code: public VisDialog show (Stage stage) {
  		show(stage, sequence(Actions.alpha(0), Actions.fadeIn(0.4f, Interpolation.fade)));
  		setPosition(Math.round((stage.getWidth() - getWidth()) / 2), Math.round((stage.getHeight() - getHeight()) / 2));
  		return this;
  	}
docs: {@link #pack() Packs} the dialog and adds it to the stage, centered with default fadeIn action