238 lines
7.2 KiB
C++
238 lines
7.2 KiB
C++
/*
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* Copyright © 2018 Ebrahim Byagowi
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* Copyright © 2018 Google, Inc.
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*
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* This is part of HarfBuzz, a text shaping library.
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*
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* Permission is hereby granted, without written agreement and without
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* license or royalty fees, to use, copy, modify, and distribute this
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* software and its documentation for any purpose, provided that the
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* above copyright notice and the following two paragraphs appear in
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* all copies of this software.
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*
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* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
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* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
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* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*
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* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
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* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
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* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*
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* Google Author(s): Behdad Esfahbod
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*/
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#ifndef HB_AAT_LAYOUT_TRAK_TABLE_HH
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#define HB_AAT_LAYOUT_TRAK_TABLE_HH
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#include "hb-aat-layout-common.hh"
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#include "hb-ot-layout.hh"
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#include "hb-open-type.hh"
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/*
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* trak -- Tracking
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* https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6trak.html
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*/
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#define HB_AAT_TAG_trak HB_TAG('t','r','a','k')
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namespace AAT {
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struct TrackTableEntry
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{
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friend struct TrackData;
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float get_track_value () const { return track.to_float (); }
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int get_value (const void *base, unsigned int index,
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unsigned int table_size) const
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{ return (base+valuesZ).as_array (table_size)[index]; }
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public:
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bool sanitize (hb_sanitize_context_t *c, const void *base,
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unsigned int table_size) const
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{
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TRACE_SANITIZE (this);
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return_trace (likely (c->check_struct (this) &&
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(valuesZ.sanitize (c, base, table_size))));
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}
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protected:
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Fixed track; /* Track value for this record. */
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NameID trackNameID; /* The 'name' table index for this track.
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* (a short word or phrase like "loose"
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* or "very tight") */
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NNOffsetTo<UnsizedArrayOf<FWORD> >
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valuesZ; /* Offset from start of tracking table to
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* per-size tracking values for this track. */
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public:
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DEFINE_SIZE_STATIC (8);
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};
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struct TrackData
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{
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float interpolate_at (unsigned int idx,
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float target_size,
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const TrackTableEntry &trackTableEntry,
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const void *base) const
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{
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unsigned int sizes = nSizes;
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hb_array_t<const Fixed> size_table ((base+sizeTable).arrayZ, sizes);
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float s0 = size_table[idx].to_float ();
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float s1 = size_table[idx + 1].to_float ();
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float t = unlikely (s0 == s1) ? 0.f : (target_size - s0) / (s1 - s0);
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return t * trackTableEntry.get_value (base, idx + 1, sizes) +
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(1.f - t) * trackTableEntry.get_value (base, idx, sizes);
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}
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int get_tracking (const void *base, float ptem) const
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{
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/* CoreText points are CSS pixels (96 per inch),
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* NOT typographic points (72 per inch).
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*
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* https://developer.apple.com/library/content/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/Explained/Explained.html
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*/
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float csspx = ptem * 96.f / 72.f;
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/*
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* Choose track.
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*/
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const TrackTableEntry *trackTableEntry = nullptr;
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unsigned int count = nTracks;
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for (unsigned int i = 0; i < count; i++)
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{
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/* Note: Seems like the track entries are sorted by values. But the
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* spec doesn't explicitly say that. It just mentions it in the example. */
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/* For now we only seek for track entries with zero tracking value */
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if (trackTable[i].get_track_value () == 0.f)
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{
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trackTableEntry = &trackTable[i];
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break;
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}
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}
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if (!trackTableEntry) return 0.;
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/*
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* Choose size.
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*/
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unsigned int sizes = nSizes;
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if (!sizes) return 0.;
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if (sizes == 1) return trackTableEntry->get_value (base, 0, sizes);
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hb_array_t<const Fixed> size_table ((base+sizeTable).arrayZ, sizes);
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unsigned int size_index;
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for (size_index = 0; size_index < sizes - 1; size_index++)
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if (size_table[size_index].to_float () >= csspx)
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break;
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return round (interpolate_at (size_index ? size_index - 1 : 0, csspx,
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*trackTableEntry, base));
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}
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bool sanitize (hb_sanitize_context_t *c, const void *base) const
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{
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TRACE_SANITIZE (this);
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return_trace (likely (c->check_struct (this) &&
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sizeTable.sanitize (c, base, nSizes) &&
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trackTable.sanitize (c, nTracks, base, nSizes)));
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}
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protected:
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HBUINT16 nTracks; /* Number of separate tracks included in this table. */
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HBUINT16 nSizes; /* Number of point sizes included in this table. */
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LOffsetTo<UnsizedArrayOf<Fixed>, false>
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sizeTable; /* Offset from start of the tracking table to
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* Array[nSizes] of size values.. */
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UnsizedArrayOf<TrackTableEntry>
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trackTable; /* Array[nTracks] of TrackTableEntry records. */
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public:
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DEFINE_SIZE_ARRAY (8, trackTable);
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};
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struct trak
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{
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static constexpr hb_tag_t tableTag = HB_AAT_TAG_trak;
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bool has_data () const { return version.to_int (); }
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bool apply (hb_aat_apply_context_t *c) const
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{
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TRACE_APPLY (this);
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hb_mask_t trak_mask = c->plan->trak_mask;
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const float ptem = c->font->ptem;
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if (unlikely (ptem <= 0.f))
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return_trace (false);
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hb_buffer_t *buffer = c->buffer;
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if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
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{
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const TrackData &trackData = this+horizData;
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int tracking = trackData.get_tracking (this, ptem);
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hb_position_t offset_to_add = c->font->em_scalef_x (tracking / 2);
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hb_position_t advance_to_add = c->font->em_scalef_x (tracking);
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foreach_grapheme (buffer, start, end)
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{
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if (!(buffer->info[start].mask & trak_mask)) continue;
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buffer->pos[start].x_advance += advance_to_add;
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buffer->pos[start].x_offset += offset_to_add;
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}
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}
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else
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{
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const TrackData &trackData = this+vertData;
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int tracking = trackData.get_tracking (this, ptem);
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hb_position_t offset_to_add = c->font->em_scalef_y (tracking / 2);
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hb_position_t advance_to_add = c->font->em_scalef_y (tracking);
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foreach_grapheme (buffer, start, end)
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{
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if (!(buffer->info[start].mask & trak_mask)) continue;
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buffer->pos[start].y_advance += advance_to_add;
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buffer->pos[start].y_offset += offset_to_add;
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}
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}
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return_trace (true);
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}
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bool sanitize (hb_sanitize_context_t *c) const
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{
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TRACE_SANITIZE (this);
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return_trace (likely (c->check_struct (this) &&
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version.major == 1 &&
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horizData.sanitize (c, this, this) &&
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vertData.sanitize (c, this, this)));
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}
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protected:
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FixedVersion<>version; /* Version of the tracking table
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* (0x00010000u for version 1.0). */
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HBUINT16 format; /* Format of the tracking table (set to 0). */
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OffsetTo<TrackData>
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horizData; /* Offset from start of tracking table to TrackData
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* for horizontal text (or 0 if none). */
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OffsetTo<TrackData>
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vertData; /* Offset from start of tracking table to TrackData
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* for vertical text (or 0 if none). */
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HBUINT16 reserved; /* Reserved. Set to 0. */
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public:
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DEFINE_SIZE_STATIC (12);
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};
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} /* namespace AAT */
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#endif /* HB_AAT_LAYOUT_TRAK_TABLE_HH */
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