hb-ot-hmtx-table.hh

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/*
 * 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-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 int
_glyf_get_side_bearing_var (hb_font_t *font, hb_codepoint_t glyph, bool is_vertical);
 
HB_INTERNAL unsigned
_glyf_get_advance_var (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, typename H>
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);
  }
 
 
  bool subset_update_header (hb_subset_plan_t *plan,
                 unsigned int num_hmetrics) const
  {
    hb_blob_t *src_blob = hb_sanitize_context_t ().reference_table<H> (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;
 
    bool result = 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;
    {
      /* Determine num_long_metrics to encode. */
      auto& plan = c->plan;
      num_long_metrics = plan->num_output_glyphs ();
      hb_codepoint_t old_gid = 0;
      unsigned int last_advance = plan->old_gid_for_new_gid (num_long_metrics - 1, &old_gid) ? _mtx.get_advance (old_gid) : 0;
      while (num_long_metrics > 1 &&
         last_advance == (plan->old_gid_for_new_gid (num_long_metrics - 2, &old_gid) ? _mtx.get_advance (old_gid) : 0))
      {
    num_long_metrics--;
      }
    }
 
    auto it =
    + hb_range (c->plan->num_output_glyphs ())
    | hb_map ([c, &_mtx] (unsigned _)
          {
        hb_codepoint_t old_gid;
        if (!c->plan->old_gid_for_new_gid (_, &old_gid))
          return hb_pair (0u, 0);
        return hb_pair (_mtx.get_advance (old_gid), _mtx.get_side_bearing (old_gid));
          })
    ;
 
    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->plan, num_long_metrics)))
      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<HVARVVAR> (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; }
 
    int get_side_bearing (hb_codepoint_t glyph) const
    {
      if (glyph < num_long_metrics)
    return table->longMetricZ[glyph].sb;
 
      if (unlikely (glyph >= num_bearings))
    return 0;
 
      const FWORD *bearings = (const FWORD *) &table->longMetricZ[num_long_metrics];
      return bearings[glyph - num_long_metrics];
    }
 
    int get_side_bearing (hb_font_t *font, hb_codepoint_t glyph) const
    {
      int side_bearing = get_side_bearing (glyph);
 
#ifndef HB_NO_VAR
      if (unlikely (glyph >= num_bearings) || !font->num_coords)
    return side_bearing;
 
      if (var_table.get_length ())
    return side_bearing + var_table->get_side_bearing_var (glyph, font->coords, font->num_coords); // TODO Optimize?!
 
      return _glyf_get_side_bearing_var (font, glyph, T::tableTag == HB_OT_TAG_vmtx);
#else
      return side_bearing;
#endif
    }
 
    unsigned int get_advance (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_BORING_EXPANSION
      return 0;
#endif
 
      if (unlikely (glyph >= num_glyphs))
        return 0;
 
      /* num_bearings <= glyph < num_glyphs;
       * num_bearings <= num_advances */
 
      /* TODO Optimize */
 
      if (num_bearings == num_advances)
        return get_advance (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 int get_advance (hb_codepoint_t  glyph,
                  hb_font_t      *font) const
    {
      unsigned int advance = get_advance (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_var (glyph, font)); // TODO Optimize?!
 
      return _glyf_get_advance_var (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;
 
    private:
    hb_blob_ptr_t<hmtxvmtx> table;
    hb_blob_ptr_t<HVARVVAR> var_table;
  };
 
  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> {
  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> {
  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 */