1 /*
   2  * Copyright © 2017  Google, Inc.
   3  *
   4  *  This is part of HarfBuzz, a text shaping library.
   5  *
   6  * Permission is hereby granted, without written agreement and without
   7  * license or royalty fees, to use, copy, modify, and distribute this
   8  * software and its documentation for any purpose, provided that the
   9  * above copyright notice and the following two paragraphs appear in
  10  * all copies of this software.
  11  *
  12  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  13  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  14  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  15  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  16  * DAMAGE.
  17  *
  18  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  19  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  20  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  21  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  22  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  23  *
  24  * Google Author(s): Behdad Esfahbod
  25  */
  26 
  27 #ifndef HB_OT_VAR_AVAR_TABLE_HH
  28 #define HB_OT_VAR_AVAR_TABLE_HH
  29 
  30 #include "hb-open-type.hh"
  31 
  32 /*
  33  * avar -- Axis Variations
  34  * https://docs.microsoft.com/en-us/typography/opentype/spec/avar
  35  */
  36 
  37 #define HB_OT_TAG_avar HB_TAG('a','v','a','r')
  38 
  39 
  40 namespace OT {
  41 
  42 
  43 struct AxisValueMap
  44 {
  45   bool sanitize (hb_sanitize_context_t *c) const
  46   {
  47     TRACE_SANITIZE (this);
  48     return_trace (c->check_struct (this));
  49   }
  50 
  51   public:
  52   F2DOT14       fromCoord;      /* A normalized coordinate value obtained using
  53                                  * default normalization. */
  54   F2DOT14       toCoord;        /* The modified, normalized coordinate value. */
  55 
  56   public:
  57   DEFINE_SIZE_STATIC (4);
  58 };
  59 
  60 struct SegmentMaps : ArrayOf<AxisValueMap>
  61 {
  62   int map (int value) const
  63   {
  64     /* The following special-cases are not part of OpenType, which requires
  65      * that at least -1, 0, and +1 must be mapped. But we include these as
  66      * part of a better error recovery scheme. */
  67 
  68     if (len < 2)
  69     {
  70       if (!len)
  71         return value;
  72       else /* len == 1*/
  73         return value - arrayZ[0].fromCoord + arrayZ[0].toCoord;
  74     }
  75 
  76     if (value <= arrayZ[0].fromCoord)
  77       return value - arrayZ[0].fromCoord + arrayZ[0].toCoord;
  78 
  79     unsigned int i;
  80     unsigned int count = len;
  81     for (i = 1; i < count && value > arrayZ[i].fromCoord; i++)
  82       ;
  83 
  84     if (value >= arrayZ[i].fromCoord)
  85       return value - arrayZ[i].fromCoord + arrayZ[i].toCoord;
  86 
  87     if (unlikely (arrayZ[i-1].fromCoord == arrayZ[i].fromCoord))
  88       return arrayZ[i-1].toCoord;
  89 
  90     int denom = arrayZ[i].fromCoord - arrayZ[i-1].fromCoord;
  91     return arrayZ[i-1].toCoord +
  92            ((arrayZ[i].toCoord - arrayZ[i-1].toCoord) *
  93             (value - arrayZ[i-1].fromCoord) + denom/2) / denom;
  94   }
  95 
  96   public:
  97   DEFINE_SIZE_ARRAY (2, *this);
  98 };
  99 
 100 struct avar
 101 {
 102   static constexpr hb_tag_t tableTag = HB_OT_TAG_avar;
 103 
 104   bool sanitize (hb_sanitize_context_t *c) const
 105   {
 106     TRACE_SANITIZE (this);
 107     if (unlikely (!(version.sanitize (c) &&
 108                     version.major == 1 &&
 109                     c->check_struct (this))))
 110       return_trace (false);
 111 
 112     const SegmentMaps *map = &firstAxisSegmentMaps;
 113     unsigned int count = axisCount;
 114     for (unsigned int i = 0; i < count; i++)
 115     {
 116       if (unlikely (!map->sanitize (c)))
 117         return_trace (false);
 118       map = &StructAfter<SegmentMaps> (*map);
 119     }
 120 
 121     return_trace (true);
 122   }
 123 
 124   void map_coords (int *coords, unsigned int coords_length) const
 125   {
 126     unsigned int count = MIN<unsigned int> (coords_length, axisCount);
 127 
 128     const SegmentMaps *map = &firstAxisSegmentMaps;
 129     for (unsigned int i = 0; i < count; i++)
 130     {
 131       coords[i] = map->map (coords[i]);
 132       map = &StructAfter<SegmentMaps> (*map);
 133     }
 134   }
 135 
 136   protected:
 137   FixedVersion<>version;        /* Version of the avar table
 138                                  * initially set to 0x00010000u */
 139   HBUINT16      reserved;       /* This field is permanently reserved. Set to 0. */
 140   HBUINT16      axisCount;      /* The number of variation axes in the font. This
 141                                  * must be the same number as axisCount in the
 142                                  * 'fvar' table. */
 143   SegmentMaps   firstAxisSegmentMaps;
 144 
 145   public:
 146   DEFINE_SIZE_MIN (8);
 147 };
 148 
 149 } /* namespace OT */
 150 
 151 
 152 #endif /* HB_OT_VAR_AVAR_TABLE_HH */