From 52ebdff49d13f239efc886de935d47be9860f6e5 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 27 Sep 2011 12:38:16 -0400
Subject: [PATCH] Fix GSUB lookuptype 1 subtype 1 delta wrapping

---
 src/hb-ot-layout-gsub-table.hh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/hb-ot-layout-gsub-table.hh b/src/hb-ot-layout-gsub-table.hh
index 4f4c1719a..4c423cce1 100644
--- a/src/hb-ot-layout-gsub-table.hh
+++ b/src/hb-ot-layout-gsub-table.hh
@@ -47,7 +47,9 @@ struct SingleSubstFormat1
     if (likely (index == NOT_COVERED))
       return false;
 
-    glyph_id += deltaGlyphID;
+    /* According to the Adobe Annotated OpenType Suite, result is always
+     * limited to 16bit. */
+    glyph_id = (glyph_id + deltaGlyphID) & 0xFFFF;
     c->replace_glyph (glyph_id);
 
     return true;