complex (c);

	hb_bool_t position_fallback = !c->applied_position_complex;
	if (position_fallback)
	hb_position_complex_fallback (c);

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

	if (position_fallback)
	hb_position_complex_fallback_visual (c);
	}

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

	static void
	hb_ot_shape_plan_internal (hb_ot_shape_plan_t *plan,
	hb_face_t *face,
	const hb_segment_properties_t *props,
	const hb_feature_t *user_features,
	unsigned int num_user_features)
	{
	plan->shaper = hb_ot_shape_complex_categorize (props);

	hb_ot_shape_collect_features (plan, props, user_features, num_user_features);

	plan->map.compile (face, props);
	}

	static void
	hb_ot_shape_execute (hb_ot_shape_plan_t *plan,
	hb_font_t *font,
	hb_buffer_t *buffer,
	const hb_feature_t *user_features,
	unsigned int num_user_features)
	{
	hb_ot_shape_context_t c = {plan, font, font->face, buffer, user_features, num_user_features};
	hb_ot_shape_execute_internal (&c);
	}

	void
	hb_ot_shape (hb_font_t *font,
	hb_buffer_t *buffer,
	const hb_feature_t *features,
	unsigned int num_features)
	{
	hb_ot_shape_plan_t plan;

	hb_ot_shape_plan_internal (&plan, font->face, &buffer->props, features, num_features);
	hb_ot_shape_execute (&plan, font, buffer, features, num_features);
	}


	HB_END_DECLS