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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   HBFixed	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   NNOffset16To<UnsizedArrayOf<FWORD>>
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 HBFixed> 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     /*
97      * Choose track.
98      */
99     const TrackTableEntry *trackTableEntry = nullptr;
100     unsigned int count = nTracks;
101     for (unsigned int i = 0; i < count; i++)
102     {
103       /* Note: Seems like the track entries are sorted by values.  But the
104        * spec doesn't explicitly say that.  It just mentions it in the example. */
105 
106       /* For now we only seek for track entries with zero tracking value */
107 
108       if (trackTable[i].get_track_value () == 0.f)
109       {
110 	trackTableEntry = &trackTable[i];
111 	break;
112       }
113     }
114     if (!trackTableEntry) return 0.;
115 
116     /*
117      * Choose size.
118      */
119     unsigned int sizes = nSizes;
120     if (!sizes) return 0.;
121     if (sizes == 1) return trackTableEntry->get_value (base, 0, sizes);
122 
123     hb_array_t<const HBFixed> size_table ((base+sizeTable).arrayZ, sizes);
124     unsigned int size_index;
125     for (size_index = 0; size_index < sizes - 1; size_index++)
126       if (size_table[size_index].to_float () >= ptem)
127 	break;
128 
129     return roundf (interpolate_at (size_index ? size_index - 1 : 0, ptem,
130 				   *trackTableEntry, base));
131   }
132 
sanitizeAAT::TrackData133   bool sanitize (hb_sanitize_context_t *c, const void *base) const
134   {
135     TRACE_SANITIZE (this);
136     return_trace (likely (c->check_struct (this) &&
137 			  sizeTable.sanitize (c, base, nSizes) &&
138 			  trackTable.sanitize (c, nTracks, base, nSizes)));
139   }
140 
141   protected:
142   HBUINT16	nTracks;	/* Number of separate tracks included in this table. */
143   HBUINT16	nSizes;		/* Number of point sizes included in this table. */
144   NNOffset32To<UnsizedArrayOf<HBFixed>>
145 		sizeTable;	/* Offset from start of the tracking table to
146 				 * Array[nSizes] of size values.. */
147   UnsizedArrayOf<TrackTableEntry>
148 		trackTable;	/* Array[nTracks] of TrackTableEntry records. */
149 
150   public:
151   DEFINE_SIZE_ARRAY (8, trackTable);
152 };
153 
154 struct trak
155 {
156   static constexpr hb_tag_t tableTag = HB_AAT_TAG_trak;
157 
has_dataAAT::trak158   bool has_data () const { return version.to_int (); }
159 
applyAAT::trak160   bool apply (hb_aat_apply_context_t *c) const
161   {
162     TRACE_APPLY (this);
163 
164     hb_mask_t trak_mask = c->plan->trak_mask;
165 
166     const float ptem = c->font->ptem;
167     if (unlikely (ptem <= 0.f))
168       return_trace (false);
169 
170     hb_buffer_t *buffer = c->buffer;
171     if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
172     {
173       const TrackData &trackData = this+horizData;
174       int tracking = trackData.get_tracking (this, ptem);
175       hb_position_t offset_to_add = c->font->em_scalef_x (tracking / 2);
176       hb_position_t advance_to_add = c->font->em_scalef_x (tracking);
177       foreach_grapheme (buffer, start, end)
178       {
179 	if (!(buffer->info[start].mask & trak_mask)) continue;
180 	buffer->pos[start].x_advance += advance_to_add;
181 	buffer->pos[start].x_offset += offset_to_add;
182       }
183     }
184     else
185     {
186       const TrackData &trackData = this+vertData;
187       int tracking = trackData.get_tracking (this, ptem);
188       hb_position_t offset_to_add = c->font->em_scalef_y (tracking / 2);
189       hb_position_t advance_to_add = c->font->em_scalef_y (tracking);
190       foreach_grapheme (buffer, start, end)
191       {
192 	if (!(buffer->info[start].mask & trak_mask)) continue;
193 	buffer->pos[start].y_advance += advance_to_add;
194 	buffer->pos[start].y_offset += offset_to_add;
195       }
196     }
197 
198     return_trace (true);
199   }
200 
sanitizeAAT::trak201   bool sanitize (hb_sanitize_context_t *c) const
202   {
203     TRACE_SANITIZE (this);
204 
205     return_trace (likely (c->check_struct (this) &&
206 			  version.major == 1 &&
207 			  horizData.sanitize (c, this, this) &&
208 			  vertData.sanitize (c, this, this)));
209   }
210 
211   protected:
212   FixedVersion<>version;	/* Version of the tracking table
213 				 * (0x00010000u for version 1.0). */
214   HBUINT16	format;		/* Format of the tracking table (set to 0). */
215   Offset16To<TrackData>
216 		horizData;	/* Offset from start of tracking table to TrackData
217 				 * for horizontal text (or 0 if none). */
218   Offset16To<TrackData>
219 		vertData;	/* Offset from start of tracking table to TrackData
220 				 * for vertical text (or 0 if none). */
221   HBUINT16	reserved;	/* Reserved. Set to 0. */
222 
223   public:
224   DEFINE_SIZE_STATIC (12);
225 };
226 
227 } /* namespace AAT */
228 
229 
230 #endif /* HB_AAT_LAYOUT_TRAK_TABLE_HH */
231