This is a bolean control, not tristate.

diff --git a/modules/gui/qt4/ui/sprefs_video.ui b/modules/gui/qt4/ui/sprefs_video.ui
index bcb785368bb221c99f64a8fb62e245d61c0fecc6..67033b1364ce15faae974e63048dc8999ceae656 100644 (file)
--- a/modules/gui/qt4/ui/sprefs_video.ui
+++ b/modules/gui/qt4/ui/sprefs_video.ui
@@ -50,9 +50,6 @@
         <property name="checked" >
          <bool>true</bool>
         </property>
-        <property name="tristate" >
-         <bool>true</bool>
-        </property>
        </widget>
       </item>
       <item row="0" column="0" colspan="2" >