Accessor of the slot window of the gtk-widget class.
The generic function gtk-widget-window returns the widget's window of type gdk-window if it is realized, nil otherwise.
The generic function (setf gtk-widget-window) sets a widget's window.
This function should only be used in a widget's "realize" implementation. The window passed is usually either new window created with the function gdk-window-new, or the window of its parent widget as returned by the function gtk-widget-get-parent-window.
Widgets must indicate whether they will create their own gdk-window by calling the function gtk-widget-set-has-window. This is usually done in the widget's init() function.
This function does not add any reference to window.