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      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 */
    140