    /**
     * A Header subclass which renders a checkbox in each column cell which toggles the truthiness of the associated data field on click.
     *
     * Example usage:
     *
     *    // create the grid
     *    var grid = Ext.create('Ext.grid.Panel', {
     *        ...
     *        columns: [{
     *           text: 'Foo',
     *           ...
     *        },{
     *           xtype: 'checkcolumn',
     *           text: 'Indoor?',
     *           dataIndex: 'indoor',
     *           width: 55
     *        }]
     *        ...
     *    });
     *
     * In addition to toggling a Boolean value within the record data, this
     * class adds or removes a css class <tt>'x-grid-checked'</tt> on the td
     * based on whether or not it is checked to alter the background image used
     * for a column.
     */
    Ext.define('Ext.ux.CheckColumn', {
        extend: 'Ext.grid.column.Column',
        alias: 'widget.checkcolumn',

        /**
         * @cfg {Boolean} [stopSelection=true]
         * Prevent grid selection upon mousedown.
         */
        stopSelection: true,

        tdCls: Ext.baseCSSPrefix + 'grid-cell-checkcolumn',

        constructor: function() {
            this.addEvents(
                /**
                 * @event beforecheckchange
                 * Fires when before checked state of a row changes.
                 * The change may be vetoed by returning `false` from a listener.
                 * @param {Ext.ux.CheckColumn} this CheckColumn
                 * @param {Number} rowIndex The row index
                 * @param {Boolean} checked True if the box is to be checked
                 */
                'beforecheckchange',
                /**
                 * @event checkchange
                 * Fires when the checked state of a row changes
                 * @param {Ext.ux.CheckColumn} this CheckColumn
                 * @param {Number} rowIndex The row index
                 * @param {Boolean} checked True if the box is now checked
                 */
                'checkchange'
            );
            this.callParent(arguments);
        },

        /**
         * @private
         * Process and refire events routed from the GridView's processEvent method.
         */
        processEvent: function(type, view, cell, recordIndex, cellIndex, e, record, row) {
            var me = this,
                key = type === 'keydown' && e.getKey(),
                mousedown = type == 'mousedown';

            if (mousedown || (key == e.ENTER || key == e.SPACE)) {
                var dataIndex = me.dataIndex,
                    checked = !record.get(dataIndex);

                // Allow apps to hook beforecheckchange
                if (me.fireEvent('beforecheckchange', me, recordIndex, checked) !== false) {
                    record.set(dataIndex, checked);
                    me.fireEvent('checkchange', me, recordIndex, checked);

                    // Mousedown on the now nonexistent cell causes the view to blur, so stop it continuing.
                    if (mousedown) {
                        e.stopEvent();
                    }

                    // Selection will not proceed after this because of the DOM update caused by the record modification
                    // Invoke the SelectionModel unless configured not to do so
                    if (!me.stopSelection) {
                        view.selModel.selectByPosition({
                            row: recordIndex,
                            column: cellIndex
                        });
                    }

                    // Prevent the view from propagating the event to the selection model - we have done that job.
                    return false;
                } else {
                    // Prevent the view from propagating the event to the selection model if configured to do so.
                    return !me.stopSelection;
                }
            } else {
                return me.callParent(arguments);
            }
        },

        // Note: class names are not placed on the prototype bc renderer scope
        // is not in the header.
        renderer : function(value){
            var cssPrefix = Ext.baseCSSPrefix,
                cls = [cssPrefix + 'grid-checkheader'];

            if (value) {
                cls.push(cssPrefix + 'grid-checkheader-checked');
            }
            return '<div class="' + cls.join(' ') + '">&#160;</div>';
        }
    });