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Allow MultipleSubst to delete glyph 

Fixes https://github.com/behdad/harfbuzz/issues/253

Hopefully we got the logic right.
This commit is contained in:
Behdad Esfahbod 2016-05-06 16:19:19 +01:00
parent 3c1666cfb5
commit 359dead960
2 changed files with 14 additions and 14 deletions
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17
src/hb-ot-layout-gsub-table.hh
View File

@ -265,16 +265,6 @@ struct Sequence
TRACE_APPLY (this);
unsigned int count = substitute.len;
/* TODO:
* Testing shows that Uniscribe actually allows zero-len susbstitute,
* which essentially deletes a glyph. We don't allow for now. It
* can be confusing to the client since the cluster from the deleted
* glyph won't be merged with any output cluster... Also, currently
* buffer->move_to() makes assumptions about this too. Perhaps fix
* in the future after figuring out what to do with the clusters.
*/
if (unlikely (!count)) return_trace (false);
/* Special-case to make it in-place and not consider this
* as a "multiplied" substitution. */
if (unlikely (count == 1))
@ -282,6 +272,13 @@ struct Sequence
c->replace_glyph (substitute.array[0]);
return_trace (true);
}
/* Spec disallows this, but Uniscribe allows it.
* https://github.com/behdad/harfbuzz/issues/253 */
else if (unlikely (count == 0))
{
c->buffer->delete_glyph ();
return_trace (true);
}
unsigned int klass = _hb_glyph_info_is_ligature (&c->buffer->cur()) ?
HB_OT_LAYOUT_GLYPH_PROPS_BASE_GLYPH : 0;

11
src/hb-ot-layout-gsubgpos-private.hh
View File

@ -996,10 +996,13 @@ static inline bool apply_lookup (hb_apply_context_t *c,
/* Recursed lookup changed buffer len. Adjust. */
/* end can't go back past the current match position.
* Note: this is only true because we do NOT allow MultipleSubst
* with zero sequence len. */
end = MAX (MIN((int) match_positions[idx] + 1, (int) new_len), int (end) + delta);
end = int (end) + delta;
if (end <= match_positions[idx])
{
/* There can't be any further changes. */
assert (end == match_positions[idx]);
break;
}
unsigned int next = idx + 1; /* next now is the position after the recursed lookup. */