code: func (v *Window) GetDefaultWidget() *Widget {
  	c := C.gtk_window_get_default_widget(v.native())
  	if c == nil {
  		return nil
  	}
  	obj := glib.Take(unsafe.Pointer(c))
  	return wrapWidget(obj)
  }
docs: // GetDefaultWidget is a wrapper around gtk_window_get_default_widget().