gtk:application-remove-window (application window)

application -- a gtk:application instance
window -- a gtk:window widget

Remove a window from the application. If the window argument belongs to the given application then this call is equivalent to setting the application property of window to nil, that is:

(gtk:application-remove-window application window)
== (setf (gtk:window-application window) nil)  

The application may stop running as a result of a call to this function, if the window argument was the last window of the application.