title: HitTest across Windows?
body: <p>Ok, so my <a href="https://stackoverflow.com/questions/3473016/how-to-sort-windows-by-z-index">previous question</a> did not produce any useful answers, so I'll try to come from a different direction.</p>
  
  <p>My application has, potentially, several windows. Given a point in screen coordinates, I need to find which window it "falls" onto - i.e. find the Window that is foremost of all windows containing said point.</p>
  
  <p>If they were <code>Visual</code>s inside one window, I would use <code>VisualTreeHelper.HitTest</code>. But since they are different windows, it's not clear what to give as the first argument to that method.</p>