Round when scaling values

Doesn't matter for most users since they should be working in a
fixed sub-pixel scale anyway (ie. 22.10, 26.6, 16.16, etc).

TODO

@@ -12,8 +12,6 @@ General fixes:
 - Warn at compile time (and runtime with HB_DEBUG?) if no Unicode / font
   funcs found / set.
 
-- Do proper rounding when scaling from font space?  May be a non-issue.
-
 - Misc features:
   * init/medi/fina/isol for non-cursive scripts
 

src/hb-font-private.hh

@@ -461,7 +461,11 @@ struct hb_font_t {
   }
 
   private:
-  inline hb_position_t em_scale (int16_t v, int scale) { return v * (int64_t) scale / face->get_upem (); }
+  inline hb_position_t em_scale (int16_t v, int scale)
+  {
+    unsigned int upem = face->get_upem ();
+    return (v * (int64_t) scale + upem / 2) / upem;
+  }
 };
 
 #define HB_SHAPER_DATA_CREATE_FUNC_EXTRA_ARGS