void background() throws ScriptException {
		if (statementLength < 2 || statementLength > 3)
			badArgumentCount();
		int tok = statement[1].tok;
		if (tok == Token.colorRGB || tok == Token.none)
			viewer.setBackgroundArgb(getArgbOrNoneParam(1));
		else viewer.setShapePropertyArgb(getShapeType(tok), "bgcolor", getArgbOrNoneParam(2));
	}