1 /*

     2  * Copyright © 2018  Ebrahim Byagowi

     3  * Copyright © 2018  Google, Inc.

     4  *

     5  *  This is part of HarfBuzz, a text shaping library.

     6  *

     7  * Permission is hereby granted, without written agreement and without

     8  * license or royalty fees, to use, copy, modify, and distribute this

     9  * software and its documentation for any purpose, provided that the

    10  * above copyright notice and the following two paragraphs appear in

    11  * all copies of this software.

    12  *

    13  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR

    14  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES

    15  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN

    16  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH

    17  * DAMAGE.

    18  *

    19  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,

    20  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

    21  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS

    22  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO

    23  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

    24  *

    25  * Google Author(s): Behdad Esfahbod

    26  */

    27 

    28 #ifndef HB_AAT_LAYOUT_TRAK_TABLE_HH

    29 #define HB_AAT_LAYOUT_TRAK_TABLE_HH

    30 

    31 #include "hb-aat-layout-common.hh"

    32 #include "hb-ot-layout.hh"

    33 #include "hb-open-type.hh"

    34 

    35 /*

    36  * trak -- Tracking

    37  * https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6trak.html

    38  */

    39 #define HB_AAT_TAG_trak HB_TAG('t','r','a','k')

    40 

    41 

    42 namespace AAT {

    43 

    44 

    45 struct TrackTableEntry

    46 {

    47   friend struct TrackData;

    48 

    49   float get_track_value () const { return track.to_float (); }

    50 

    51   int get_value (const void *base, unsigned int index,

    52                  unsigned int table_size) const

    53   { return (base+valuesZ).as_array (table_size)[index]; }

    54 

    55   public:

    56   bool sanitize (hb_sanitize_context_t *c, const void *base,

    57                  unsigned int table_size) const

    58   {

    59     TRACE_SANITIZE (this);

    60     return_trace (likely (c->check_struct (this) &&

    61                           (valuesZ.sanitize (c, base, table_size))));

    62   }

    63 

    64   protected:

    65   Fixed         track;          /* Track value for this record. */

    66   NameID        trackNameID;    /* The 'name' table index for this track.

    67                                  * (a short word or phrase like "loose"

    68                                  * or "very tight") */

    69   NNOffsetTo<UnsizedArrayOf<FWORD> >

    70                 valuesZ;        /* Offset from start of tracking table to

    71                                  * per-size tracking values for this track. */

    72 

    73   public:

    74   DEFINE_SIZE_STATIC (8);

    75 };

    76 

    77 struct TrackData

    78 {

    79   float interpolate_at (unsigned int idx,

    80                         float target_size,

    81                         const TrackTableEntry &trackTableEntry,

    82                         const void *base) const

    83   {

    84     unsigned int sizes = nSizes;

    85     hb_array_t<const Fixed> size_table ((base+sizeTable).arrayZ, sizes);

    86 

    87     float s0 = size_table[idx].to_float ();

    88     float s1 = size_table[idx + 1].to_float ();

    89     float t = unlikely (s0 == s1) ? 0.f : (target_size - s0) / (s1 - s0);

    90     return t * trackTableEntry.get_value (base, idx + 1, sizes) +

    91            (1.f - t) * trackTableEntry.get_value (base, idx, sizes);

    92   }

    93 

    94   int get_tracking (const void *base, float ptem) const

    95   {

    96     /* CoreText points are CSS pixels (96 per inch),

    97      * NOT typographic points (72 per inch).

    98      *

    99      * https://developer.apple.com/library/content/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/Explained/Explained.html

   100      */

   101     float csspx = ptem * 96.f / 72.f;

   102 

   103     /*

   104      * Choose track.

   105      */

   106     const TrackTableEntry *trackTableEntry = nullptr;

   107     unsigned int count = nTracks;

   108     for (unsigned int i = 0; i < count; i++)

   109     {

   110       /* Note: Seems like the track entries are sorted by values.  But the

   111        * spec doesn't explicitly say that.  It just mentions it in the example. */

   112 

   113       /* For now we only seek for track entries with zero tracking value */

   114 

   115       if (trackTable[i].get_track_value () == 0.f)

   116       {

   117         trackTableEntry = &trackTable[i];

   118         break;

   119       }

   120     }

   121     if (!trackTableEntry) return 0.;

   122 

   123     /*

   124      * Choose size.

   125      */

   126     unsigned int sizes = nSizes;

   127     if (!sizes) return 0.;

   128     if (sizes == 1) return trackTableEntry->get_value (base, 0, sizes);

   129 

   130     hb_array_t<const Fixed> size_table ((base+sizeTable).arrayZ, sizes);

   131     unsigned int size_index;

   132     for (size_index = 0; size_index < sizes - 1; size_index++)

   133       if (size_table[size_index].to_float () >= csspx)

   134         break;

   135 

   136     return round (interpolate_at (size_index ? size_index - 1 : 0, csspx,

   137                                   *trackTableEntry, base));

   138   }

   139 

   140   bool sanitize (hb_sanitize_context_t *c, const void *base) const

   141   {

   142     TRACE_SANITIZE (this);

   143     return_trace (likely (c->check_struct (this) &&

   144                           sizeTable.sanitize (c, base, nSizes) &&

   145                           trackTable.sanitize (c, nTracks, base, nSizes)));

   146   }

   147 

   148   protected:

   149   HBUINT16      nTracks;        /* Number of separate tracks included in this table. */

   150   HBUINT16      nSizes;         /* Number of point sizes included in this table. */

   151   LOffsetTo<UnsizedArrayOf<Fixed>, false>

   152                 sizeTable;      /* Offset from start of the tracking table to

   153                                  * Array[nSizes] of size values.. */

   154   UnsizedArrayOf<TrackTableEntry>

   155                 trackTable;     /* Array[nTracks] of TrackTableEntry records. */

   156 

   157   public:

   158   DEFINE_SIZE_ARRAY (8, trackTable);

   159 };

   160 

   161 struct trak

   162 {

   163   static constexpr hb_tag_t tableTag = HB_AAT_TAG_trak;

   164 

   165   bool has_data () const { return version.to_int (); }

   166 

   167   bool apply (hb_aat_apply_context_t *c) const

   168   {

   169     TRACE_APPLY (this);

   170 

   171     hb_mask_t trak_mask = c->plan->trak_mask;

   172 

   173     const float ptem = c->font->ptem;

   174     if (unlikely (ptem <= 0.f))

   175       return_trace (false);

   176 

   177     hb_buffer_t *buffer = c->buffer;

   178     if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))

   179     {

   180       const TrackData &trackData = this+horizData;

   181       int tracking = trackData.get_tracking (this, ptem);

   182       hb_position_t offset_to_add = c->font->em_scalef_x (tracking / 2);

   183       hb_position_t advance_to_add = c->font->em_scalef_x (tracking);

   184       foreach_grapheme (buffer, start, end)

   185       {

   186         if (!(buffer->info[start].mask & trak_mask)) continue;

   187         buffer->pos[start].x_advance += advance_to_add;

   188         buffer->pos[start].x_offset += offset_to_add;

   189       }

   190     }

   191     else

   192     {

   193       const TrackData &trackData = this+vertData;

   194       int tracking = trackData.get_tracking (this, ptem);

   195       hb_position_t offset_to_add = c->font->em_scalef_y (tracking / 2);

   196       hb_position_t advance_to_add = c->font->em_scalef_y (tracking);

   197       foreach_grapheme (buffer, start, end)

   198       {

   199         if (!(buffer->info[start].mask & trak_mask)) continue;

   200         buffer->pos[start].y_advance += advance_to_add;

   201         buffer->pos[start].y_offset += offset_to_add;

   202       }

   203     }

   204 

   205     return_trace (true);

   206   }

   207 

   208   bool sanitize (hb_sanitize_context_t *c) const

   209   {

   210     TRACE_SANITIZE (this);

   211 

   212     return_trace (likely (c->check_struct (this) &&

   213                           version.major == 1 &&

   214                           horizData.sanitize (c, this, this) &&

   215                           vertData.sanitize (c, this, this)));

   216   }

   217 

   218   protected:

   219   FixedVersion<>version;        /* Version of the tracking table

   220                                          * (0x00010000u for version 1.0). */

   221   HBUINT16      format;         /* Format of the tracking table (set to 0). */

   222   OffsetTo<TrackData>

   223                 horizData;      /* Offset from start of tracking table to TrackData

   224                                  * for horizontal text (or 0 if none). */

   225   OffsetTo<TrackData>

   226                 vertData;       /* Offset from start of tracking table to TrackData

   227                                  * for vertical text (or 0 if none). */

   228   HBUINT16      reserved;       /* Reserved. Set to 0. */

   229 

   230   public:

   231   DEFINE_SIZE_STATIC (12);

   232 };

   233 

   234 } /* namespace AAT */

   235 

   236 

   237 #endif /* HB_AAT_LAYOUT_TRAK_TABLE_HH */