void t_Elapsed(object sender, ElapsedEventArgs e)
 {
     try {
         MainWindow.inst().Dispatcher.Invoke(delegate()
         {
             bpMargin.InvalidateVisual();
         });
     }
     catch (Exception ex)
     {
         // Swallow the exception, it's probably just a shut down issue
     }
 }
 void t_Elapsed(object sender, ElapsedEventArgs e)
 {
     MainWindow.inst().Dispatcher.Invoke(delegate() {
         bpMargin.InvalidateVisual();
     });
 }