    /**
     * A Column definition class which renders boolean data fields.  See the {@link Ext.grid.column.Column#xtype xtype}
     * config option of {@link Ext.grid.column.Column} for more details.
     *
     *     @example
     *     Ext.create('Ext.data.Store', {
     *        storeId:'sampleStore',
     *        fields:[
     *            {name: 'framework', type: 'string'},
     *            {name: 'rocks', type: 'boolean'}
     *        ],
     *        data:{'items':[
     *            { 'framework': "Ext JS 4",     'rocks': true  },
     *            { 'framework': "Sencha Touch", 'rocks': true  },
     *            { 'framework': "Ext GWT",      'rocks': true  },
     *            { 'framework': "Other Guys",   'rocks': false }
     *        ]},
     *        proxy: {
     *            type: 'memory',
     *            reader: {
     *                type: 'json',
     *                root: 'items'
     *            }
     *        }
     *     });
     *
     *     Ext.create('Ext.grid.Panel', {
     *         title: 'Boolean Column Demo',
     *         store: Ext.data.StoreManager.lookup('sampleStore'),
     *         columns: [
     *             { text: 'Framework',  dataIndex: 'framework', flex: 1 },
     *             {
     *                 xtype: 'booleancolumn',
     *                 text: 'Rocks',
     *                 trueText: 'Yes',
     *                 falseText: 'No',
     *                 dataIndex: 'rocks'
     *             }
     *         ],
     *         height: 200,
     *         width: 400,
     *         renderTo: Ext.getBody()
     *     });
     */
    Ext.define('Ext.grid.column.Boolean', {
        extend: 'Ext.grid.column.Column',
        alias: ['widget.booleancolumn'],
        alternateClassName: 'Ext.grid.BooleanColumn',

        /**
         * @cfg {String} trueText
         * The string returned by the renderer when the column value is not falsey.
         */
        trueText: 'true',

        /**
         * @cfg {String} falseText
         * The string returned by the renderer when the column value is falsey (but not undefined).
         */
        falseText: 'false',

        /**
         * @cfg {String} undefinedText
         * The string returned by the renderer when the column value is undefined.
         */
        undefinedText: '&#160;',

        constructor: function(cfg){
            this.callParent(arguments);
            var trueText      = this.trueText,
                falseText     = this.falseText,
                undefinedText = this.undefinedText;

            this.renderer = function(value){
                if(value === undefined){
                    return undefinedText;
                }
                if(!value || value === 'false'){
                    return falseText;
                }
                return trueText;
            };
        }
    });