Hi All

I have been going through the classes we have developed and sharing back with the community some of them that I think will be useful to others. This one I have received requests for before in this thread:
http://www.sencha.com/forum/showthread.php?10311 I no longer have access to this thread so I am posting it here.

Here is: Ext.ux.grid.CellExpander2

Extended version of Ext.ux.grid.RowExpander. This version looks for changes in the grid and saves the html of the expanded rows, it then restores the html back into the grid when the view refreshes. Allows expanders to be attached to cells instead of just rows.

Code:
/**
 * @author Will Ferrer, Ethan Brooks
 * @copyright (c) 2012, Intellectual Property Private Equity Group
 * @licensee 2012 developed under license for Switchsoft LLC http://www.switchsoft.com a "Direct response telephony company" as part of it's "VOIP Call distribution, ROI analysis platform, call recording, and IVR for inbound and outbound sales" and Run the Business Systems LLC a "Technology development investment group" as part of it's "PHP, Javascript rapid application development framework and MySQL analysis tools"
 * @license licensed under the terms of
 * the Open Source LGPL 3.0 license.  Commercial use is permitted to the extent
 * that the code/component(s) do NOT become part of another Open
Source or Commercially
 * licensed development library or toolkit without explicit permission.
 * <p>License details: <a href="http://www.gnu.org/licenses/lgpl.html"
 * target="_blank">http://www.gnu.org/licenses/lgpl.html</a></p>
* We are pretty nice just ask. We want to meet our licensees
*/
/*
history:
    03/06/10 -- took cell expander code and changed it to have the expander be inside the cell instead of next to it
*/
Ext.ns('Ext.ux.grid');

/**
 * @class Ext.ux.grid.CellExpander2
 * @extends Ext.ux.grid.RowExpander
 * Plugin (ptype = 'ux-grid-cellexpander2') extended version of Ext.ux.grid.RowExpander. This version looks for changes in the grid and saves the html of the expanded rows, it then restores the html back into the grid when the view refreshes. Allows expanders to be attached to cells instead of just rows.
 * @ptype ux-grid-cellexpander2
 */
Ext.ux.grid.CellExpander2 = Ext.extend(Ext.ux.grid.RowExpander, {
    /**
     * @cfg {String|Number|Null} storeHtmlBy
     * This is the attribute of the store record that is used to save and restore the html in the grid. If left null then the id of the store record will be used, if you are going to be using remote sorting you may need to change this value. The property of the record you use will need to be a unique identifier. If changed to a number then this is the index of the column to use the value associated with. Defaults to null
     */
    storeHtmlBy : null,
    /**
     * @cfg {String|Null} allowMultiExpansions
     * Whether or not multiple row expanders can be triggered. Defaults to false
     */
    allowMultiExpansions : false,
    /**
     * @cfg {String|Null} dontRegenContent
     * If a row has content expanded into it already, whether or not to regenerate that content based on the tpl. Defaults to true
     */
    dontRegenContent : true,
    /**
     * @cfg {String|Null} clearContentOnExpand
     * Whether or not to clear existant content when a cell is expanded. Defaults to false
     */
    clearContentOnExpand : false,
    /**
     * @cfg {String|Null} clearContentOnCollapse
     * Whether or not to clear existant content when a cell is collapsed. Defaults to false
     */
    clearContentOnCollapse : false,
    /**
     * @cfg {String|Null} clearContentOnExpand
     * Whether or not to clean up content when a cell is expanded. Defaults to false
     */
    cleanUpOnExpand : false,
    /**
     * @cfg {String|Null} clearContentOnCollapse
     * Whether or not to clean up when a cell is collapsed. Defaults to false
     */
    cleanUptOnCollapse : false,
    /**
    * @cfg{Object} expandable
    * Whether or not the column should display an exapnder. Defaults to true.
    */
    expandable : true,
    /**
    * @cfg{Object} baseRenderer
    * The render to use for this column -- result given by this render will have an expander box added to it before it is displayed. Defaults to Ext.grid.ColumnModel.defaultRenderer.
    */
    baseRenderer : Ext.grid.ColumnModel.defaultRenderer,
    /**
    * @cfg{Object} displayTemplate
    * The template to use when rendering the contents of each cell. The template should contain a placeholder for: {value}. This placeholder is where the results of the baseRenderer will be populated to.
    */
    displayTemplate : '<div class="x-grid3-row-expander x-grid3-row-collapsed">&#160;</div><div style="float:left">{value}</div>',
    /**
    * @cfg {Boolean} cleanUpOnRefresh
    * trigger clean up when refresh happens. Defaults to false.
    */
    cleanUpOnRefresh : false,
    /**
    * @cfg {Boolean} fixRolloverHighlight
    * Tries to prevent multiple row rollovers visual bugs. Defaults to true.
    */
    fixRolloverHighlight : true,
    /**
    * @private internal config {Object} storedHtml
    * Used to store the html that will be restored to the grid.
    */
    storedHtml : {},
    /**
    * @private internal config {Number} randKey
    * There is an odd bug where the storedHtml of all expanders is being shared by parent grids and child grids. It makes no sence at all so I am storing html in a sub objects based on a random key.
    */
    randKey : null,
    id : null,
    width : undefined,
    menuDisabled : false,
    fixed : false,
    getRowClass : function(record, rowIndex, p, ds){
        return 'x-grid3-row-collapsed';
    },
    hideable : true,
    /** Public Function: clearStoredHtml
    * clears the stored html. May also be used to clean up the component manager.
    * @param {Boolean} cleanUp (Optional) whether to clean the componentManager or not. Defaults to false
    */
    clearStoredHtml : function (cleanUp) {
        var cleanUp = (Ext.isEmpty(cleanUp))?false:cleanUp,
            randKey = this.randKey;
        this.storedHtml = {};
        this.storedHtml[this.randKey] = {};
        if (cleanUp) {
            this.cleanUp();
        }
    },
    /** Public Function: cleanUp
    * Used to clean up the component manager destroying any orphaned components
    */
    cleanUp : function () {
        var items = Ext.ComponentMgr.all.items,
            curItem, n;
        for(n=0;n<items.length;n++){
            curItem = items[n];
            if (!Ext.isEmpty(curItem.rendered) && (Ext.isEmpty(curItem.el) || !Ext.fly(curItem.el)) && !Ext.isEmpty(curItem.cleanUpAfterExpand) && curItem.cleanUpAfterExpand) {
                if (!Ext.isEmpty(curItem.remove)) {
                    curItem.remove(true);
                }
                if (!Ext.isEmpty(curItem.destroy)) {
                    curItem.destroy(true);
                }
                //curItem = undefined;
                //delete curItem;
            }
        }
        
    },
    // @private
    constructor : function (config) {
        Ext.ux.grid.CellExpander2.superclass.constructor.call(this, config);
        this.addEvents({
            /**
             * @event beforeexpand
             * Fires before the row expands. Have the listener return false to prevent the row from expanding.
             * @param {Object} this RowExpander object.
             * @param {Object} Ext.data.Record Record for the selected row.
             * @param {Object} body body element for the secondary row.
             * @param {Number} rowIndex The current row index.
             * @param {Number} cellIndex The current cell index.
             * @param {Object} column The column object of the column after the row expander column.
             * @param {Object} value The value  of the column after the row expander column.
             * @param {Boolean} hasContent Whether or not there is html in the body of the effected row -- if there is html you may not wish to regenerate it as this can cause a memory leak.
             */
            beforeexpand: true,
            /**
             * @event expand
             * Fires after the row expands.
             * @param {Object} this RowExpander object.
             * @param {Object} Ext.data.Record Record for the selected row.
             * @param {Object} body body element for the secondary row.
             * @param {Number} rowIndex The current row index.
             * @param {Number} cellIndex The current cell index.
             * @param {Object} column The column object of the column after the row expander column.
             * @param {Object} value The value  of the column after the row expander column.
             * @param {Boolean} hasContent Whether or not there is html in the body of the effected row -- if there is html you may not wish to regenerate it as this can cause a memory leak.
             */
            expand: true,
            /**
             * @event beforecollapse
             * Fires before the row collapses. Have the listener return false to prevent the row from collapsing.
             * @param {Object} this RowExpander object.
             * @param {Object} Ext.data.Record Record for the selected row.
             * @param {Object} body body element for the secondary row.
             * @param {Number} rowIndex The current row index.
             * @param {Number} cellIndex The current cell index.
             * @param {Object} column The column object of the column after the row expander column.
             * @param {Object} value The value  of the column after the row expander column.
             * @param {Boolean} hasContent Whether or not there is html in the body of the effected row -- if there is html you may not wish to regenerate it as this can cause a memory leak.
             */
            beforecollapse: true,
            /**
             * @event collapse
             * Fires after the row collapses.
             * @param {Object} this RowExpander object.
             * @param {Object} Ext.data.Record Record for the selected row.
             * @param {Object} body body element for the secondary row.
             * @param {Number} rowIndex The current row index.
             * @param {Number} cellIndex The current cell index.
             * @param {Object} column The column object of the column after the row expander column.
             * @param {Object} value The value  of the column after the row expander column.
             * @param {Boolean} hasContent Whether or not there is html in the body of the effected row -- if there is html you may not wish to regenerate it as this can cause a memory leak.
             */
            collapse: true
        });
    },
    // @private
    init : function (grid) {
        Ext.ux.grid.CellExpander2.superclass.init.call(this, grid);
        this.grid.view.on('beforerefresh', this.storeHtml, this);
        this.grid.store.on('beforeload', this.storeHtml, this);
        this.grid.view.on('refresh', this.onRefresh, this);
        this.grid.on('viewready', this.markRows, this);
        this.grid.on('rowsinserted', this.markRows, this);
        
        this.grid.on('rowmouseover', this.onRowMouseOver, this);
        grid.cellExpander = this;
        
        this.randKey = Math.floor(Math.random() * 9999999999999);
        
        this.storedHtml = {};
        this.storedHtml[this.randKey] = {};
    },
    // @private
    onRowMouseOver : function (grid, row, e) {
        var store = this.grid.getStore(),
            view = this.grid.getView(),
            highlightedColumns = [],
            n, row;

        for(n=0;n<store.data.items.length;n++) {
            row = view.getRow(n);
            if (row) {
                if (Ext.fly(row).hasClass('x-grid3-row-over')) {
                    highlightedColumns.push(row);
                }
            }
        }
        for(n=0; n<highlightedColumns.length-1;n++){
            row = highlightedColumns[n];
            Ext.fly(row).removeClass('x-grid3-row-over');
        }
    },
    // @private
    onRender: function() {
        var grid = this.grid;
        var mainBody = grid.getView().mainBody;
        if (typeof(this.storeHtmlBy) == 'number') {
            this.storeHtmlBy = this.grid.colModel.config[this.storeHtmlBy].dataIndex;
        }
        mainBody.on('mousedown', this.onMouseDown, this, {delegate: '.x-grid3-row-expander'});
        /*if (this.expandOnEnter) {
            this.keyNav = new Ext.KeyNav(this.grid.getGridEl(), {
                'enter' : this.onEnter,
                scope: this
            });
        }
        if (this.expandOnDblClick) {
            grid.on('rowdblclick', this.onRowDblClick, this);
        }*/
    },
    // @private
    onMouseDown : function(e, t){
        e.stopEvent();
        e.stopPropagation();
        var row = e.getTarget('.x-grid3-row'),
            cell = e.getTarget('.x-grid3-cell-inner');
        this.toggleRow(row, cell);
    },
    // @private
    renderer : function(value, cell, record, row, col, store){
        var value,
            template = new Ext.Template(this.displayTemplate),
            populateData;
        if (!Ext.isEmpty(this.originalRenderer)) {
            value = (typeof(this.originalRenderer)=='string')?Ext.util.Format[this.originalRenderer](value, cell, record, row, col, store):this.originalRenderer(value, cell, record, row, col, store);
        }
        value = (typeof(this.baseRenderer)=='string')?Ext.util.Format[this.baseRenderer](value, cell, record, row, col, store):this.baseRenderer(value, cell, record, row, col, store);
        populateData = {
            value : value
        };
        parsedString = template.apply(populateData);
        return parsedString;
    },
    // @private
    beforeExpand : function(record, body, rowIndex, cellIndex, column, value, hasContent){
        if(this.fireEvent('beforeexpand', this, record, body, rowIndex, cellIndex, column, value, hasContent) !== false){
            if(this.tpl && this.lazyRender && !hasContent){
                body.innerHTML = this.getBodyContent(record, rowIndex);
            }
            return true;
        }else{
            return false;
        }
    },
    // @private
    storeHtml : function () {
        var store = this.grid.getStore(),
            view = this.grid.getView(),
            storeHtmlBy = this.storeHtmlBy,
            randKey = this.randKey,
            n, n2, record, recordIndex, row, rowKey, expanded, body, storedBody, el, key, expanders;

        for(n=0;n<store.data.items.length;n++) {
            row = view.getRow(n);
            if (row) {
                expanded = !Ext.fly(row).hasClass('x-grid3-row-collapsed');

                if (expanded) {
                    rowKey = Ext.fly(row).getAttribute('rowexpanderkey');
                    body =  this.findRowBody(row);
                    //body = Ext.DomQuery.selectNode('tr:nth(2) div.x-grid3-row-body', row);
                    storedBody = Ext.fly(body).child('*');
                    
                    if (Ext.isEmpty(this.storedHtml[randKey][rowKey])) {
                        this.storedHtml[randKey][rowKey] = {};
                    }
                    
                    this.storedHtml[randKey][rowKey]['body'] = storedBody;
                    this.storedHtml[randKey][rowKey]['expanded'] = expanded;
                }
            }
        }
    },
    // @private
    onRefresh : function (view) {
        if (this.cleanUpOnRefresh) {
            this.clearStoredHtml();
            this.cleanUp();
        }
        var store = this.grid.getStore(),
            view = this.grid.getView(),
            storeHtmlBy = this.storeHtmlBy,
            storedHtml = this.storedHtml,
            randKey = this.randKey,
            obj, record, recordIndex, row,  body, expanded, expandedColumn, storedBody, curColumn, rowKey, cell, cellIndex, columnId, column, content,
            columnCount = this.grid.colModel.getColumnCount(true);

        for(obj in storedHtml[randKey]) {
            storedBody = storedHtml[randKey][obj]['body'];
            expanded = storedHtml[randKey][obj]['expanded'];
            expandedColumn = storedHtml[randKey][obj]['expandedColumn'];
            if (!Ext.isEmpty(obj) && !Ext.isEmpty(storedBody)) {
                if (!Ext.isEmpty(storeHtmlBy)) {
                    recordIndex = store.findBy(function (record, id) {
                        return (record.get(storeHtmlBy)==obj);
                    });
                    record = store.getAt(recordIndex);
                } else {
                    record = store.getById(obj);
                }

                if (!Ext.isEmpty(record) && record) {
                    if (!Ext.isEmpty(expanded) && expanded) {
                        row = view.getRow(recordIndex);
                        Ext.fly(row).removeClass('x-grid3-row-collapsed');
                        body =  this.findRowBody(row);
                        //body = Ext.DomQuery.selectNode('tr:nth(2) div.x-grid3-row-body', row);
                        Ext.fly(body).appendChild(storedBody);
                        cells = Ext.fly(row).select('.x-grid3-cell-inner');
                        for(n2=0;n2<columnCount;n2++){
                            cell = cells.elements[n2];
                            cellIndex = this.grid.view.findCellIndex(cell);
                            columnId = this.grid.colModel.getColumnId(cellIndex);
                            column = this.grid.colModel.getColumnById(columnId);
                            if (column.dataIndex == expandedColumn) {
                                Ext.fly(cell).replaceClass('x-grid3-row-collapsed', 'x-grid3-row-expanded');
                            } else {
                                Ext.fly(cell).replaceClass('x-grid3-row-expanded', 'x-grid3-row-collapsed');
                            }
                        }
                    }
                }
            }
        }
        
        this.markRows();
        this.storeHtml();
    
    },
    // @private
    markRows : function () {
        var view = store = this.grid.getView(),
            store = this.grid.getStore(),
            storeHtmlBy = this.storeHtmlBy;
        for(n=0;n<store.data.items.length;n++) {
            record = store.data.items[n];
            recordIndex = store.indexOf(record);
            row = view.getRow(recordIndex);
            if (row) {
                if (!Ext.isEmpty(storeHtmlBy)) {
                    key = record.get(storeHtmlBy);
                } else {
                    key = record.id;
                }
                
                Ext.fly(row).set({rowexpanderkey:key});
            }
        }
    },
    // @private
    toggleRow : function(row, cell){
        var row = (typeof row == 'number')?this.grid.view.getRow(row):row;
            cell = (typeof cell == 'number')?this.grid.view.getCell(cell):cell,
            isExpanded = Ext.fly(cell).hasClass('x-grid3-row-expanded');
        this.storeHtml();
        if (!this.allowMultiExpansions) {
            Ext.fly(row).select('.x-grid3-row-expanded').replaceClass('x-grid3-row-expanded', 'x-grid3-row-collapsed');
            Ext.fly(row).replaceClass('x-grid3-row-collapsed', '');
        }
        this[isExpanded ? 'collapseRow' : 'expandRow'](row, cell);
    },
    // @private
    findRowBody : function (row) {
        bodyTr =Ext.DomQuery.selectNode('tr.x-grid3-row-body-tr', row),
        body = Ext.DomQuery.selectNode('div.x-grid3-row-body', bodyTr);
        return body;
    },
    // @private
    expandRow : function(row, cell){
        var row = (typeof row == 'number')?this.grid.view.getRow(row):row;
            cell = (typeof cell == 'number')?this.grid.view.getCell(cell):cell;
            cellIndex = this.grid.view.findCellIndex(cell),
            rowIndex = row.rowIndex,
            columnId = this.grid.colModel.getColumnId(cellIndex),
            column = this.grid.colModel.getColumnById(columnId),
            record = this.grid.store.getAt(rowIndex),
            value = record.get(column.dataIndex),
            body = this.findRowBody(row);
            //body = Ext.DomQuery.selectNode('tr:nth(2) div.x-grid3-row-body', row);
        //Chrome breaks if you don't put these as with a seperate var -- chrome is apparently retarded.
        var hasContent = !Ext.isEmpty(body.innerHTML),
            content, dataIndex = column.dataIndex,
            rowKey = Ext.fly(row).getAttribute('rowexpanderkey'),
            randKey = this.randKey;
        if(this.beforeExpand(record, body, rowIndex, cellIndex, column, value, hasContent)){
            this.state[record.id] = true;
            Ext.fly(cell).replaceClass('x-grid3-row-collapsed', 'x-grid3-row-expanded');
            Ext.fly(row).removeClass('x-grid3-row-collapsed');
            
            if (Ext.isEmpty(this.storedHtml[randKey][rowKey])) {
                this.storedHtml[randKey][rowKey] = {};
            }
            
            this.storedHtml[randKey][rowKey]['expandedColumn'] = dataIndex;
            //this.storedHtml[randKey][rowKey]['rand'] = this.rand;
            
            if(this.clearContentOnExpand && hasContent){
                content = Ext.fly(body).child('*');
                if (!Ext.isEmpty(content.remove)) {
                    content.remove();
                } else {
                    body.innerHTML = null;
                }
                hasContent = false;
            }
            if(this.cleanUpOnExpand){
                this.cleanUp();
            }
            this.fireEvent('expand', this, record, body, rowIndex, cellIndex, column, value, hasContent);
        }
    },
    // @private
    collapseRow : function(row, cell){
        var row = (typeof row == 'number')?this.grid.view.getRow(row):row;
            cell = (typeof cell == 'number')?this.grid.view.getCell(cell):cell;
            cellIndex = this.grid.view.findCellIndex(cell),
            rowIndex = row.rowIndex,
            columnId = this.grid.colModel.getColumnId(cellIndex),
            column = this.grid.colModel.getColumnById(columnId),
            record = this.grid.store.getAt(rowIndex),
            value = record.get(column.dataIndex),
            //body = Ext.DomQuery.selectNode('tr:nth(2) div.x-grid3-row-body', row),
            bodyTr =Ext.DomQuery.selectNode('tr.x-grid3-row-body-tr', row),
            body =  this.findRowBody(row),
            hasContent = !Ext.isEmpty(body.innerHTML),
            randKey = this.randKey,
            rowKey = Ext.fly(row).getAttribute('rowexpanderkey');
            
        if(this.fireEvent('beforecollapse', this, record, body, rowIndex, cellIndex, column, value, hasContent) !== false){
            this.state[record.id] = false;
            Ext.fly(cell).replaceClass('x-grid3-row-expanded', 'x-grid3-row-collapsed');
            Ext.fly(row).addClass('x-grid3-row-collapsed');
            
            if (Ext.isEmpty(this.storedHtml[rowKey])) {
                this.storedHtml[randKey][rowKey] = {};
            }
            
            this.storedHtml[randKey][rowKey]['expanded'] = false;
            this.storedHtml[randKey][rowKey]['expandedColumn'] = null;
            
            if(this.clearContentOnCollapse && hasContent){
                content = Ext.fly(body).child('*');
                if (!Ext.isEmpty(content.remove)) {
                    content.remove();
                } else {
                    body.innerHTML = null;
                }
                hasContent = false;
            }
            if(this.cleanUptOnCollapse){
                this.cleanUp();
            }
            this.fireEvent('collapse', this, record, body, rowIndex, cellIndex, column, value, hasContent);
        }
    }
});

Ext.preg('ux-grid-cellexpander2', Ext.ux.grid.CellExpander2);
//backwards compat
Ext.grid.CellExpander2 = Ext.ux.grid.CellExpander2;
Best regards

Will Ferrer (Run the Business)