src/hb-ot-hmtx-table.hh - 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, Roderick Sheeter
  */

 #ifndef HB_OT_HMTX_TABLE_HH
 #define HB_OT_HMTX_TABLE_HH

 #include "hb-open-type.hh"
 #include "hb-ot-maxp-table.hh"
 #include "hb-ot-hhea-table.hh"
 #include "hb-ot-var-hvar-table.hh"
 #include "hb-ot-var-mvar-table.hh"
 #include "hb-ot-metrics.hh"

 /*
  * hmtx -- Horizontal Metrics
  * https://docs.microsoft.com/en-us/typography/opentype/spec/hmtx
  * vmtx -- Vertical Metrics
  * https://docs.microsoft.com/en-us/typography/opentype/spec/vmtx
  */
 #define HB_OT_TAG_hmtx HB_TAG('h','m','t','x')
 #define HB_OT_TAG_vmtx HB_TAG('v','m','t','x')


 HB_INTERNAL bool
 _glyf_get_leading_bearing_with_var_unscaled (hb_font_t *font, hb_codepoint_t glyph, bool is_vertical, int *lsb);

 HB_INTERNAL unsigned
 _glyf_get_advance_with_var_unscaled (hb_font_t *font, hb_codepoint_t glyph, bool is_vertical);


 namespace OT {


 struct LongMetric
 {
   UFWORD	advance; /* Advance width/height. */
   FWORD		sb; /* Leading (left/top) side bearing. */
   public:
   DEFINE_SIZE_STATIC (4);
 };


 template <typename T/*Data table type*/, typename H/*Header table type*/, typename V/*Var table type*/>
 struct hmtxvmtx
 {
   bool sanitize (hb_sanitize_context_t *c HB_UNUSED) const
   {
     TRACE_SANITIZE (this);
     /* We don't check for anything specific here.  The users of the
      * struct do all the hard work... */
     return_trace (true);
   }

   const hb_hashmap_t<hb_codepoint_t, hb_pair_t<unsigned, int>>* get_mtx_map (const hb_subset_plan_t *plan) const
   { return T::is_horizontal ? &plan->hmtx_map : &plan->vmtx_map; }

   bool subset_update_header (hb_subset_context_t *c,
 			     unsigned int num_hmetrics,
 			     const hb_hashmap_t<hb_codepoint_t, hb_pair_t<unsigned, int>> *mtx_map,
 			     const hb_map_t *bounds_map) const
   {
     hb_blob_t *src_blob = hb_sanitize_context_t ().reference_table<H> (c->plan->source, H::tableTag);
     hb_blob_t *dest_blob = hb_blob_copy_writable_or_fail (src_blob);
     hb_blob_destroy (src_blob);

     if (unlikely (!dest_blob)) {
       return false;
     }

     unsigned int length;
     H *table = (H *) hb_blob_get_data (dest_blob, &length);
     table->numberOfLongMetrics = num_hmetrics;

 #ifndef HB_NO_VAR
     if (c->plan->normalized_coords)
     {
       auto &MVAR = *c->plan->source->table.MVAR;
       if (T::is_horizontal)
       {
 	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_HORIZONTAL_CARET_RISE,   caretSlopeRise);
 	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_HORIZONTAL_CARET_RUN,    caretSlopeRun);
 	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_HORIZONTAL_CARET_OFFSET, caretOffset);
       }
       else
       {
 	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_VERTICAL_CARET_RISE,     caretSlopeRise);
 	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_VERTICAL_CARET_RUN,      caretSlopeRun);
 	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_VERTICAL_CARET_OFFSET,   caretOffset);
       }

       int min_lsb = 0x7FFF;
       int min_rsb = 0x7FFF;
       int max_extent = -0x7FFF;
       unsigned max_adv = 0;
       for (const auto _ : *mtx_map)
       {
         hb_codepoint_t gid = _.first;
         unsigned adv = _.second.first;
         int lsb = _.second.second;
         max_adv = hb_max (max_adv, adv);

         if (bounds_map->has (gid))
         {
           unsigned bound_width = bounds_map->get (gid);
           int rsb = adv - lsb - bound_width;
           int extent = lsb + bound_width;
           min_lsb = hb_min (min_lsb, lsb);
           min_rsb = hb_min (min_rsb, rsb);
           max_extent = hb_max (max_extent, extent);
         }
       }

       table->advanceMax = max_adv;
       if (!bounds_map->is_empty ())
       {
         table->minLeadingBearing = min_lsb;
         table->minTrailingBearing = min_rsb;
         table->maxExtent = max_extent;
       }
     }
 #endif

     bool result = c->plan->add_table (H::tableTag, dest_blob);
     hb_blob_destroy (dest_blob);

     return result;
   }

   template<typename Iterator,
 	   hb_requires (hb_is_iterator (Iterator))>
   void serialize (hb_serialize_context_t *c,
 		  Iterator it,
 		  unsigned num_long_metrics)
   {
     unsigned idx = 0;
     for (auto _ : it)
     {
       if (idx < num_long_metrics)
       {
 	LongMetric lm;
 	lm.advance = _.first;
 	lm.sb = _.second;
 	if (unlikely (!c->embed<LongMetric> (&lm))) return;
       }
       else
       {
 	FWORD *sb = c->allocate_size<FWORD> (FWORD::static_size);
 	if (unlikely (!sb)) return;
 	*sb = _.second;
       }
       idx++;
     }
   }

   bool subset (hb_subset_context_t *c) const
   {
     TRACE_SUBSET (this);

     T *table_prime = c->serializer->start_embed <T> ();
     if (unlikely (!table_prime)) return_trace (false);

     accelerator_t _mtx (c->plan->source);
     unsigned num_long_metrics;
     const hb_hashmap_t<hb_codepoint_t, hb_pair_t<unsigned, int>> *mtx_map = get_mtx_map (c->plan);
     {
       /* Determine num_long_metrics to encode. */
       auto& plan = c->plan;

       num_long_metrics = plan->num_output_glyphs ();
       unsigned int last_advance = get_new_gid_advance_unscaled (plan, mtx_map, num_long_metrics - 1, _mtx);
       while (num_long_metrics > 1 &&
 	     last_advance == get_new_gid_advance_unscaled (plan, mtx_map, num_long_metrics - 2, _mtx))
       {
 	num_long_metrics--;
       }
     }

     auto it =
     + hb_range (c->plan->num_output_glyphs ())
     | hb_map ([c, &_mtx, mtx_map] (unsigned _)
 	      {
 		if (!mtx_map->has (_))
 		{
 		  hb_codepoint_t old_gid;
 		  if (!c->plan->old_gid_for_new_gid (_, &old_gid))
 		    return hb_pair (0u, 0);
 		  int lsb = 0;
 		  (void) _mtx.get_leading_bearing_without_var_unscaled (old_gid, &lsb);
 		  return hb_pair (_mtx.get_advance_without_var_unscaled (old_gid), +lsb);
 		}
 		return mtx_map->get (_);
 	      })
     ;

     table_prime->serialize (c->serializer, it, num_long_metrics);

     if (unlikely (c->serializer->in_error ()))
       return_trace (false);

     // Amend header num hmetrics
     if (unlikely (!subset_update_header (c, num_long_metrics, mtx_map,
                                          T::is_horizontal ? &c->plan->bounds_width_map : &c->plan->bounds_height_map)))
       return_trace (false);

     return_trace (true);
   }

   struct accelerator_t
   {
     friend struct hmtxvmtx;

     accelerator_t (hb_face_t *face)
     {
       table = hb_sanitize_context_t ().reference_table<hmtxvmtx> (face, T::tableTag);
       var_table = hb_sanitize_context_t ().reference_table<V> (face, T::variationsTag);

       default_advance = T::is_horizontal ? hb_face_get_upem (face) / 2 : hb_face_get_upem (face);

       /* Populate count variables and sort them out as we go */

       unsigned int len = table.get_length ();
       if (len & 1)
         len--;

       num_long_metrics = T::is_horizontal ?
 			 face->table.hhea->numberOfLongMetrics :
 #ifndef HB_NO_VERTICAL
 			 face->table.vhea->numberOfLongMetrics
 #else
 			 0
 #endif
 			 ;
       if (unlikely (num_long_metrics * 4 > len))
 	num_long_metrics = len / 4;
       len -= num_long_metrics * 4;

       num_bearings = face->table.maxp->get_num_glyphs ();

       if (unlikely (num_bearings < num_long_metrics))
         num_bearings = num_long_metrics;
       if (unlikely ((num_bearings - num_long_metrics) * 2 > len))
         num_bearings = num_long_metrics + len / 2;
       len -= (num_bearings - num_long_metrics) * 2;

       /* We MUST set num_bearings to zero if num_long_metrics is zero.
        * Our get_advance() depends on that. */
       if (unlikely (!num_long_metrics))
 	num_bearings = num_long_metrics = 0;

       num_advances = num_bearings + len / 2;
       num_glyphs = face->get_num_glyphs ();
       if (num_glyphs < num_advances)
         num_glyphs = num_advances;
     }
     ~accelerator_t ()
     {
       table.destroy ();
       var_table.destroy ();
     }

     bool has_data () const { return (bool) num_bearings; }

     bool get_leading_bearing_without_var_unscaled (hb_codepoint_t glyph,
 						   int *lsb) const
     {
       if (glyph < num_long_metrics)
       {
 	*lsb = table->longMetricZ[glyph].sb;
 	return true;
       }

       if (unlikely (glyph >= num_bearings))
 	return false;

       const FWORD *bearings = (const FWORD *) &table->longMetricZ[num_long_metrics];
       *lsb = bearings[glyph - num_long_metrics];
       return true;
     }

     bool get_leading_bearing_with_var_unscaled (hb_font_t *font,
 						hb_codepoint_t glyph,
 						int *lsb) const
     {
       if (!font->num_coords)
 	return get_leading_bearing_without_var_unscaled (glyph, lsb);

 #ifndef HB_NO_VAR
       float delta;
       if (var_table->get_lsb_delta_unscaled (glyph, font->coords, font->num_coords, &delta) &&
 	  get_leading_bearing_without_var_unscaled (glyph, lsb))
       {
 	*lsb += roundf (delta);
 	return true;
       }

       return _glyf_get_leading_bearing_with_var_unscaled (font, glyph, T::tableTag == HB_OT_TAG_vmtx, lsb);
 #else
       return false;
 #endif
     }

     unsigned int get_advance_without_var_unscaled (hb_codepoint_t glyph) const
     {
       /* OpenType case. */
       if (glyph < num_bearings)
 	return table->longMetricZ[hb_min (glyph, (uint32_t) num_long_metrics - 1)].advance;

       /* If num_advances is zero, it means we don't have the metrics table
        * for this direction: return default advance.  Otherwise, there's a
        * well-defined answer. */
       if (unlikely (!num_advances))
 	return default_advance;

 #ifdef HB_NO_BEYOND_64K
       return 0;
 #endif

       if (unlikely (glyph >= num_glyphs))
         return 0;

       /* num_bearings <= glyph < num_glyphs;
        * num_bearings <= num_advances */

       if (num_bearings == num_advances)
         return get_advance_without_var_unscaled (num_bearings - 1);

       const FWORD *bearings = (const FWORD *) &table->longMetricZ[num_long_metrics];
       const UFWORD *advances = (const UFWORD *) &bearings[num_bearings - num_long_metrics];

       return advances[hb_min (glyph - num_bearings, num_advances - num_bearings - 1)];
     }

     unsigned get_advance_with_var_unscaled (hb_codepoint_t  glyph,
 					    hb_font_t      *font,
 					    VariationStore::cache_t *store_cache = nullptr) const
     {
       unsigned int advance = get_advance_without_var_unscaled (glyph);

 #ifndef HB_NO_VAR
       if (unlikely (glyph >= num_bearings) || !font->num_coords)
 	return advance;

       if (var_table.get_length ())
 	return advance + roundf (var_table->get_advance_delta_unscaled (glyph,
 									font->coords, font->num_coords,
 									store_cache));

       return _glyf_get_advance_with_var_unscaled (font, glyph, T::tableTag == HB_OT_TAG_vmtx);
 #else
       return advance;
 #endif
     }

     protected:
     // 0 <= num_long_metrics <= num_bearings <= num_advances <= num_glyphs
     unsigned num_long_metrics;
     unsigned num_bearings;
     unsigned num_advances;
     unsigned num_glyphs;

     unsigned int default_advance;

     public:
     hb_blob_ptr_t<hmtxvmtx> table;
     hb_blob_ptr_t<V> var_table;
   };

   /* get advance: when no variations, call get_advance_without_var_unscaled.
    * when there're variations, get advance value from mtx_map in subset_plan*/
   unsigned get_new_gid_advance_unscaled (const hb_subset_plan_t *plan,
                                          const hb_hashmap_t<hb_codepoint_t, hb_pair_t<unsigned, int>> *mtx_map,
                                          unsigned new_gid,
                                          const accelerator_t &_mtx) const
   {
     if (mtx_map->is_empty ())
     {
       hb_codepoint_t old_gid = 0;
       return plan->old_gid_for_new_gid (new_gid, &old_gid) ?
              _mtx.get_advance_without_var_unscaled (old_gid) : 0;
     }
     return mtx_map->get (new_gid).first;
   }

   protected:
   UnsizedArrayOf<LongMetric>
 		longMetricZ;	/* Paired advance width and leading
 				 * bearing values for each glyph. The
 				 * value numOfHMetrics comes from
 				 * the 'hhea' table. If the font is
 				 * monospaced, only one entry need
 				 * be in the array, but that entry is
 				 * required. The last entry applies to
 				 * all subsequent glyphs. */
 /*UnsizedArrayOf<FWORD>	leadingBearingX;*/
 				/* Here the advance is assumed
 				 * to be the same as the advance
 				 * for the last entry above. The
 				 * number of entries in this array is
 				 * derived from numGlyphs (from 'maxp'
 				 * table) minus numberOfLongMetrics.
 				 * This generally is used with a run
 				 * of monospaced glyphs (e.g., Kanji
 				 * fonts or Courier fonts). Only one
 				 * run is allowed and it must be at
 				 * the end. This allows a monospaced
 				 * font to vary the side bearing
 				 * values for each glyph. */
 /*UnsizedArrayOf<UFWORD>advancesX;*/
 				/* TODO Document. */
   public:
   DEFINE_SIZE_ARRAY (0, longMetricZ);
 };

 struct hmtx : hmtxvmtx<hmtx, hhea, HVAR> {
   static constexpr hb_tag_t tableTag = HB_OT_TAG_hmtx;
   static constexpr hb_tag_t variationsTag = HB_OT_TAG_HVAR;
   static constexpr bool is_horizontal = true;
 };
 struct vmtx : hmtxvmtx<vmtx, vhea, VVAR> {
   static constexpr hb_tag_t tableTag = HB_OT_TAG_vmtx;
   static constexpr hb_tag_t variationsTag = HB_OT_TAG_VVAR;
   static constexpr bool is_horizontal = false;
 };

 struct hmtx_accelerator_t : hmtx::accelerator_t {
   hmtx_accelerator_t (hb_face_t *face) : hmtx::accelerator_t (face) {}
 };
 struct vmtx_accelerator_t : vmtx::accelerator_t {
   vmtx_accelerator_t (hb_face_t *face) : vmtx::accelerator_t (face) {}
 };

 } /* namespace OT */


 #endif /* HB_OT_HMTX_TABLE_HH */
	/*
	* 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, Roderick Sheeter
	*/

	#ifndef HB_OT_HMTX_TABLE_HH
	#define HB_OT_HMTX_TABLE_HH

	#include "hb-open-type.hh"
	#include "hb-ot-maxp-table.hh"
	#include "hb-ot-hhea-table.hh"
	#include "hb-ot-var-hvar-table.hh"
	#include "hb-ot-var-mvar-table.hh"
	#include "hb-ot-metrics.hh"

	/*
	* hmtx -- Horizontal Metrics
	* https://docs.microsoft.com/en-us/typography/opentype/spec/hmtx
	* vmtx -- Vertical Metrics
	* https://docs.microsoft.com/en-us/typography/opentype/spec/vmtx
	*/
	#define HB_OT_TAG_hmtx HB_TAG('h','m','t','x')
	#define HB_OT_TAG_vmtx HB_TAG('v','m','t','x')


	HB_INTERNAL bool
	_glyf_get_leading_bearing_with_var_unscaled (hb_font_t font, hb_codepoint_t glyph, bool is_vertical, int lsb);

	HB_INTERNAL unsigned
	_glyf_get_advance_with_var_unscaled (hb_font_t *font, hb_codepoint_t glyph, bool is_vertical);


	namespace OT {


	struct LongMetric
	{
	UFWORD advance; /* Advance width/height. */
	FWORD sb; /* Leading (left/top) side bearing. */
	public:
	DEFINE_SIZE_STATIC (4);
	};


	template <typename T/Data table type/, typename H/Header table type/, typename V/Var table type/>
	struct hmtxvmtx
	{
	bool sanitize (hb_sanitize_context_t *c HB_UNUSED) const
	{
	TRACE_SANITIZE (this);
	/* We don't check for anything specific here. The users of the
	* struct do all the hard work... */
	return_trace (true);
	}

	const hb_hashmap_t<hb_codepoint_t, hb_pair_t<unsigned, int>>* get_mtx_map (const hb_subset_plan_t *plan) const
	{ return T::is_horizontal ? &plan->hmtx_map : &plan->vmtx_map; }

	bool subset_update_header (hb_subset_context_t *c,
	unsigned int num_hmetrics,
	const hb_hashmap_t<hb_codepoint_t, hb_pair_t<unsigned, int>> *mtx_map,
	const hb_map_t *bounds_map) const
	{
	hb_blob_t *src_blob = hb_sanitize_context_t ().reference_table<H> (c->plan->source, H::tableTag);
	hb_blob_t *dest_blob = hb_blob_copy_writable_or_fail (src_blob);
	hb_blob_destroy (src_blob);

	if (unlikely (!dest_blob)) {
	return false;
	}

	unsigned int length;
	H table = (H ) hb_blob_get_data (dest_blob, &length);
	table->numberOfLongMetrics = num_hmetrics;

	#ifndef HB_NO_VAR
	if (c->plan->normalized_coords)
	{
	auto &MVAR = *c->plan->source->table.MVAR;
	if (T::is_horizontal)
	{
	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_HORIZONTAL_CARET_RISE, caretSlopeRise);
	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_HORIZONTAL_CARET_RUN, caretSlopeRun);
	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_HORIZONTAL_CARET_OFFSET, caretOffset);
	}
	else
	{
	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_VERTICAL_CARET_RISE, caretSlopeRise);
	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_VERTICAL_CARET_RUN, caretSlopeRun);
	HB_ADD_MVAR_VAR (HB_OT_METRICS_TAG_VERTICAL_CARET_OFFSET, caretOffset);
	}

	int min_lsb = 0x7FFF;
	int min_rsb = 0x7FFF;
	int max_extent = -0x7FFF;
	unsigned max_adv = 0;
	for (const auto _ : *mtx_map)
	{
	hb_codepoint_t gid = _.first;
	unsigned adv = _.second.first;
	int lsb = _.second.second;
	max_adv = hb_max (max_adv, adv);

	if (bounds_map->has (gid))
	{
	unsigned bound_width = bounds_map->get (gid);
	int rsb = adv - lsb - bound_width;
	int extent = lsb + bound_width;
	min_lsb = hb_min (min_lsb, lsb);
	min_rsb = hb_min (min_rsb, rsb);
	max_extent = hb_max (max_extent, extent);
	}
	}

	table->advanceMax = max_adv;
	if (!bounds_map->is_empty ())
	{
	table->minLeadingBearing = min_lsb;
	table->minTrailingBearing = min_rsb;
	table->maxExtent = max_extent;
	}
	}
	#endif

	bool result = c->plan->add_table (H::tableTag, dest_blob);
	hb_blob_destroy (dest_blob);

	return result;
	}

	template<typename Iterator,
	hb_requires (hb_is_iterator (Iterator))>
	void serialize (hb_serialize_context_t *c,
	Iterator it,
	unsigned num_long_metrics)
	{
	unsigned idx = 0;
	for (auto _ : it)
	{
	if (idx < num_long_metrics)
	{
	LongMetric lm;
	lm.advance = _.first;
	lm.sb = _.second;
	if (unlikely (!c->embed<LongMetric> (&lm))) return;
	}
	else
	{
	FWORD *sb = c->allocate_size<FWORD> (FWORD::static_size);
	if (unlikely (!sb)) return;
	*sb = _.second;
	}
	idx++;
	}
	}

	bool subset (hb_subset_context_t *c) const
	{
	TRACE_SUBSET (this);

	T *table_prime = c->serializer->start_embed <T> ();
	if (unlikely (!table_prime)) return_trace (false);

	accelerator_t _mtx (c->plan->source);
	unsigned num_long_metrics;
	const hb_hashmap_t<hb_codepoint_t, hb_pair_t<unsigned, int>> *mtx_map = get_mtx_map (c->plan);
	{
	/* Determine num_long_metrics to encode. */
	auto& plan = c->plan;

	num_long_metrics = plan->num_output_glyphs ();
	unsigned int last_advance = get_new_gid_advance_unscaled (plan, mtx_map, num_long_metrics - 1, _mtx);
	while (num_long_metrics > 1 &&
	last_advance == get_new_gid_advance_unscaled (plan, mtx_map, num_long_metrics - 2, _mtx))
	{
	num_long_metrics--;
	}
	}

	auto it =
	+ hb_range (c->plan->num_output_glyphs ())
	\| hb_map ([c, &_mtx, mtx_map] (unsigned _)
	{
	if (!mtx_map->has (_))
	{
	hb_codepoint_t old_gid;
	if (!c->plan->old_gid_for_new_gid (_, &old_gid))
	return hb_pair (0u, 0);
	int lsb = 0;
	(void) _mtx.get_leading_bearing_without_var_unscaled (old_gid, &lsb);
	return hb_pair (_mtx.get_advance_without_var_unscaled (old_gid), +lsb);
	}
	return mtx_map->get (_);
	})
	;

	table_prime->serialize (c->serializer, it, num_long_metrics);

	if (unlikely (c->serializer->in_error ()))
	return_trace (false);

	// Amend header num hmetrics
	if (unlikely (!subset_update_header (c, num_long_metrics, mtx_map,
	T::is_horizontal ? &c->plan->bounds_width_map : &c->plan->bounds_height_map)))
	return_trace (false);

	return_trace (true);
	}

	struct accelerator_t
	{
	friend struct hmtxvmtx;

	accelerator_t (hb_face_t *face)
	{
	table = hb_sanitize_context_t ().reference_table<hmtxvmtx> (face, T::tableTag);
	var_table = hb_sanitize_context_t ().reference_table<V> (face, T::variationsTag);

	default_advance = T::is_horizontal ? hb_face_get_upem (face) / 2 : hb_face_get_upem (face);

	/* Populate count variables and sort them out as we go */

	unsigned int len = table.get_length ();
	if (len & 1)
	len--;

	num_long_metrics = T::is_horizontal ?
	face->table.hhea->numberOfLongMetrics :
	#ifndef HB_NO_VERTICAL
	face->table.vhea->numberOfLongMetrics
	#else
	0
	#endif
	;
	if (unlikely (num_long_metrics * 4 > len))
	num_long_metrics = len / 4;
	len -= num_long_metrics * 4;

	num_bearings = face->table.maxp->get_num_glyphs ();

	if (unlikely (num_bearings < num_long_metrics))
	num_bearings = num_long_metrics;
	if (unlikely ((num_bearings - num_long_metrics) * 2 > len))
	num_bearings = num_long_metrics + len / 2;
	len -= (num_bearings - num_long_metrics) * 2;

	/* We MUST set num_bearings to zero if num_long_metrics is zero.
	* Our get_advance() depends on that. */
	if (unlikely (!num_long_metrics))
	num_bearings = num_long_metrics = 0;

	num_advances = num_bearings + len / 2;
	num_glyphs = face->get_num_glyphs ();
	if (num_glyphs < num_advances)
	num_glyphs = num_advances;
	}
	~accelerator_t ()
	{
	table.destroy ();
	var_table.destroy ();
	}

	bool has_data () const { return (bool) num_bearings; }

	bool get_leading_bearing_without_var_unscaled (hb_codepoint_t glyph,
	int *lsb) const
	{
	if (glyph < num_long_metrics)
	{
	*lsb = table->longMetricZ[glyph].sb;
	return true;
	}

	if (unlikely (glyph >= num_bearings))
	return false;

	const FWORD bearings = (const FWORD ) &table->longMetricZ[num_long_metrics];
	*lsb = bearings[glyph - num_long_metrics];
	return true;
	}

	bool get_leading_bearing_with_var_unscaled (hb_font_t *font,
	hb_codepoint_t glyph,
	int *lsb) const
	{
	if (!font->num_coords)
	return get_leading_bearing_without_var_unscaled (glyph, lsb);

	#ifndef HB_NO_VAR
	float delta;
	if (var_table->get_lsb_delta_unscaled (glyph, font->coords, font->num_coords, &delta) &&
	get_leading_bearing_without_var_unscaled (glyph, lsb))
	{
	*lsb += roundf (delta);
	return true;
	}

	return _glyf_get_leading_bearing_with_var_unscaled (font, glyph, T::tableTag == HB_OT_TAG_vmtx, lsb);
	#else
	return false;
	#endif
	}

	unsigned int get_advance_without_var_unscaled (hb_codepoint_t glyph) const
	{
	/* OpenType case. */
	if (glyph < num_bearings)
	return table->longMetricZ[hb_min (glyph, (uint32_t) num_long_metrics - 1)].advance;

	/* If num_advances is zero, it means we don't have the metrics table
	* for this direction: return default advance. Otherwise, there's a
	* well-defined answer. */
	if (unlikely (!num_advances))
	return default_advance;

	#ifdef HB_NO_BEYOND_64K
	return 0;
	#endif

	if (unlikely (glyph >= num_glyphs))
	return 0;

	/* num_bearings <= glyph < num_glyphs;
	* num_bearings <= num_advances */

	if (num_bearings == num_advances)
	return get_advance_without_var_unscaled (num_bearings - 1);

	const FWORD bearings = (const FWORD ) &table->longMetricZ[num_long_metrics];
	const UFWORD advances = (const UFWORD ) &bearings[num_bearings - num_long_metrics];

	return advances[hb_min (glyph - num_bearings, num_advances - num_bearings - 1)];
	}

	unsigned get_advance_with_var_unscaled (hb_codepoint_t glyph,
	hb_font_t *font,
	VariationStore::cache_t *store_cache = nullptr) const
	{
	unsigned int advance = get_advance_without_var_unscaled (glyph);

	#ifndef HB_NO_VAR
	if (unlikely (glyph >= num_bearings) \|\| !font->num_coords)
	return advance;

	if (var_table.get_length ())
	return advance + roundf (var_table->get_advance_delta_unscaled (glyph,
	font->coords, font->num_coords,
	store_cache));

	return _glyf_get_advance_with_var_unscaled (font, glyph, T::tableTag == HB_OT_TAG_vmtx);
	#else
	return advance;
	#endif
	}

	protected:
	// 0 <= num_long_metrics <= num_bearings <= num_advances <= num_glyphs
	unsigned num_long_metrics;
	unsigned num_bearings;
	unsigned num_advances;
	unsigned num_glyphs;

	unsigned int default_advance;

	public:
	hb_blob_ptr_t<hmtxvmtx> table;
	hb_blob_ptr_t<V> var_table;
	};

	/* get advance: when no variations, call get_advance_without_var_unscaled.
	* when there're variations, get advance value from mtx_map in subset_plan*/
	unsigned get_new_gid_advance_unscaled (const hb_subset_plan_t *plan,
	const hb_hashmap_t<hb_codepoint_t, hb_pair_t<unsigned, int>> *mtx_map,
	unsigned new_gid,
	const accelerator_t &_mtx) const
	{
	if (mtx_map->is_empty ())
	{
	hb_codepoint_t old_gid = 0;
	return plan->old_gid_for_new_gid (new_gid, &old_gid) ?
	_mtx.get_advance_without_var_unscaled (old_gid) : 0;
	}
	return mtx_map->get (new_gid).first;
	}

	protected:
	UnsizedArrayOf<LongMetric>
	longMetricZ; /* Paired advance width and leading
	* bearing values for each glyph. The
	* value numOfHMetrics comes from
	* the 'hhea' table. If the font is
	* monospaced, only one entry need
	* be in the array, but that entry is
	* required. The last entry applies to
	* all subsequent glyphs. */
	/UnsizedArrayOf<FWORD> leadingBearingX;/
	/* Here the advance is assumed
	* to be the same as the advance
	* for the last entry above. The
	* number of entries in this array is
	* derived from numGlyphs (from 'maxp'
	* table) minus numberOfLongMetrics.
	* This generally is used with a run
	* of monospaced glyphs (e.g., Kanji
	* fonts or Courier fonts). Only one
	* run is allowed and it must be at
	* the end. This allows a monospaced
	* font to vary the side bearing
	* values for each glyph. */
	/UnsizedArrayOf<UFWORD>advancesX;/
	/* TODO Document. */
	public:
	DEFINE_SIZE_ARRAY (0, longMetricZ);
	};

	struct hmtx : hmtxvmtx<hmtx, hhea, HVAR> {
	static constexpr hb_tag_t tableTag = HB_OT_TAG_hmtx;
	static constexpr hb_tag_t variationsTag = HB_OT_TAG_HVAR;
	static constexpr bool is_horizontal = true;
	};
	struct vmtx : hmtxvmtx<vmtx, vhea, VVAR> {
	static constexpr hb_tag_t tableTag = HB_OT_TAG_vmtx;
	static constexpr hb_tag_t variationsTag = HB_OT_TAG_VVAR;
	static constexpr bool is_horizontal = false;
	};

	struct hmtx_accelerator_t : hmtx::accelerator_t {
	hmtx_accelerator_t (hb_face_t *face) : hmtx::accelerator_t (face) {}
	};
	struct vmtx_accelerator_t : vmtx::accelerator_t {
	vmtx_accelerator_t (hb_face_t *face) : vmtx::accelerator_t (face) {}
	};

	} /* namespace OT */


	#endif /* HB_OT_HMTX_TABLE_HH */