harfbuzz/src/hb-ot-var-avar-table.hh

/*
 * 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"
#include "hb-ot-var-common.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 {


/* "Spec": https://github.com/be-fonts/boring-expansion-spec/issues/14 */
struct avarV2Tail
{
  friend struct avar;

  bool sanitize (hb_sanitize_context_t *c,
		 const void *base) const
  {
    TRACE_SANITIZE (this);
    return_trace (varIdxMap.sanitize (c, base) &&
		  varStore.sanitize (c, base));
  }

  protected:
  Offset32To<DeltaSetIndexMap>	varIdxMap;	/* Offset from the beginning of 'avar' table. */
  Offset32To<VariationStore>	varStore;	/* Offset from the beginning of 'avar' table. */

  public:
  DEFINE_SIZE_STATIC (8);
};


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].to_int ()
#define toCoord coords[to_offset].to_int ()
    /* 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 has_data () const { return version.to_int (); }

  const SegmentMaps* get_segment_maps () const
  { return &firstAxisSegmentMaps; }

  unsigned get_axis_count () const
  { return axisCount; }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    if (!(version.sanitize (c) &&
	  (version.major == 1
#ifndef HB_NO_AVAR2
	   || version.major == 2
#endif
	   ) &&
	  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);
    }

#ifndef HB_NO_AVAR2
    if (version.major < 2)
      return_trace (true);

    const auto &v2 = * (const avarV2Tail *) map;
    if (unlikely (!v2.sanitize (c, this)))
      return_trace (false);
#endif

    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);
    }

#ifndef HB_NO_AVAR2
    if (version.major < 2)
      return;

    for (; count < axisCount; count++)
      map = &StructAfter<SegmentMaps> (*map);

    const auto &v2 = * (const avarV2Tail *) map;

    const auto &varidx_map = this+v2.varIdxMap;
    const auto &var_store = this+v2.varStore;
    auto *var_store_cache = var_store.create_cache ();

    hb_vector_t<int> out;
    out.alloc (coords_length);
    for (unsigned i = 0; i < coords_length; i++)
    {
      int v = coords[i];
      uint32_t varidx = varidx_map.map (i);
      float delta = var_store.get_delta (varidx, coords, coords_length, var_store_cache);
      v += roundf (delta);
      v = hb_clamp (v, -(1<<14), +(1<<14));
      out.push (v);
    }
    for (unsigned i = 0; i < coords_length; i++)
      coords[i] = out[i];

    OT::VariationStore::destroy_cache (var_store_cache);
#endif
  }

  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 */