title: OpacityMask not working with WPF WindowsFormsHost?
body: <p>I'm trying to put a rounded border on a control which is hosted through a WindowsFormHost object.  It seems like no matter what I set for OpacityMask, it has no effect on the rendering.  Is there something I've missed?</p>
  
  <p>Here is the XAML code I am using.  The child control is added at run-time.  I've tried various combinations of masks, none of which worked for me.  Any help would be appreciated.  Thanks!</p>
  
  <pre><code>    &lt;WindowsFormsHost Background="#FF2BBA62" Height="414" Width="516" Margin="176.5,223,309.5,92" Name="vcxHost1" UseLayoutRounding="False" ClipToBounds="True" &gt;
          &lt;WindowsFormsHost.OpacityMask&gt;
              &lt;VisualBrush&gt;
                  &lt;VisualBrush.Visual&gt;
                      &lt;Rectangle Height="10" Width="100" Name="border1" /&gt;
                  &lt;/VisualBrush.Visual&gt;
              &lt;/VisualBrush&gt;
          &lt;/WindowsFormsHost.OpacityMask&gt;
      &lt;/WindowsFormsHost&gt;
  </code></pre>