public VideoKeyframesWindow GetThumbsWindow()
 {
     if (_videoKeyframesWindow == null)
     {
         _videoKeyframesWindow                    = _videoThumbsWindowCreator();
         _videoKeyframesWindow.FormClosed        += new FormClosedEventHandler(ThumbsFormClosed);
         _videoKeyframesWindow.KeyframeSourceTree = _headerTree;
     }
     return(_videoKeyframesWindow);
 }
 private void ThumbsFormClosed(object sender, FormClosedEventArgs e)
 {
     _videoKeyframesWindow.FormClosed -= new FormClosedEventHandler(ThumbsFormClosed);
     _videoKeyframesWindow             = null;
 }