From 4b8de1ea804b225e8357422d0686aad76b05ccf3 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Mon, 6 Jun 2016 23:08:54 -0700
Subject: [PATCH] Round, not truncate, when scaling values

Fixes https://github.com/behdad/harfbuzz/issues/255
---
 src/hb-font-private.hh | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/hb-font-private.hh b/src/hb-font-private.hh
index 8da40a992..0b7557794 100644
--- a/src/hb-font-private.hh
+++ b/src/hb-font-private.hh
@@ -505,7 +505,13 @@ struct hb_font_t {
   }
 
   private:
-  inline hb_position_t em_scale (int16_t v, int scale) { return (hb_position_t) (v * (int64_t) scale / face->get_upem ()); }
+  inline hb_position_t em_scale (int16_t v, int scale)
+  {
+    int upem = face->get_upem ();
+    int64_t scaled = v * (int64_t) scale;
+    scaled += scaled >= 0 ? upem/2 : -upem/2; /* Round. */
+    return (hb_position_t) (scaled / upem);
+  }
 };
 
 #define HB_SHAPER_DATA_CREATE_FUNC_EXTRA_ARGS