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[trak] Implement extrapolation 

This concludes trak, as well as AAT shaping support!
This commit is contained in:
Behdad Esfahbod 2018-10-11 11:25:07 -04:00
parent d6a12dba6d
commit 04f72e8990
1 changed files with 20 additions and 19 deletions
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39
src/hb-aat-layout-trak-table.hh
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@ -82,6 +82,22 @@ struct TrackTableEntry
struct TrackData
{
inline float interpolate_at (unsigned int idx,
float target_size,
const TrackTableEntry &trackTableEntry,
const void *base) const
{
unsigned int sizes = nSizes;
hb_array_t<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 (float) t * trackTableEntry.get_value (base, idx + 1, sizes) +
((float) 1.0 - t) * trackTableEntry.get_value (base, idx, sizes);
return 0;
}
inline float get_tracking (const void *base, float ptem) const
{
/* CoreText points are CSS pixels (96 per inch),
@ -90,13 +106,10 @@ struct TrackData
* https://developer.apple.com/library/content/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/Explained/Explained.html
*/
float csspx = ptem * 96.f / 72.f;
Fixed fixed_size;
fixed_size.set_float (csspx);
/*
* Choose track.
*/
const TrackTableEntry *trackTableEntry = nullptr;
unsigned int count = nTracks;
for (unsigned int i = 0; i < count; i++)
@ -117,31 +130,19 @@ struct TrackData
/*
* Choose size.
*/
unsigned int sizes = nSizes;
if (!sizes) return 0.;
if (sizes == 1) return trackTableEntry->get_value (base, 0, sizes);
/* TODO bfind() */
unsigned int size_index;
hb_array_t<Fixed> size_table ((base+sizeTable).arrayZ, sizes);
unsigned int size_index;
for (size_index = 0; size_index < sizes; size_index++)
if ((int) size_table[size_index] >= (int) fixed_size)
if (size_table[size_index].to_float () >= csspx)
break;
// TODO(ebraminio): We don't attempt to extrapolate to larger or
// smaller values for now but we should do, per spec
if (size_index == sizes)
return trackTableEntry->get_value (base, sizes - 1, sizes);
if (size_index == 0 || size_table[size_index] == fixed_size)
return trackTableEntry->get_value (base, size_index, sizes);
float s0 = size_table[size_index - 1].to_float ();
float s1 = size_table[size_index].to_float ();
float t = (csspx - s0) / (s1 - s0);
return (float) t * trackTableEntry->get_value (base, size_index, sizes) +
((float) 1.0 - t) * trackTableEntry->get_value (base, size_index - 1, sizes);
return interpolate_at (size_index ? size_index - 1 : 0, csspx,
*trackTableEntry, base);
}
inline bool sanitize (hb_sanitize_context_t *c, const void *base) const