gdk:window-group (window)

window -- a toplevel gdk:window object
leader -- a group leader gdk:window object, or nil to restore the default group leader window

The group leader window for window. The gdk:window-group function returns the group leader window for window. The (setf gdk:window-group) function sets the group leader window for window.

By default, GDK sets the group leader for all toplevel windows to a global window implicitly created by GDK. With this function you can override this default.

The group leader window allows the window manager to distinguish all windows that belong to a single application. It may for example allow users to minimize/unminimize all windows belonging to an application at once. You should only set a non-default group window if your application pretends to be multiple applications.