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
42namespace AAT {
43
44
45struct TrackTableEntry
46{
47 friend struct TrackData;
48
49 inline bool sanitize (hb_sanitize_context_t *c, const void *base,
50 unsigned int size) const
51 {
52 TRACE_SANITIZE (this);
53 return_trace (likely (c->check_struct (this) &&
54 (valuesZ.sanitize (c, base, size))));
55 }
56
57 private:
58 inline float get_track_value () const
59 {
60 return track.to_float ();
61 }
62
63 inline int get_value (const void *base, unsigned int index) const
64 {
65 return (base+valuesZ)[index];
66 }
67
68 protected:
69 Fixed track; /* Track value for this record. */
70 NameID trackNameID; /* The 'name' table index for this track */
71 OffsetTo<UnsizedArrayOf<FWORD> >
72 valuesZ; /* Offset from start of tracking table to
73 * per-size tracking values for this track. */
74
75 public:
76 DEFINE_SIZE_STATIC (8);
77};
78
79struct TrackData
80{
81 inline bool sanitize (hb_sanitize_context_t *c, const void *base) const
82 {
83 TRACE_SANITIZE (this);
84 return_trace (c->check_struct (this) &&
85 sizeTable.sanitize (c, base, nSizes) &&
86 trackTable.sanitize (c, nTracks, base, nSizes));
87 }
88
89 inline float get_tracking (const void *base, float ptem) const
90 {
91 /* CoreText points are CSS pixels (96 per inch),
92 * NOT typographic points (72 per inch).
93 *
94 * https://developer.apple.com/library/content/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/Explained/Explained.html
95 */
96 float csspx = ptem * 96.f / 72.f;
97 Fixed fixed_size;
98 fixed_size.set_float (csspx);
99
100 /* XXX Clean this up. Make it work with nSizes==1 and 0. */
101
102 unsigned int sizes = nSizes;
103
104 const TrackTableEntry *trackTableEntry = nullptr;
105 for (unsigned int i = 0; i < sizes; ++i)
106 // For now we only seek for track entries with zero tracking value
107 if (trackTable[i].get_track_value () == 0.f)
108 trackTableEntry = &trackTable[0];
109
110 // We couldn't match any, exit
111 if (!trackTableEntry) return 0.;
112
113 /* TODO bfind() */
114 unsigned int size_index;
115 UnsizedArrayOf<Fixed> size_table = base+sizeTable;
116 for (size_index = 0; size_index < sizes; ++size_index)
117 if (size_table[size_index] >= fixed_size)
118 break;
119
120 // TODO(ebraminio): We don't attempt to extrapolate to larger or
121 // smaller values for now but we should do, per spec
122 if (size_index == sizes)
123 return trackTableEntry->get_value (base, sizes - 1);
124 if (size_index == 0 || size_table[size_index] == fixed_size)
125 return trackTableEntry->get_value (base, size_index);
126
127 float s0 = size_table[size_index - 1].to_float ();
128 float s1 = size_table[size_index].to_float ();
129 float t = (csspx - s0) / (s1 - s0);
130 return (float) t * trackTableEntry->get_value (base, size_index) +
131 ((float) 1.0 - t) * trackTableEntry->get_value (base, size_index - 1);
132 }
133
134 protected:
135 HBUINT16 nTracks; /* Number of separate tracks included in this table. */
136 HBUINT16 nSizes; /* Number of point sizes included in this table. */
137 LOffsetTo<UnsizedArrayOf<Fixed> >
138 sizeTable; /* Offset to array[nSizes] of size values. */
139 UnsizedArrayOf<TrackTableEntry>
140 trackTable; /* Array[nTracks] of TrackTableEntry records. */
141
142 public:
143 DEFINE_SIZE_ARRAY (8, trackTable);
144};
145
146struct trak
147{
148 static const hb_tag_t tableTag = HB_AAT_TAG_trak;
149
150 inline bool sanitize (hb_sanitize_context_t *c) const
151 {
152 TRACE_SANITIZE (this);
153
154 return_trace (unlikely (c->check_struct (this) &&
155 horizData.sanitize (c, this, this) &&
156 vertData.sanitize (c, this, this)));
157 }
158
159 inline bool apply (hb_aat_apply_context_t *c) const
160 {
161 TRACE_APPLY (this);
162
163 const float ptem = c->font->ptem;
164 if (unlikely (ptem <= 0.f))
165 return_trace (false);
166
167 hb_buffer_t *buffer = c->buffer;
168 if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
169 {
170 const TrackData &trackData = this+horizData;
171 float tracking = trackData.get_tracking (this, ptem);
172 hb_position_t advance_to_add = c->font->em_scalef_x (tracking / 2);
173 foreach_grapheme (buffer, start, end)
174 {
175 buffer->pos[start].x_offset += advance_to_add;
176 buffer->pos[start].x_advance += advance_to_add;
177 buffer->pos[end].x_advance += advance_to_add;
178 }
179 }
180 else
181 {
182 const TrackData &trackData = this+vertData;
183 float tracking = trackData.get_tracking (this, ptem);
184 hb_position_t advance_to_add = c->font->em_scalef_y (tracking / 2);
185 foreach_grapheme (buffer, start, end)
186 {
187 buffer->pos[start].y_offset += advance_to_add;
188 buffer->pos[start].y_advance += advance_to_add;
189 buffer->pos[end].y_advance += advance_to_add;
190 }
191 }
192
193 return_trace (true);
194 }
195
196 protected:
197 FixedVersion<> version; /* Version of the tracking table--currently
198 * 0x00010000u for version 1.0. */
199 HBUINT16 format; /* Format of the tracking table */
200 OffsetTo<TrackData> horizData; /* TrackData for horizontal text */
201 OffsetTo<TrackData> vertData; /* TrackData for vertical text */
202 HBUINT16 reserved; /* Reserved. Set to 0. */
203
204 public:
205 DEFINE_SIZE_MIN (12);
206};
207
208} /* namespace AAT */
209
210
211#endif /* HB_AAT_LAYOUT_TRAK_TABLE_HH */
212