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     if (!buffer->message (font, "start kern"))
53       return;
54 
55     buffer->unsafe_to_concat ();
56     OT::hb_ot_apply_context_t c (1, font, buffer);
57     c.set_lookup_mask (kern_mask);
58     c.set_lookup_props (OT::LookupFlag::IgnoreMarks);
59     auto &skippy_iter = c.iter_input;
60 
61     bool horizontal = HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction);
62     unsigned int count = buffer->len;
63     hb_glyph_info_t *info = buffer->info;
64     hb_glyph_position_t *pos = buffer->pos;
65     for (unsigned int idx = 0; idx < count;)
66     {
67       if (!(info[idx].mask & kern_mask))
68       {
69 	idx++;
70 	continue;
71       }
72 
73       skippy_iter.reset (idx, 1);
74       unsigned unsafe_to;
75       if (!skippy_iter.next (&unsafe_to))
76       {
77 	idx++;
78 	continue;
79       }
80 
81       unsigned int i = idx;
82       unsigned int j = skippy_iter.idx;
83 
84       hb_position_t kern = driver.get_kerning (info[i].codepoint,
85 					       info[j].codepoint);
86 
87 
88       if (likely (!kern))
89 	goto skip;
90 
91       if (horizontal)
92       {
93 	if (scale)
94 	  kern = font->em_scale_x (kern);
95 	if (crossStream)
96 	{
97 	  pos[j].y_offset = kern;
98 	  buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
99 	}
100 	else
101 	{
102 	  hb_position_t kern1 = kern >> 1;
103 	  hb_position_t kern2 = kern - kern1;
104 	  pos[i].x_advance += kern1;
105 	  pos[j].x_advance += kern2;
106 	  pos[j].x_offset += kern2;
107 	}
108       }
109       else
110       {
111 	if (scale)
112 	  kern = font->em_scale_y (kern);
113 	if (crossStream)
114 	{
115 	  pos[j].x_offset = kern;
116 	  buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
117 	}
118 	else
119 	{
120 	  hb_position_t kern1 = kern >> 1;
121 	  hb_position_t kern2 = kern - kern1;
122 	  pos[i].y_advance += kern1;
123 	  pos[j].y_advance += kern2;
124 	  pos[j].y_offset += kern2;
125 	}
126       }
127 
128       buffer->unsafe_to_break (i, j + 1);
129 
130     skip:
131       idx = skippy_iter.idx;
132     }
133 
134     (void) buffer->message (font, "end kern");
135   }
136 
137   const Driver &driver;
138   bool crossStream;
139 };
140 
141 
142 } /* namespace OT */
143 
144 
145 #endif /* HB_KERN_HH */
146