Returns the window handle.
simple-pane-handle pane => handle
simple-pane-handle
=>
handle
A X windowid.
On Windows simple-pane-handle returns the hwnd of pane . On X11/Motif, it returns the windowid of the main part of pane .
Use this function with caution: in general, drawing and moving of CAPI windows should be done through the CAPI.