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src/hb-ot-shape.cc

diff --git a/src/hb-ot-shape.cc b/src/hb-ot-shape.cc
index 8b1863c..b4f30a5 100644
--- a/src/hb-ot-shape.cc
+++ b/src/hb-ot-shape.cc
@@ -30,6 +30,7 @@
 
 #include "hb-ot-layout.h"
 
+/* XXX vertical */
 hb_tag_t default_features[] = {
   /* GSUB */
   HB_TAG('c','c','m','p'),