title: How do you specify or read the position of the main app window with guizero?
body: <p>I need to specify, or just read, the position (x and y coordinates of the top left corner) of the main app window in guizero.
  Apparently the App object does not have x and y positions properties that I can set or read.
  I found on this forum a solution for this issue with TkInter but not guizero.</p>
  
  <p>My goal is actually to be able to tell the mouse position within the app window. I can tell the mouse position with respect of the entire screen with the event data <strong>display_x</strong> and <strong>display_y</strong> and those change if I move the window around but I could use these values if I could account for the position of the window on the screen so, how do I find that out?</p>
  
  <p>The event data x and y, which are meant precisely to return the relative x and y position of the mouse within a widget, will NOT work IF that particular region of the window is "covered" by a widget like a text or a button.</p>
  
  <p>I am using Windows 10 and Python 3</p>
  
  <p>event_data.display_x = x position of the mouse on the entire display</p>
  
  <p>event_data.x = x position of the mouse on a widget. 
  Cannot use for the app window if that position is "covered" by a widget</p>