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[kerx] Use GPOS attachment facilities for CrossStream kerning

This commit is contained in:
Behdad Esfahbod 2018-11-07 14:38:29 -05:00
parent e10a856eb2
commit b2f687c256
1 changed files with 35 additions and 16 deletions
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51
src/hb-aat-layout-kerx-table.hh
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@ -236,9 +236,7 @@ struct KerxSubTableFormat1
* other subtables in kerx. Discovered via testing. */
kernAction (&table->machine + table->kernAction),
depth (0),
crossStream (table->header.coverage & table->header.CrossStream),
crossOffset (0) {}
crossStream (table->header.coverage & table->header.CrossStream) {}
/* TODO
* 'kern' table has this pecularity, we don't currently implement.
@ -307,21 +305,25 @@ struct KerxSubTableFormat1
/* "The end of the list is marked by an odd value..." Ignore it. */
v &= ~1;
hb_glyph_position_t &o = buffer->pos[idx];
/* The following flag is undocumented in the spec, but described
* in the 'kern' table example. */
if (v == -0x8000)
{
crossOffset = 0;
v = 0;
o.attach_type() = ATTACH_TYPE_NONE;
o.attach_chain() = 0;
o.x_offset = o.y_offset = 0;
}
if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
else if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
{
if (crossStream)
{
crossOffset += v;
if (!buffer->pos[idx].y_offset)
buffer->pos[idx].y_offset += c->font->em_scale_y (crossOffset);
if (buffer->pos[idx].attach_type() && !buffer->pos[idx].y_offset)
{
o.y_offset = c->font->em_scale_y (v);
buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
}
}
else if (buffer->info[idx].mask & kern_mask)
{
@ -337,9 +339,11 @@ struct KerxSubTableFormat1
if (crossStream)
{
/* CoreText doesn't do crossStream kerning in vertical. We do. */
crossOffset += v;
if (!buffer->pos[idx].x_offset)
buffer->pos[idx].x_offset = c->font->em_scale_x (crossOffset);
if (buffer->pos[idx].attach_type() && !buffer->pos[idx].x_offset)
{
o.x_offset = c->font->em_scale_x (v);
buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
}
}
else if (buffer->info[idx].mask & kern_mask)
{
@ -353,8 +357,6 @@ struct KerxSubTableFormat1
}
depth = 0;
}
else
buffer->pos[buffer->idx].y_offset += c->font->em_scale_y (crossOffset);
return true;
}
@ -366,7 +368,6 @@ struct KerxSubTableFormat1
unsigned int stack[8];
unsigned int depth;
bool crossStream;
int crossOffset;
};
inline bool apply (hb_aat_apply_context_t *c) const
@ -875,6 +876,7 @@ struct KerxTable
{
typedef typename T::SubTable SubTable;
bool seenCrossStream = false;
c->set_lookup_index (0);
const SubTable *st = &thiz()->firstSubTable;
unsigned int count = thiz()->tableCount;
@ -894,6 +896,23 @@ struct KerxTable
if (!c->buffer->message (c->font, "start %c%c%c%c subtable %d", HB_UNTAG (thiz()->tableTag), c->lookup_index))
goto skip;
if (!seenCrossStream &&
(st->u.header.coverage & st->u.header.CrossStream))
{
/* Attach all glyphs into a chain. */
seenCrossStream = true;
hb_glyph_position_t *pos = c->buffer->pos;
unsigned int count = c->buffer->len;
for (unsigned int i = 0; i < count; i++)
{
pos[i].attach_type() = ATTACH_TYPE_CURSIVE;
pos[i].attach_chain() = HB_DIRECTION_IS_FORWARD (c->buffer->props.direction) ? -1 : +1;
/* We intentionally don't set HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT,
* since there needs to be a non-zero attachment for post-positioning to
* be needed. */
}
}
if (reverse)
c->buffer->reverse ();