gtk:application-window-by-id (application id)

application -- a gtk:application instance
id -- an unsigned integer identifier number

The gtk:application-window widget with ID id, or nil if there is no window with this ID.

Returns the application window with the given ID. The ID of an application window can be retrieved with the gtk:application-window-id function. Both gtk:window and gtk:application-window widgets can be added to an application, but only a gtk:application-window widget has an ID.