212 lines
6.4 KiB
C++
212 lines
6.4 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-private.hh"
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#include "hb-ot-layout-private.hh"
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#include "hb-open-type-private.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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inline bool sanitize (hb_sanitize_context_t *c, const void *base,
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unsigned int 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, size))));
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}
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private:
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inline float get_track_value () const
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{
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return track.to_float ();
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}
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inline int get_value (const void *base, unsigned int index) const
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{
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return (base+valuesZ)[index];
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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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OffsetTo<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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inline 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 (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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inline float 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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Fixed fixed_size;
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fixed_size.set_float (csspx);
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/* XXX Clean this up. Make it work with nSizes==1 and 0. */
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unsigned int sizes = nSizes;
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const TrackTableEntry *trackTableEntry = nullptr;
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for (unsigned int i = 0; i < sizes; ++i)
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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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trackTableEntry = &trackTable[0];
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// We couldn't match any, exit
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if (!trackTableEntry) return 0.;
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/* TODO bfind() */
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unsigned int size_index;
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UnsizedArrayOf<Fixed> size_table = base+sizeTable;
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for (size_index = 0; size_index < sizes; ++size_index)
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if (size_table[size_index] >= fixed_size)
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break;
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// TODO(ebraminio): We don't attempt to extrapolate to larger or
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// smaller values for now but we should do, per spec
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if (size_index == sizes)
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return trackTableEntry->get_value (base, sizes - 1);
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if (size_index == 0 || size_table[size_index] == fixed_size)
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return trackTableEntry->get_value (base, size_index);
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float s0 = size_table[size_index - 1].to_float ();
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float s1 = size_table[size_index].to_float ();
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float t = (csspx - s0) / (s1 - s0);
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return (float) t * trackTableEntry->get_value (base, size_index) +
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((float) 1.0 - t) * trackTableEntry->get_value (base, size_index - 1);
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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> >
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sizeTable; /* Offset to 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 const hb_tag_t tableTag = HB_AAT_TAG_trak;
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inline 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 (unlikely (c->check_struct (this) &&
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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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inline bool apply (hb_aat_apply_context_t *c) const
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{
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TRACE_APPLY (this);
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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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float tracking = trackData.get_tracking (this, ptem);
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hb_position_t advance_to_add = c->font->em_scalef_x (tracking / 2);
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foreach_grapheme (buffer, start, end)
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{
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buffer->pos[start].x_offset += advance_to_add;
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buffer->pos[start].x_advance += advance_to_add;
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buffer->pos[end].x_advance += advance_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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float tracking = trackData.get_tracking (this, ptem);
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hb_position_t advance_to_add = c->font->em_scalef_y (tracking / 2);
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foreach_grapheme (buffer, start, end)
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{
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buffer->pos[start].y_offset += advance_to_add;
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buffer->pos[start].y_advance += advance_to_add;
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buffer->pos[end].y_advance += advance_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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protected:
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FixedVersion<> version; /* Version of the tracking table--currently
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* 0x00010000u for version 1.0. */
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HBUINT16 format; /* Format of the tracking table */
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OffsetTo<TrackData> horizData; /* TrackData for horizontal text */
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OffsetTo<TrackData> vertData; /* TrackData for vertical text */
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HBUINT16 reserved; /* Reserved. Set to 0. */
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public:
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DEFINE_SIZE_MIN (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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