title: Determine window visibility in Vista
body: <p>I want to determine if a certain window is visible to the user or hidden/occluded. In Windows XP I would use the GetClipBox() function and check for a NULLREGION or empty RECT return value. This worked perfectly fine, but on Windows Vista it does not work if another window is occluding the window. In this case, GetClipBox() is returning SIMPLEREGION with a non-empty RECT.</p>
  
  <p>Does anybody know why this is not working on Vista or if there is another way to check if a window can be seen by the user?</p>