title: How to detect if user clicks on window title bar or any other part of window border in Java
body: <p>I have implemented a pop-up numeric keypad using the Swing Popup class. I have a button associated with a JTextField that opens the numeric keypad when the user clicks on it, and then when/if the JTextField loses focus the Popup closes. It generally works well, except that occasionally I get artifacts that are "left over" from a Popup after it has been hidden. Sometimes the artifact is an image of the Components that were shown in the Popup, but more often it is a "black hole" of sorts that obscures anything else displayed in the same area of the screen in which the Popup had been, which can only be remedied by shutting down the application and the JVM.</p>
  
  <p>The problem is difficult to reproduce, but it seems to manifest when the user manipulates the base Window while the Popup is open, such as by moving or resizing it. My thought is to simply hide the Popup when anything like that happens, which I can do with a combination of a WindowListener and a ComponentListener. However, I'd like to take it one step further and hide the Popup as soon as the user so much as clicks on the window title bar or another portion of its frame, even before they move, resize or iconify it. JComboBox popups in fact work this way. However, I have been unable to find any kind of mechanism by which I can be notified that a user has clicked on the window title bar. I've looked at the JComboBox and related code and can't figure out from that how it's working this magic, either. Is there any other kind of listener I could use to get this kind of notification?</p>