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.
Group leader window, or
NULLto restore the default group leader window.
The argument can be
The data is owned by the caller of the method.