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

 /*
  * Copyright © 2011,2012  Google, Inc.
  *
  *  This is part of HarfBuzz, a text shaping library.
  *
  * Permission is hereby granted, without written agreement and without
  * license or royalty fees, to use, copy, modify, and distribute this
  * software and its documentation for any purpose, provided that the
  * above copyright notice and the following two paragraphs appear in
  * all copies of this software.
  *
  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  * DAMAGE.
  *
  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  *
  * Google Author(s): Behdad Esfahbod
  */

 #include "hb-ot-shape-complex-khmer.hh"
 #include "hb-ot-layout.hh"


 /*
  * Khmer shaper.
  */

 static const hb_ot_map_feature_t
 khmer_features[] =
 {
   /*
    * Basic features.
    * These features are applied in order, one at a time, after reordering.
    */
   {HB_TAG('p','r','e','f'), F_MANUAL_JOINERS},
   {HB_TAG('b','l','w','f'), F_MANUAL_JOINERS},
   {HB_TAG('a','b','v','f'), F_MANUAL_JOINERS},
   {HB_TAG('p','s','t','f'), F_MANUAL_JOINERS},
   {HB_TAG('c','f','a','r'), F_MANUAL_JOINERS},
   /*
    * Other features.
    * These features are applied all at once.
    */
   {HB_TAG('p','r','e','s'), F_GLOBAL_MANUAL_JOINERS},
   {HB_TAG('a','b','v','s'), F_GLOBAL_MANUAL_JOINERS},
   {HB_TAG('b','l','w','s'), F_GLOBAL_MANUAL_JOINERS},
   {HB_TAG('p','s','t','s'), F_GLOBAL_MANUAL_JOINERS},
   /*
    * Positioning features.
    * We don't care about the types.
    */
   {HB_TAG('d','i','s','t'), F_GLOBAL},
   {HB_TAG('a','b','v','m'), F_GLOBAL},
   {HB_TAG('b','l','w','m'), F_GLOBAL},
 };

 /*
  * Must be in the same order as the khmer_features array.
  */
 enum {
   PREF,
   BLWF,
   ABVF,
   PSTF,
   CFAR,

   _PRES,
   _ABVS,
   _BLWS,
   _PSTS,

   _DIST,
   _ABVM,
   _BLWM,

   KHMER_NUM_FEATURES,
   KHMER_BASIC_FEATURES = _PRES, /* Don't forget to update this! */
 };

 static void
 setup_syllables (const hb_ot_shape_plan_t *plan,
 		 hb_font_t *font,
 		 hb_buffer_t *buffer);
 static void
 reorder (const hb_ot_shape_plan_t *plan,
 	 hb_font_t *font,
 	 hb_buffer_t *buffer);
 static void
 clear_syllables (const hb_ot_shape_plan_t *plan,
 		 hb_font_t *font,
 		 hb_buffer_t *buffer);

 static void
 collect_features_khmer (hb_ot_shape_planner_t *plan)
 {
   hb_ot_map_builder_t *map = &plan->map;

   /* Do this before any lookups have been applied. */
   map->add_gsub_pause (setup_syllables);
   map->add_gsub_pause (reorder);

   /* Testing suggests that Uniscribe does NOT pause between basic
    * features.  Test with KhmerUI.ttf and the following three
    * sequences:
    *
    *   U+1789,U+17BC
    *   U+1789,U+17D2,U+1789
    *   U+1789,U+17D2,U+1789,U+17BC
    *
    * https://github.com/harfbuzz/harfbuzz/issues/974
    */
   map->enable_feature (HB_TAG('l','o','c','l'));
   map->enable_feature (HB_TAG('c','c','m','p'));

   unsigned int i = 0;
   for (; i < KHMER_BASIC_FEATURES; i++)
     map->add_feature (khmer_features[i]);

   map->add_gsub_pause (clear_syllables);

   for (; i < KHMER_NUM_FEATURES; i++)
     map->add_feature (khmer_features[i]);

   map->enable_feature (HB_TAG('c','a','l','t'));
   map->enable_feature (HB_TAG('c','l','i','g'));

 }

 static void
 override_features_khmer (hb_ot_shape_planner_t *plan)
 {
   /* Uniscribe does not apply 'kern' in Khmer. */
   if (hb_options ().uniscribe_bug_compatible)
   {
     plan->map.disable_feature (HB_TAG('k','e','r','n'));
   }

   plan->map.disable_feature (HB_TAG('l','i','g','a'));
 }


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

   inline bool would_substitute (const hb_codepoint_t *glyphs,
 				unsigned int          glyphs_count,
 				hb_face_t            *face) const
   {
     for (unsigned int i = 0; i < count; i++)
       if (hb_ot_layout_lookup_would_substitute_fast (face, lookups[i].index, glyphs, glyphs_count, zero_context))
 	return true;
     return false;
   }

   private:
   const hb_ot_map_t::lookup_map_t *lookups;
   unsigned int count;
   bool zero_context;
 };

 struct khmer_shape_plan_t
 {
   ASSERT_POD ();

   inline bool get_virama_glyph (hb_font_t *font, hb_codepoint_t *pglyph) const
   {
     hb_codepoint_t glyph = virama_glyph;
     if (unlikely (virama_glyph == (hb_codepoint_t) -1))
     {
       if (!font->get_nominal_glyph (0x17D2u, &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.  It's safe.  Don't worry! */
       virama_glyph = glyph;
     }

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

   mutable hb_codepoint_t virama_glyph;

   would_substitute_feature_t pref;

   hb_mask_t mask_array[KHMER_NUM_FEATURES];
 };

 static void *
 data_create_khmer (const hb_ot_shape_plan_t *plan)
 {
   khmer_shape_plan_t *khmer_plan = (khmer_shape_plan_t *) calloc (1, sizeof (khmer_shape_plan_t));
   if (unlikely (!khmer_plan))
     return nullptr;

   khmer_plan->virama_glyph = (hb_codepoint_t) -1;

   khmer_plan->pref.init (&plan->map, HB_TAG('p','r','e','f'), true);

   for (unsigned int i = 0; i < ARRAY_LENGTH (khmer_plan->mask_array); i++)
     khmer_plan->mask_array[i] = (khmer_features[i].flags & F_GLOBAL) ?
 				 0 : plan->map.get_1_mask (khmer_features[i].tag);

   return khmer_plan;
 }

 static void
 data_destroy_khmer (void *data)
 {
   free (data);
 }


 enum syllable_type_t {
   consonant_syllable,
   broken_cluster,
   non_khmer_cluster,
 };

 #include "hb-ot-shape-complex-khmer-machine.hh"

 static void
 setup_masks_khmer (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		   hb_buffer_t              *buffer,
 		   hb_font_t                *font HB_UNUSED)
 {
   HB_BUFFER_ALLOCATE_VAR (buffer, khmer_category);

   /* 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_khmer_properties (info[i]);
 }

 static void
 setup_syllables (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		 hb_font_t *font HB_UNUSED,
 		 hb_buffer_t *buffer)
 {
   find_syllables (buffer);
   foreach_syllable (buffer, start, end)
     buffer->unsafe_to_break (start, end);
 }


 /* Rules from:
  * https://docs.microsoft.com/en-us/typography/script-development/devanagari */

 static void
 reorder_consonant_syllable (const hb_ot_shape_plan_t *plan,
 			    hb_face_t *face,
 			    hb_buffer_t *buffer,
 			    unsigned int start, unsigned int end)
 {
   const khmer_shape_plan_t *khmer_plan = (const khmer_shape_plan_t *) plan->data;
   hb_glyph_info_t *info = buffer->info;

   /* Setup masks. */
   {
     /* Post-base */
     hb_mask_t mask = khmer_plan->mask_array[BLWF] | khmer_plan->mask_array[ABVF] | khmer_plan->mask_array[PSTF];
     for (unsigned int i = start + 1; i < end; i++)
       info[i].mask  |= mask;
   }

   unsigned int num_coengs = 0;
   for (unsigned int i = start + 1; i < end; i++)
   {
     /* """
      * When a COENG + (Cons | IndV) combination are found (and subscript count
      * is less than two) the character combination is handled according to the
      * subscript type of the character following the COENG.
      *
      * ...
      *
      * Subscript Type 2 - The COENG + RO characters are reordered to immediately
      * before the base glyph. Then the COENG + RO characters are assigned to have
      * the 'pref' OpenType feature applied to them.
      * """
      */
     if (info[i].khmer_category() == OT_Coeng && num_coengs <= 2 && i + 1 < end)
     {
       num_coengs++;

       if (info[i + 1].khmer_category() == OT_Ra)
       {
 	for (unsigned int j = 0; j < 2; j++)
 	  info[i + j].mask |= khmer_plan->mask_array[PREF];

 	/* Move the Coeng,Ro sequence to the start. */
 	buffer->merge_clusters (start, i + 2);
 	hb_glyph_info_t t0 = info[i];
 	hb_glyph_info_t t1 = info[i + 1];
 	memmove (&info[start + 2], &info[start], (i - start) * sizeof (info[0]));
 	info[start] = t0;
 	info[start + 1] = t1;

 	/* Mark the subsequent stuff with 'cfar'.  Used in Khmer.
 	 * Read the feature spec.
 	 * This allows distinguishing the following cases with MS Khmer fonts:
 	 * U+1784,U+17D2,U+179A,U+17D2,U+1782
 	 * U+1784,U+17D2,U+1782,U+17D2,U+179A
 	 */
 	if (khmer_plan->mask_array[CFAR])
 	  for (unsigned int j = i + 2; j < end; j++)
 	    info[j].mask |= khmer_plan->mask_array[CFAR];

 	num_coengs = 2; /* Done. */
       }
     }

     /* Reorder left matra piece. */
     else if (info[i].khmer_category() == OT_VPre)
     {
       /* Move to the start. */
       buffer->merge_clusters (start, i + 1);
       hb_glyph_info_t t = info[i];
       memmove (&info[start + 1], &info[start], (i - start) * sizeof (info[0]));
       info[start] = t;
     }
   }
 }

 static void
 initial_reordering_syllable (const hb_ot_shape_plan_t *plan,
 			     hb_face_t *face,
 			     hb_buffer_t *buffer,
 			     unsigned int start, unsigned int end)
 {
   syllable_type_t syllable_type = (syllable_type_t) (buffer->info[start].syllable() & 0x0F);
   switch (syllable_type)
   {
     case broken_cluster: /* We already inserted dotted-circles, so just call the consonant_syllable. */
     case consonant_syllable:
      reorder_consonant_syllable (plan, face, buffer, start, end);
      break;

     case non_khmer_cluster:
       break;
   }
 }

 static inline void
 insert_dotted_circles (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		       hb_font_t *font,
 		       hb_buffer_t *buffer)
 {
   /* Note: This loop is extra overhead, but should not be measurable. */
   bool has_broken_syllables = false;
   unsigned int count = buffer->len;
   hb_glyph_info_t *info = buffer->info;
   for (unsigned int i = 0; i < count; i++)
     if ((info[i].syllable() & 0x0F) == broken_cluster)
     {
       has_broken_syllables = true;
       break;
     }
   if (likely (!has_broken_syllables))
     return;


   hb_codepoint_t dottedcircle_glyph;
   if (!font->get_nominal_glyph (0x25CCu, &dottedcircle_glyph))
     return;

   hb_glyph_info_t dottedcircle = {0};
   dottedcircle.codepoint = 0x25CCu;
   set_khmer_properties (dottedcircle);
   dottedcircle.codepoint = dottedcircle_glyph;

   buffer->clear_output ();

   buffer->idx = 0;
   unsigned int last_syllable = 0;
   while (buffer->idx < buffer->len && buffer->successful)
   {
     unsigned int syllable = buffer->cur().syllable();
     syllable_type_t syllable_type = (syllable_type_t) (syllable & 0x0F);
     if (unlikely (last_syllable != syllable && syllable_type == broken_cluster))
     {
       last_syllable = syllable;

       hb_glyph_info_t ginfo = dottedcircle;
       ginfo.cluster = buffer->cur().cluster;
       ginfo.mask = buffer->cur().mask;
       ginfo.syllable() = buffer->cur().syllable();
       /* TODO Set glyph_props? */

       /* Insert dottedcircle after possible Repha. */
       while (buffer->idx < buffer->len && buffer->successful &&
 	     last_syllable == buffer->cur().syllable() &&
 	     buffer->cur().khmer_category() == OT_Repha)
         buffer->next_glyph ();

       buffer->output_info (ginfo);
     }
     else
       buffer->next_glyph ();
   }

   buffer->swap_buffers ();
 }

 static void
 reorder (const hb_ot_shape_plan_t *plan,
 	 hb_font_t *font,
 	 hb_buffer_t *buffer)
 {
   insert_dotted_circles (plan, font, buffer);

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

   HB_BUFFER_DEALLOCATE_VAR (buffer, khmer_category);
 }

 static void
 clear_syllables (const hb_ot_shape_plan_t *plan HB_UNUSED,
 		 hb_font_t *font HB_UNUSED,
 		 hb_buffer_t *buffer)
 {
   /* TODO: In USE, we clear syllables right after reorder.  Figure out
    * what Uniscribe does. */
   hb_glyph_info_t *info = buffer->info;
   unsigned int count = buffer->len;
   for (unsigned int i = 0; i < count; i++)
     info[i].syllable() = 0;
 }


 static bool
 decompose_khmer (const hb_ot_shape_normalize_context_t *c,
 		 hb_codepoint_t  ab,
 		 hb_codepoint_t *a,
 		 hb_codepoint_t *b)
 {
   switch (ab)
   {
     /*
      * Decompose split matras that don't have Unicode decompositions.
      */

     /* Khmer */
     case 0x17BEu  : *a = 0x17C1u; *b= 0x17BEu; return true;
     case 0x17BFu  : *a = 0x17C1u; *b= 0x17BFu; return true;
     case 0x17C0u  : *a = 0x17C1u; *b= 0x17C0u; return true;
     case 0x17C4u  : *a = 0x17C1u; *b= 0x17C4u; return true;
     case 0x17C5u  : *a = 0x17C1u; *b= 0x17C5u; return true;
   }

   return (bool) c->unicode->decompose (ab, a, b);
 }

 static bool
 compose_khmer (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;

   return (bool) c->unicode->compose (a, b, ab);
 }


 const hb_ot_complex_shaper_t _hb_ot_complex_shaper_khmer =
 {
   collect_features_khmer,
   override_features_khmer,
   data_create_khmer,
   data_destroy_khmer,
   nullptr, /* preprocess_text */
   nullptr, /* postprocess_glyphs */
   HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT,
   decompose_khmer,
   compose_khmer,
   setup_masks_khmer,
   HB_TAG_NONE, /* gpos_tag */
   nullptr, /* reorder_marks */
   HB_OT_SHAPE_ZERO_WIDTH_MARKS_NONE,
   false, /* fallback_position */
 };
	/*
	* Copyright © 2011,2012 Google, Inc.
	*
	* This is part of HarfBuzz, a text shaping library.
	*
	* Permission is hereby granted, without written agreement and without
	* license or royalty fees, to use, copy, modify, and distribute this
	* software and its documentation for any purpose, provided that the
	* above copyright notice and the following two paragraphs appear in
	* all copies of this software.
	*
	* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
	* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
	* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
	* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
	* DAMAGE.
	*
	* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
	* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
	* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
	* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
	* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
	*
	* Google Author(s): Behdad Esfahbod
	*/

	#include "hb-ot-shape-complex-khmer.hh"
	#include "hb-ot-layout.hh"


	/*
	* Khmer shaper.
	*/

	static const hb_ot_map_feature_t
	khmer_features[] =
	{
	/*
	* Basic features.
	* These features are applied in order, one at a time, after reordering.
	*/
	{HB_TAG('p','r','e','f'), F_MANUAL_JOINERS},
	{HB_TAG('b','l','w','f'), F_MANUAL_JOINERS},
	{HB_TAG('a','b','v','f'), F_MANUAL_JOINERS},
	{HB_TAG('p','s','t','f'), F_MANUAL_JOINERS},
	{HB_TAG('c','f','a','r'), F_MANUAL_JOINERS},
	/*
	* Other features.
	* These features are applied all at once.
	*/
	{HB_TAG('p','r','e','s'), F_GLOBAL_MANUAL_JOINERS},
	{HB_TAG('a','b','v','s'), F_GLOBAL_MANUAL_JOINERS},
	{HB_TAG('b','l','w','s'), F_GLOBAL_MANUAL_JOINERS},
	{HB_TAG('p','s','t','s'), F_GLOBAL_MANUAL_JOINERS},
	/*
	* Positioning features.
	* We don't care about the types.
	*/
	{HB_TAG('d','i','s','t'), F_GLOBAL},
	{HB_TAG('a','b','v','m'), F_GLOBAL},
	{HB_TAG('b','l','w','m'), F_GLOBAL},
	};

	/*
	* Must be in the same order as the khmer_features array.
	*/
	enum {
	PREF,
	BLWF,
	ABVF,
	PSTF,
	CFAR,

	_PRES,
	_ABVS,
	_BLWS,
	_PSTS,

	_DIST,
	_ABVM,
	_BLWM,

	KHMER_NUM_FEATURES,
	KHMER_BASIC_FEATURES = _PRES, /* Don't forget to update this! */
	};

	static void
	setup_syllables (const hb_ot_shape_plan_t *plan,
	hb_font_t *font,
	hb_buffer_t *buffer);
	static void
	reorder (const hb_ot_shape_plan_t *plan,
	hb_font_t *font,
	hb_buffer_t *buffer);
	static void
	clear_syllables (const hb_ot_shape_plan_t *plan,
	hb_font_t *font,
	hb_buffer_t *buffer);

	static void
	collect_features_khmer (hb_ot_shape_planner_t *plan)
	{
	hb_ot_map_builder_t *map = &plan->map;

	/* Do this before any lookups have been applied. */
	map->add_gsub_pause (setup_syllables);
	map->add_gsub_pause (reorder);

	/* Testing suggests that Uniscribe does NOT pause between basic
	* features. Test with KhmerUI.ttf and the following three
	* sequences:
	*
	* U+1789,U+17BC
	* U+1789,U+17D2,U+1789
	* U+1789,U+17D2,U+1789,U+17BC
	*
	* https://github.com/harfbuzz/harfbuzz/issues/974
	*/
	map->enable_feature (HB_TAG('l','o','c','l'));
	map->enable_feature (HB_TAG('c','c','m','p'));

	unsigned int i = 0;
	for (; i < KHMER_BASIC_FEATURES; i++)
	map->add_feature (khmer_features[i]);

	map->add_gsub_pause (clear_syllables);

	for (; i < KHMER_NUM_FEATURES; i++)
	map->add_feature (khmer_features[i]);

	map->enable_feature (HB_TAG('c','a','l','t'));
	map->enable_feature (HB_TAG('c','l','i','g'));

	}

	static void
	override_features_khmer (hb_ot_shape_planner_t *plan)
	{
	/* Uniscribe does not apply 'kern' in Khmer. */
	if (hb_options ().uniscribe_bug_compatible)
	{
	plan->map.disable_feature (HB_TAG('k','e','r','n'));
	}

	plan->map.disable_feature (HB_TAG('l','i','g','a'));
	}


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

	inline bool would_substitute (const hb_codepoint_t *glyphs,
	unsigned int glyphs_count,
	hb_face_t *face) const
	{
	for (unsigned int i = 0; i < count; i++)
	if (hb_ot_layout_lookup_would_substitute_fast (face, lookups[i].index, glyphs, glyphs_count, zero_context))
	return true;
	return false;
	}

	private:
	const hb_ot_map_t::lookup_map_t *lookups;
	unsigned int count;
	bool zero_context;
	};

	struct khmer_shape_plan_t
	{
	ASSERT_POD ();

	inline bool get_virama_glyph (hb_font_t font, hb_codepoint_t pglyph) const
	{
	hb_codepoint_t glyph = virama_glyph;
	if (unlikely (virama_glyph == (hb_codepoint_t) -1))
	{
	if (!font->get_nominal_glyph (0x17D2u, &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. It's safe. Don't worry! */
	virama_glyph = glyph;
	}

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

	mutable hb_codepoint_t virama_glyph;

	would_substitute_feature_t pref;

	hb_mask_t mask_array[KHMER_NUM_FEATURES];
	};

	static void *
	data_create_khmer (const hb_ot_shape_plan_t *plan)
	{
	khmer_shape_plan_t khmer_plan = (khmer_shape_plan_t ) calloc (1, sizeof (khmer_shape_plan_t));
	if (unlikely (!khmer_plan))
	return nullptr;

	khmer_plan->virama_glyph = (hb_codepoint_t) -1;

	khmer_plan->pref.init (&plan->map, HB_TAG('p','r','e','f'), true);

	for (unsigned int i = 0; i < ARRAY_LENGTH (khmer_plan->mask_array); i++)
	khmer_plan->mask_array[i] = (khmer_features[i].flags & F_GLOBAL) ?
	0 : plan->map.get_1_mask (khmer_features[i].tag);

	return khmer_plan;
	}

	static void
	data_destroy_khmer (void *data)
	{
	free (data);
	}


	enum syllable_type_t {
	consonant_syllable,
	broken_cluster,
	non_khmer_cluster,
	};

	#include "hb-ot-shape-complex-khmer-machine.hh"

	static void
	setup_masks_khmer (const hb_ot_shape_plan_t *plan HB_UNUSED,
	hb_buffer_t *buffer,
	hb_font_t *font HB_UNUSED)
	{
	HB_BUFFER_ALLOCATE_VAR (buffer, khmer_category);

	/* 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_khmer_properties (info[i]);
	}

	static void
	setup_syllables (const hb_ot_shape_plan_t *plan HB_UNUSED,
	hb_font_t *font HB_UNUSED,
	hb_buffer_t *buffer)
	{
	find_syllables (buffer);
	foreach_syllable (buffer, start, end)
	buffer->unsafe_to_break (start, end);
	}


	/* Rules from:
	* https://docs.microsoft.com/en-us/typography/script-development/devanagari */

	static void
	reorder_consonant_syllable (const hb_ot_shape_plan_t *plan,
	hb_face_t *face,
	hb_buffer_t *buffer,
	unsigned int start, unsigned int end)
	{
	const khmer_shape_plan_t khmer_plan = (const khmer_shape_plan_t ) plan->data;
	hb_glyph_info_t *info = buffer->info;

	/* Setup masks. */
	{
	/* Post-base */
	hb_mask_t mask = khmer_plan->mask_array[BLWF] \| khmer_plan->mask_array[ABVF] \| khmer_plan->mask_array[PSTF];
	for (unsigned int i = start + 1; i < end; i++)
	info[i].mask \|= mask;
	}

	unsigned int num_coengs = 0;
	for (unsigned int i = start + 1; i < end; i++)
	{
	/* """
	* When a COENG + (Cons \| IndV) combination are found (and subscript count
	* is less than two) the character combination is handled according to the
	* subscript type of the character following the COENG.
	*
	* ...
	*
	* Subscript Type 2 - The COENG + RO characters are reordered to immediately
	* before the base glyph. Then the COENG + RO characters are assigned to have
	* the 'pref' OpenType feature applied to them.
	* """
	*/
	if (info[i].khmer_category() == OT_Coeng && num_coengs <= 2 && i + 1 < end)
	{
	num_coengs++;

	if (info[i + 1].khmer_category() == OT_Ra)
	{
	for (unsigned int j = 0; j < 2; j++)
	info[i + j].mask \|= khmer_plan->mask_array[PREF];

	/* Move the Coeng,Ro sequence to the start. */
	buffer->merge_clusters (start, i + 2);
	hb_glyph_info_t t0 = info[i];
	hb_glyph_info_t t1 = info[i + 1];
	memmove (&info[start + 2], &info[start], (i - start) * sizeof (info[0]));
	info[start] = t0;
	info[start + 1] = t1;

	/* Mark the subsequent stuff with 'cfar'. Used in Khmer.
	* Read the feature spec.
	* This allows distinguishing the following cases with MS Khmer fonts:
	* U+1784,U+17D2,U+179A,U+17D2,U+1782
	* U+1784,U+17D2,U+1782,U+17D2,U+179A
	*/
	if (khmer_plan->mask_array[CFAR])
	for (unsigned int j = i + 2; j < end; j++)
	info[j].mask \|= khmer_plan->mask_array[CFAR];

	num_coengs = 2; /* Done. */
	}
	}

	/* Reorder left matra piece. */
	else if (info[i].khmer_category() == OT_VPre)
	{
	/* Move to the start. */
	buffer->merge_clusters (start, i + 1);
	hb_glyph_info_t t = info[i];
	memmove (&info[start + 1], &info[start], (i - start) * sizeof (info[0]));
	info[start] = t;
	}
	}
	}

	static void
	initial_reordering_syllable (const hb_ot_shape_plan_t *plan,
	hb_face_t *face,
	hb_buffer_t *buffer,
	unsigned int start, unsigned int end)
	{
	syllable_type_t syllable_type = (syllable_type_t) (buffer->info[start].syllable() & 0x0F);
	switch (syllable_type)
	{
	case broken_cluster: /* We already inserted dotted-circles, so just call the consonant_syllable. */
	case consonant_syllable:
	reorder_consonant_syllable (plan, face, buffer, start, end);
	break;

	case non_khmer_cluster:
	break;
	}
	}

	static inline void
	insert_dotted_circles (const hb_ot_shape_plan_t *plan HB_UNUSED,
	hb_font_t *font,
	hb_buffer_t *buffer)
	{
	/* Note: This loop is extra overhead, but should not be measurable. */
	bool has_broken_syllables = false;
	unsigned int count = buffer->len;
	hb_glyph_info_t *info = buffer->info;
	for (unsigned int i = 0; i < count; i++)
	if ((info[i].syllable() & 0x0F) == broken_cluster)
	{
	has_broken_syllables = true;
	break;
	}
	if (likely (!has_broken_syllables))
	return;


	hb_codepoint_t dottedcircle_glyph;
	if (!font->get_nominal_glyph (0x25CCu, &dottedcircle_glyph))
	return;

	hb_glyph_info_t dottedcircle = {0};
	dottedcircle.codepoint = 0x25CCu;
	set_khmer_properties (dottedcircle);
	dottedcircle.codepoint = dottedcircle_glyph;

	buffer->clear_output ();

	buffer->idx = 0;
	unsigned int last_syllable = 0;
	while (buffer->idx < buffer->len && buffer->successful)
	{
	unsigned int syllable = buffer->cur().syllable();
	syllable_type_t syllable_type = (syllable_type_t) (syllable & 0x0F);
	if (unlikely (last_syllable != syllable && syllable_type == broken_cluster))
	{
	last_syllable = syllable;

	hb_glyph_info_t ginfo = dottedcircle;
	ginfo.cluster = buffer->cur().cluster;
	ginfo.mask = buffer->cur().mask;
	ginfo.syllable() = buffer->cur().syllable();
	/* TODO Set glyph_props? */

	/* Insert dottedcircle after possible Repha. */
	while (buffer->idx < buffer->len && buffer->successful &&
	last_syllable == buffer->cur().syllable() &&
	buffer->cur().khmer_category() == OT_Repha)
	buffer->next_glyph ();

	buffer->output_info (ginfo);
	}
	else
	buffer->next_glyph ();
	}

	buffer->swap_buffers ();
	}

	static void
	reorder (const hb_ot_shape_plan_t *plan,
	hb_font_t *font,
	hb_buffer_t *buffer)
	{
	insert_dotted_circles (plan, font, buffer);

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

	HB_BUFFER_DEALLOCATE_VAR (buffer, khmer_category);
	}

	static void
	clear_syllables (const hb_ot_shape_plan_t *plan HB_UNUSED,
	hb_font_t *font HB_UNUSED,
	hb_buffer_t *buffer)
	{
	/* TODO: In USE, we clear syllables right after reorder. Figure out
	* what Uniscribe does. */
	hb_glyph_info_t *info = buffer->info;
	unsigned int count = buffer->len;
	for (unsigned int i = 0; i < count; i++)
	info[i].syllable() = 0;
	}


	static bool
	decompose_khmer (const hb_ot_shape_normalize_context_t *c,
	hb_codepoint_t ab,
	hb_codepoint_t *a,
	hb_codepoint_t *b)
	{
	switch (ab)
	{
	/*
	* Decompose split matras that don't have Unicode decompositions.
	*/

	/* Khmer */
	case 0x17BEu : a = 0x17C1u; b= 0x17BEu; return true;
	case 0x17BFu : a = 0x17C1u; b= 0x17BFu; return true;
	case 0x17C0u : a = 0x17C1u; b= 0x17C0u; return true;
	case 0x17C4u : a = 0x17C1u; b= 0x17C4u; return true;
	case 0x17C5u : a = 0x17C1u; b= 0x17C5u; return true;
	}

	return (bool) c->unicode->decompose (ab, a, b);
	}

	static bool
	compose_khmer (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;

	return (bool) c->unicode->compose (a, b, ab);
	}


	const hb_ot_complex_shaper_t _hb_ot_complex_shaper_khmer =
	{
	collect_features_khmer,
	override_features_khmer,
	data_create_khmer,
	data_destroy_khmer,
	nullptr, /* preprocess_text */
	nullptr, /* postprocess_glyphs */
	HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT,
	decompose_khmer,
	compose_khmer,
	setup_masks_khmer,
	HB_TAG_NONE, /* gpos_tag */
	nullptr, /* reorder_marks */
	HB_OT_SHAPE_ZERO_WIDTH_MARKS_NONE,
	false, /* fallback_position */
	};