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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 
42 namespace AAT {
43 
44 
45 struct TrackTableEntry
46 {
47   friend struct TrackData;
48 
get_track_valueAAT::TrackTableEntry49   float get_track_value () const { return track.to_float (); }
50 
get_valueAAT::TrackTableEntry51   int get_value (const void *base, unsigned int index,
52 		 unsigned int table_size) const
53   { return (base+valuesZ).as_array (table_size)[index]; }
54 
55   public:
sanitizeAAT::TrackTableEntry56   bool sanitize (hb_sanitize_context_t *c, const void *base,
57 		 unsigned int table_size) const
58   {
59     TRACE_SANITIZE (this);
60     return_trace (likely (c->check_struct (this) &&
61 			  (valuesZ.sanitize (c, base, table_size))));
62   }
63 
64   protected:
65   Fixed		track;		/* Track value for this record. */
66   NameID	trackNameID;	/* The 'name' table index for this track.
67 				 * (a short word or phrase like "loose"
68 				 * or "very tight") */
69   OffsetTo<UnsizedArrayOf<FWORD>, HBUINT16, false>
70 		valuesZ;	/* Offset from start of tracking table to
71 				 * per-size tracking values for this track. */
72 
73   public:
74   DEFINE_SIZE_STATIC (8);
75 };
76 
77 struct TrackData
78 {
interpolate_atAAT::TrackData79   float interpolate_at (unsigned int idx,
80 			float target_size,
81 			const TrackTableEntry &trackTableEntry,
82 			const void *base) const
83   {
84     unsigned int sizes = nSizes;
85     hb_array_t<const Fixed> size_table ((base+sizeTable).arrayZ, sizes);
86 
87     float s0 = size_table[idx].to_float ();
88     float s1 = size_table[idx + 1].to_float ();
89     float t = unlikely (s0 == s1) ? 0.f : (target_size - s0) / (s1 - s0);
90     return t * trackTableEntry.get_value (base, idx + 1, sizes) +
91 	   (1.f - t) * trackTableEntry.get_value (base, idx, sizes);
92   }
93 
get_trackingAAT::TrackData94   int get_tracking (const void *base, float ptem) const
95   {
96     /* CoreText points are CSS pixels (96 per inch),
97      * NOT typographic points (72 per inch).
98      *
99      * https://developer.apple.com/library/content/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/Explained/Explained.html
100      */
101     float csspx = ptem * 96.f / 72.f;
102 
103     /*
104      * Choose track.
105      */
106     const TrackTableEntry *trackTableEntry = nullptr;
107     unsigned int count = nTracks;
108     for (unsigned int i = 0; i < count; i++)
109     {
110       /* Note: Seems like the track entries are sorted by values.  But the
111        * spec doesn't explicitly say that.  It just mentions it in the example. */
112 
113       /* For now we only seek for track entries with zero tracking value */
114 
115       if (trackTable[i].get_track_value () == 0.f)
116       {
117 	trackTableEntry = &trackTable[i];
118 	break;
119       }
120     }
121     if (!trackTableEntry) return 0.;
122 
123     /*
124      * Choose size.
125      */
126     unsigned int sizes = nSizes;
127     if (!sizes) return 0.;
128     if (sizes == 1) return trackTableEntry->get_value (base, 0, sizes);
129 
130     hb_array_t<const Fixed> size_table ((base+sizeTable).arrayZ, sizes);
131     unsigned int size_index;
132     for (size_index = 0; size_index < sizes - 1; size_index++)
133       if (size_table[size_index].to_float () >= csspx)
134         break;
135 
136     return round (interpolate_at (size_index ? size_index - 1 : 0, csspx,
137 				  *trackTableEntry, base));
138   }
139 
sanitizeAAT::TrackData140   bool sanitize (hb_sanitize_context_t *c, const void *base) const
141   {
142     TRACE_SANITIZE (this);
143     return_trace (likely (c->check_struct (this) &&
144 			  sizeTable.sanitize (c, base, nSizes) &&
145 			  trackTable.sanitize (c, nTracks, base, nSizes)));
146   }
147 
148   protected:
149   HBUINT16	nTracks;	/* Number of separate tracks included in this table. */
150   HBUINT16	nSizes;		/* Number of point sizes included in this table. */
151   LOffsetTo<UnsizedArrayOf<Fixed>, false>
152 		sizeTable;	/* Offset from start of the tracking table to
153 				 * Array[nSizes] of size values.. */
154   UnsizedArrayOf<TrackTableEntry>
155 		trackTable;	/* Array[nTracks] of TrackTableEntry records. */
156 
157   public:
158   DEFINE_SIZE_ARRAY (8, trackTable);
159 };
160 
161 struct trak
162 {
163   enum { tableTag = HB_AAT_TAG_trak };
164 
has_dataAAT::trak165   bool has_data () const { return version.to_int (); }
166 
applyAAT::trak167   bool apply (hb_aat_apply_context_t *c) const
168   {
169     TRACE_APPLY (this);
170 
171     hb_mask_t trak_mask = c->plan->trak_mask;
172 
173     const float ptem = c->font->ptem;
174     if (unlikely (ptem <= 0.f))
175       return_trace (false);
176 
177     hb_buffer_t *buffer = c->buffer;
178     if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
179     {
180       const TrackData &trackData = this+horizData;
181       int tracking = trackData.get_tracking (this, ptem);
182       hb_position_t offset_to_add = c->font->em_scalef_x (tracking / 2);
183       hb_position_t advance_to_add = c->font->em_scalef_x (tracking);
184       foreach_grapheme (buffer, start, end)
185       {
186         if (!(buffer->info[start].mask & trak_mask)) continue;
187 	buffer->pos[start].x_advance += advance_to_add;
188 	buffer->pos[start].x_offset += offset_to_add;
189       }
190     }
191     else
192     {
193       const TrackData &trackData = this+vertData;
194       int tracking = trackData.get_tracking (this, ptem);
195       hb_position_t offset_to_add = c->font->em_scalef_y (tracking / 2);
196       hb_position_t advance_to_add = c->font->em_scalef_y (tracking);
197       foreach_grapheme (buffer, start, end)
198       {
199         if (!(buffer->info[start].mask & trak_mask)) continue;
200 	buffer->pos[start].y_advance += advance_to_add;
201 	buffer->pos[start].y_offset += offset_to_add;
202       }
203     }
204 
205     return_trace (true);
206   }
207 
sanitizeAAT::trak208   bool sanitize (hb_sanitize_context_t *c) const
209   {
210     TRACE_SANITIZE (this);
211 
212     return_trace (likely (c->check_struct (this) &&
213 			  version.major == 1 &&
214 			  horizData.sanitize (c, this, this) &&
215 			  vertData.sanitize (c, this, this)));
216   }
217 
218   protected:
219   FixedVersion<>version;	/* Version of the tracking table
220 					 * (0x00010000u for version 1.0). */
221   HBUINT16	format; 	/* Format of the tracking table (set to 0). */
222   OffsetTo<TrackData>
223 		horizData;	/* Offset from start of tracking table to TrackData
224 				 * for horizontal text (or 0 if none). */
225   OffsetTo<TrackData>
226 		vertData;	/* Offset from start of tracking table to TrackData
227 				 * for vertical text (or 0 if none). */
228   HBUINT16	reserved;	/* Reserved. Set to 0. */
229 
230   public:
231   DEFINE_SIZE_STATIC (12);
232 };
233 
234 } /* namespace AAT */
235 
236 
237 #endif /* HB_AAT_LAYOUT_TRAK_TABLE_HH */
238