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