hb-ot-var-avar-table.hh

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/*
 * Copyright © 2017  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
 */
 
#ifndef HB_OT_VAR_AVAR_TABLE_HH
#define HB_OT_VAR_AVAR_TABLE_HH
 
#include "hb-open-type.hh"
 
/*
 * avar -- Axis Variations
 * https://docs.microsoft.com/en-us/typography/opentype/spec/avar
 */
 
#define HB_OT_TAG_avar HB_TAG('a','v','a','r')
 
 
namespace OT {
 
 
struct AxisValueMap
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }
 
  public:
  F2DOT14   coords[2];
//   F2DOT14    fromCoord;  /* A normalized coordinate value obtained using
//               * default normalization. */
//   F2DOT14    toCoord;    /* The modified, normalized coordinate value. */
 
  public:
  DEFINE_SIZE_STATIC (4);
};
 
struct SegmentMaps : Array16Of<AxisValueMap>
{
  int map (int value, unsigned int from_offset = 0, unsigned int to_offset = 1) const
  {
#define fromCoord coords[from_offset]
#define toCoord coords[to_offset]
    /* The following special-cases are not part of OpenType, which requires
     * that at least -1, 0, and +1 must be mapped. But we include these as
     * part of a better error recovery scheme. */
    if (len < 2)
    {
      if (!len)
    return value;
      else /* len == 1*/
    return value - arrayZ[0].fromCoord + arrayZ[0].toCoord;
    }
 
    if (value <= arrayZ[0].fromCoord)
      return value - arrayZ[0].fromCoord + arrayZ[0].toCoord;
 
    unsigned int i;
    unsigned int count = len - 1;
    for (i = 1; i < count && value > arrayZ[i].fromCoord; i++)
      ;
 
    if (value >= arrayZ[i].fromCoord)
      return value - arrayZ[i].fromCoord + arrayZ[i].toCoord;
 
    if (unlikely (arrayZ[i-1].fromCoord == arrayZ[i].fromCoord))
      return arrayZ[i-1].toCoord;
 
    int denom = arrayZ[i].fromCoord - arrayZ[i-1].fromCoord;
    return roundf (arrayZ[i-1].toCoord + ((float) (arrayZ[i].toCoord - arrayZ[i-1].toCoord) *
                      (value - arrayZ[i-1].fromCoord)) / denom);
#undef toCoord
#undef fromCoord
  }
 
  int unmap (int value) const { return map (value, 1, 0); }
 
  public:
  DEFINE_SIZE_ARRAY (2, *this);
};
 
struct avar
{
  static constexpr hb_tag_t tableTag = HB_OT_TAG_avar;
 
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    if (unlikely (!(version.sanitize (c) &&
            version.major == 1 &&
            c->check_struct (this))))
      return_trace (false);
 
    const SegmentMaps *map = &firstAxisSegmentMaps;
    unsigned int count = axisCount;
    for (unsigned int i = 0; i < count; i++)
    {
      if (unlikely (!map->sanitize (c)))
    return_trace (false);
      map = &StructAfter<SegmentMaps> (*map);
    }
 
    return_trace (true);
  }
 
  void map_coords (int *coords, unsigned int coords_length) const
  {
    unsigned int count = hb_min (coords_length, axisCount);
 
    const SegmentMaps *map = &firstAxisSegmentMaps;
    for (unsigned int i = 0; i < count; i++)
    {
      coords[i] = map->map (coords[i]);
      map = &StructAfter<SegmentMaps> (*map);
    }
  }
 
  void unmap_coords (int *coords, unsigned int coords_length) const
  {
    unsigned int count = hb_min (coords_length, axisCount);
 
    const SegmentMaps *map = &firstAxisSegmentMaps;
    for (unsigned int i = 0; i < count; i++)
    {
      coords[i] = map->unmap (coords[i]);
      map = &StructAfter<SegmentMaps> (*map);
    }
  }
 
  protected:
  FixedVersion<>version;    /* Version of the avar table
                 * initially set to 0x00010000u */
  HBUINT16  reserved;   /* This field is permanently reserved. Set to 0. */
  HBUINT16  axisCount;  /* The number of variation axes in the font. This
                 * must be the same number as axisCount in the
                 * 'fvar' table. */
  SegmentMaps   firstAxisSegmentMaps;
 
  public:
  DEFINE_SIZE_MIN (8);
};
 
} /* namespace OT */
 
 
#endif /* HB_OT_VAR_AVAR_TABLE_HH */