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_KERN_HH
  28 #define HB_KERN_HH
  29 
  30 #include "hb-open-type.hh"
  31 #include "hb-aat-layout-common.hh"
  32 #include "hb-ot-layout-gpos-table.hh"
  33 
  34 
  35 namespace OT {
  36 
  37 
  38 template <typename Driver>
  39 struct hb_kern_machine_t
  40 {
  41   hb_kern_machine_t (const Driver &driver_,
  42                      bool crossStream_ = false) :
  43                        driver (driver_),
  44                        crossStream (crossStream_) {}
  45 
  46   HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW
  47   void kern (hb_font_t   *font,
  48              hb_buffer_t *buffer,
  49              hb_mask_t    kern_mask,
  50              bool         scale = true) const
  51   {
  52     OT::hb_ot_apply_context_t c (1, font, buffer);
  53     c.set_lookup_mask (kern_mask);
  54     c.set_lookup_props (OT::LookupFlag::IgnoreMarks);
  55     OT::hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c.iter_input;
  56     skippy_iter.init (&c);
  57 
  58     bool horizontal = HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction);
  59     unsigned int count = buffer->len;
  60     hb_glyph_info_t *info = buffer->info;
  61     hb_glyph_position_t *pos = buffer->pos;
  62     for (unsigned int idx = 0; idx < count;)
  63     {
  64       if (!(info[idx].mask & kern_mask))
  65       {
  66         idx++;
  67         continue;
  68       }
  69 
  70       skippy_iter.reset (idx, 1);
  71       if (!skippy_iter.next ())
  72       {
  73         idx++;
  74         continue;
  75       }
  76 
  77       unsigned int i = idx;
  78       unsigned int j = skippy_iter.idx;
  79 
  80       hb_position_t kern = driver.get_kerning (info[i].codepoint,
  81                                                info[j].codepoint);
  82 
  83 
  84       if (likely (!kern))
  85         goto skip;
  86 
  87       if (horizontal)
  88       {
  89         if (scale)
  90           kern = font->em_scale_x (kern);
  91         if (crossStream)
  92         {
  93           pos[j].y_offset = kern;
  94           buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
  95         }
  96         else
  97         {
  98           hb_position_t kern1 = kern >> 1;
  99           hb_position_t kern2 = kern - kern1;
 100           pos[i].x_advance += kern1;
 101           pos[j].x_advance += kern2;
 102           pos[j].x_offset += kern2;
 103         }
 104       }
 105       else
 106       {
 107         if (scale)
 108           kern = font->em_scale_y (kern);
 109         if (crossStream)
 110         {
 111           pos[j].x_offset = kern;
 112           buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
 113         }
 114         else
 115         {
 116           hb_position_t kern1 = kern >> 1;
 117           hb_position_t kern2 = kern - kern1;
 118           pos[i].y_advance += kern1;
 119           pos[j].y_advance += kern2;
 120           pos[j].y_offset += kern2;
 121         }
 122       }
 123 
 124       buffer->unsafe_to_break (i, j + 1);
 125 
 126     skip:
 127       idx = skippy_iter.idx;
 128     }
 129   }
 130 
 131   const Driver &driver;
 132   bool crossStream;
 133 };
 134 
 135 
 136 } /* namespace OT */
 137 
 138 
 139 #endif /* HB_KERN_HH */