For most purposes this function is deprecated in favor of
gobject.object.ObjectWrap.setData. However, for historical reasons GTK+ stores
the #GtkWidget that owns a #GdkWindow as user data on the
#GdkWindow. So, custom widget implementations should use
this function for that. If GTK+ receives an event for a #GdkWindow,
and the user data for the window is non-null, GTK+ will assume the
user data is a #GtkWidget, and forward the event to that widget.
For most purposes this function is deprecated in favor of gobject.object.ObjectWrap.setData. However, for historical reasons GTK+ stores the #GtkWidget that owns a #GdkWindow as user data on the #GdkWindow. So, custom widget implementations should use this function for that. If GTK+ receives an event for a #GdkWindow, and the user data for the window is non-null, GTK+ will assume the user data is a #GtkWidget, and forward the event to that widget.