    /**
     * @class Ext.grid.feature.Feature
     * @extends Ext.util.Observable
     *
     * A feature is a type of plugin that is specific to the {@link Ext.grid.Panel}. It provides several
     * hooks that allows the developer to inject additional functionality at certain points throughout the
     * grid creation cycle. This class provides the base template methods that are available to the developer,
     * it should be extended.
     *
     * There are several built in features that extend this class, for example:
     *
     *  - {@link Ext.grid.feature.Grouping} - Shows grid rows in groups as specified by the {@link Ext.data.Store}
     *  - {@link Ext.grid.feature.RowBody} - Adds a body section for each grid row that can contain markup.
     *  - {@link Ext.grid.feature.Summary} - Adds a summary row at the bottom of the grid with aggregate totals for a column.
     *
     * ## Using Features
     * A feature is added to the grid by specifying it an array of features in the configuration:
     *
     *     var groupingFeature = Ext.create('Ext.grid.feature.Grouping');
     *     Ext.create('Ext.grid.Panel', {
     *         // other options
     *         features: [groupingFeature]
     *     });
     *
     * @abstract
     */
    Ext.define('Ext.grid.feature.Feature', {
        extend: 'Ext.util.Observable',
        alias: 'feature.feature',

        isFeature: true,
        disabled: false,

        /**
         * @property {Boolean}
         * Most features will expose additional events, some may not and will
         * need to change this to false.
         */
        hasFeatureEvent: true,

        /**
         * @property {String}
         * Prefix to use when firing events on the view.
         * For example a prefix of group would expose "groupclick", "groupcontextmenu", "groupdblclick".
         */
        eventPrefix: null,

        /**
         * @property {String}
         * Selector used to determine when to fire the event with the eventPrefix.
         */
        eventSelector: null,

        /**
         * @property {Ext.view.Table}
         * Reference to the TableView.
         */
        view: null,

        /**
         * @property {Ext.grid.Panel}
         * Reference to the grid panel
         */
        grid: null,

        /**
         * Most features will not modify the data returned to the view.
         * This is limited to one feature that manipulates the data per grid view.
         */
        collectData: false,

        getFeatureTpl: function() {
            return '';
        },

        /**
         * Abstract method to be overriden when a feature should add additional
         * arguments to its event signature. By default the event will fire:
         * - view - The underlying Ext.view.Table
         * - featureTarget - The matched element by the defined {@link #eventSelector}
         *
         * The method must also return the eventName as the first index of the array
         * to be passed to fireEvent.
         */
        getFireEventArgs: function(eventName, view, featureTarget, e) {
            return [eventName, view, featureTarget, e];
        },

        /**
         * Approriate place to attach events to the view, selectionmodel, headerCt, etc
         */
        attachEvents: function() {

        },

        getFragmentTpl: function() {
            return;
        },

        /**
         * Allows a feature to mutate the metaRowTpl.
         * The array received as a single argument can be manipulated to add things
         * on the end/begining of a particular row.
         */
        mutateMetaRowTpl: function(metaRowTplArray) {

        },

        /**
         * Allows a feature to inject member methods into the metaRowTpl. This is
         * important for embedding functionality which will become part of the proper
         * row tpl.
         */
        getMetaRowTplFragments: function() {
            return {};
        },

        getTableFragments: function() {
            return {};
        },

        /**
         * Provide additional data to the prepareData call within the grid view.
         * @param {Object} data The data for this particular record.
         * @param {Number} idx The row index for this record.
         * @param {Ext.data.Model} record The record instance
         * @param {Object} orig The original result from the prepareData call to massage.
         */
        getAdditionalData: function(data, idx, record, orig) {
            return {};
        },

        /**
         * Enable a feature
         */
        enable: function() {
            this.disabled = false;
        },

        /**
         * Disable a feature
         */
        disable: function() {
            this.disabled = true;
        }

    });