[GPOS] Fix mark-to-mark positioning when one of the marks is a ligature
This commit: a3313e54008167e415b72c780ca7b9cda958d07e broke MarkMarkPos
when one of the marks itself is a ligature. That regressed 26 Tibetan
tests (up from zero!). Fix that. Tibetan back to zero.
diff --git a/src/hb-ot-layout-gpos-table.hh b/src/hb-ot-layout-gpos-table.hh
index 3b1ae2ab..83252c1 100644
--- a/src/hb-ot-layout-gpos-table.hh
+++ b/src/hb-ot-layout-gpos-table.hh
@@ -1263,14 +1263,27 @@
unsigned int j = skippy_iter.idx;
- /* Two marks match only if they belong to the same base, or same component
- * of the same ligature. That is, the lig_id numbers must match, and
- * if those are non-zero, the lig_comp number should also match. */
- if ((get_lig_id (c->buffer->info[j]) != get_lig_id (c->buffer->cur())) ||
- (get_lig_id (c->buffer->info[j]) > 0 &&
- get_lig_comp (c->buffer->info[j]) != get_lig_comp (c->buffer->cur())))
- return TRACE_RETURN (false);
+ unsigned int id1 = get_lig_id (c->buffer->cur());
+ unsigned int id2 = get_lig_id (c->buffer->info[j]);
+ unsigned int comp1 = get_lig_comp (c->buffer->cur());
+ unsigned int comp2 = get_lig_comp (c->buffer->info[j]);
+ if (likely (id1 == id2)) {
+ if (id1 == 0) /* Marks belonging to the same base. */
+ goto good;
+ else if (comp1 == comp2) /* Marks belonging to the same ligature component. */
+ goto good;
+ } else {
+ /* If ligature ids don't match, it may be the case that one of the marks
+ * itself is a ligature. In which case match. */
+ if ((id1 > 0 && !comp1) || (id2 > 0 && !comp2))
+ goto good;
+ }
+
+ /* Didn't match. */
+ return TRACE_RETURN (false);
+
+ good:
unsigned int mark2_index = (this+mark2Coverage) (c->buffer->info[j].codepoint);
if (mark2_index == NOT_COVERED) return TRACE_RETURN (false);
