code: func ScrollbarNew(orientation Orientation, adjustment *Adjustment) (*Scrollbar, error) {
  	c := C.gtk_scrollbar_new(C.GtkOrientation(orientation), adjustment.native())
  	if c == nil {
  		return nil, nilPtrErr
  	}
  	return wrapScrollbar(glib.Take(unsafe.Pointer(c))), nil
  }
docs: // ScrollbarNew is a wrapper around gtk_scrollbar_new().