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 {
hb_kern_machine_tOT::hb_kern_machine_t41   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
kernOT::hb_kern_machine_t47   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     auto &skippy_iter = c.iter_input;
56 
57     bool horizontal = HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction);
58     unsigned int count = buffer->len;
59     hb_glyph_info_t *info = buffer->info;
60     hb_glyph_position_t *pos = buffer->pos;
61     for (unsigned int idx = 0; idx < count;)
62     {
63       if (!(info[idx].mask & kern_mask))
64       {
65 	idx++;
66 	continue;
67       }
68 
69       skippy_iter.reset (idx, 1);
70       if (!skippy_iter.next ())
71       {
72 	idx++;
73 	continue;
74       }
75 
76       unsigned int i = idx;
77       unsigned int j = skippy_iter.idx;
78 
79       hb_position_t kern = driver.get_kerning (info[i].codepoint,
80 					       info[j].codepoint);
81 
82 
83       if (likely (!kern))
84 	goto skip;
85 
86       if (horizontal)
87       {
88 	if (scale)
89 	  kern = font->em_scale_x (kern);
90 	if (crossStream)
91 	{
92 	  pos[j].y_offset = kern;
93 	  buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
94 	}
95 	else
96 	{
97 	  hb_position_t kern1 = kern >> 1;
98 	  hb_position_t kern2 = kern - kern1;
99 	  pos[i].x_advance += kern1;
100 	  pos[j].x_advance += kern2;
101 	  pos[j].x_offset += kern2;
102 	}
103       }
104       else
105       {
106 	if (scale)
107 	  kern = font->em_scale_y (kern);
108 	if (crossStream)
109 	{
110 	  pos[j].x_offset = kern;
111 	  buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
112 	}
113 	else
114 	{
115 	  hb_position_t kern1 = kern >> 1;
116 	  hb_position_t kern2 = kern - kern1;
117 	  pos[i].y_advance += kern1;
118 	  pos[j].y_advance += kern2;
119 	  pos[j].y_offset += kern2;
120 	}
121       }
122 
123       buffer->unsafe_to_break (i, j + 1);
124 
125     skip:
126       idx = skippy_iter.idx;
127     }
128   }
129 
130   const Driver &driver;
131   bool crossStream;
132 };
133 
134 
135 } /* namespace OT */
136 
137 
138 #endif /* HB_KERN_HH */
139