code: func (v *Screen) GetSystemVisual() (*Visual, error) {
  	c := C.gdk_screen_get_system_visual(v.native())
  	if c == nil {
  		return nil, nilPtrErr
  	}
  
  	return &Visual{glib.Take(unsafe.Pointer(c))}, nil
  }
docs: // GetSystemVisual is a wrapper around gdk_screen_get_system_visual().