/// <summary>
 /// A message handler for the Activate event of the parent window.
 /// Needed to refresh the child controls.
 /// </summary>
 /// <param name="sender">The source of the event.</param>
 /// <param name="e">An <see cref="EventArgs"/> that contains the event data.</param>
 private void ActivateParent(object sender, EventArgs e)
 {
     try
     {
         if (activeDoc != null)
         {
             activeDoc.SetFocus(true);
         }
     }
     catch (Exception ex)
     {
         Console.WriteLine("DockManager.ActivateParent: " + ex.Message);
     }
     finally
     {
         Invalidate(true);
     }
 }