code: func (v *Box) SetChildPacking(child IWidget, expand, fill bool, padding uint, packType PackType) {
  	C.gtk_box_set_child_packing(v.native(), child.toWidget(), gbool(expand),
  		gbool(fill), C.guint(padding), C.GtkPackType(packType))
  }
docs: // SetChildPacking() is a wrapper around gtk_box_set_child_packing().