Retrieves the focus chain of the container, if one has been set explicitly. If no focus chain has been explicitly set, GTK+ computes the focus chain based on the positions of the children. In that case, GTK+ stores NULL in focusable_widgets and returns FALSE.
location to store the focus chain of the container, or NULL. You should free this list using g_list_free() when you are done with it, however no additional reference count is added to the individual widgets in the focus chain.
TRUE if the focus chain of the container has been set explicitly.
Deprecated: For overriding focus behavior, use the GtkWidgetClass::focus signal.