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Optimize fallback kerning 

Patch from Jonathan Kew.  "These changes seem to yield a small but
just-about-measurable improvement with old fonts that lack GPOS
kerning."
This commit is contained in:
Behdad Esfahbod 2013-10-27 21:04:55 +01:00
parent 133eeba6a3
commit 6b03e3c724
1 changed files with 29 additions and 18 deletions
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47
src/hb-ot-shape-fallback.cc
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@ -430,41 +430,52 @@ _hb_ot_shape_fallback_kern (const hb_ot_shape_plan_t *plan,
hb_font_t *font,
hb_buffer_t *buffer)
{
unsigned int count = buffer->len;
hb_mask_t kern_mask = plan->map.get_1_mask (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction) ?
HB_TAG ('k','e','r','n') : HB_TAG ('v','k','r','n'));
if (!kern_mask) return;
unsigned int count = buffer->len;
OT::hb_apply_context_t c (1, font, buffer);
c.set_lookup_mask (kern_mask);
c.set_lookup_props (OT::LookupFlag::IgnoreMarks);
for (buffer->idx = 0; buffer->idx < count;)
hb_glyph_info_t *info = buffer->info;
hb_glyph_position_t *pos = buffer->pos;
for (unsigned int idx = 0; idx < count;)
{
OT::hb_apply_context_t::skipping_forward_iterator_t skippy_iter (&c, buffer->idx, 1);
OT::hb_apply_context_t::skipping_forward_iterator_t skippy_iter (&c, idx, 1);
if (!skippy_iter.next ())
{
buffer->idx++;
idx++;
continue;
}
hb_position_t x_kern, y_kern, kern1, kern2;
font->get_glyph_kerning_for_direction (buffer->info[buffer->idx].codepoint,
buffer->info[skippy_iter.idx].codepoint,
hb_position_t x_kern, y_kern;
font->get_glyph_kerning_for_direction (info[idx].codepoint,
info[skippy_iter.idx].codepoint,
buffer->props.direction,
&x_kern, &y_kern);
kern1 = x_kern >> 1;
kern2 = x_kern - kern1;
buffer->pos[buffer->idx].x_advance += kern1;
buffer->pos[skippy_iter.idx].x_advance += kern2;
buffer->pos[skippy_iter.idx].x_offset += kern2;
if (x_kern)
{
hb_position_t kern1 = x_kern >> 1;
hb_position_t kern2 = x_kern - kern1;
pos[idx].x_advance += kern1;
pos[skippy_iter.idx].x_advance += kern2;
pos[skippy_iter.idx].x_offset += kern2;
}
kern1 = y_kern >> 1;
kern2 = y_kern - kern1;
buffer->pos[buffer->idx].y_advance += kern1;
buffer->pos[skippy_iter.idx].y_advance += kern2;
buffer->pos[skippy_iter.idx].y_offset += kern2;
if (y_kern)
{
hb_position_t kern1 = y_kern >> 1;
hb_position_t kern2 = y_kern - kern1;
pos[idx].y_advance += kern1;
pos[skippy_iter.idx].y_advance += kern2;
pos[skippy_iter.idx].y_offset += kern2;
}
buffer->idx = skippy_iter.idx;
idx = skippy_iter.idx;
}
}