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))
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;
/* 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. */