Diff of /src/qtgui/preview_w.h [0ebfc4] .. [b2a0e6]

  Switch to side-by-side view 

--- a/src/qtgui/preview_w.h
+++ b/src/qtgui/preview_w.h
@@ -25,6 +25,7 @@
 
 #include <stdio.h>
 
+#include <QComboBox>
 #include <qvariant.h>
 #include <qwidget.h>