        {
                            type: 'select',
                            text: 'box layout:',
                            values: [
                                'do_nothing',
                                {
                                    left: 50, top: 80, right: '20%', bottom: 20,
                                },
                                {
                                    left: null, top: null, right: null, bottom: null,
                                },
                    