Function clutter_box_layout_pack 

pub unsafe extern "C" fn clutter_box_layout_pack(
    layout: *mut ClutterBoxLayout,
    actor: *mut ClutterActor,
    expand: gboolean,
    x_fill: gboolean,
    y_fill: gboolean,
    x_align: ClutterBoxAlignment,
    y_align: ClutterBoxAlignment,
)