The source code

    /**
     * @class Ext.grid.EditorGridPanel
     * @extends Ext.grid.GridPanel
     * This class extends the {@link Ext.grid.GridPanel GridPanel Class} to provide cell editing
     * on selected {@link Ext.grid.Column columns}. The editable columns are specified by providing
     * an {@link Ext.grid.ColumnModel#editor editor} in the {@link Ext.grid.Column column configuration}.
     * Editability of columns may be controlled programatically by inserting an implementation
     * of {@link Ext.grid.ColumnModel#isCellEditable isCellEditable} into the
     * {@link Ext.grid.ColumnModel ColumnModel}.
     * Editing is performed on the value of the field specified by the column's
     * {@link Ext.grid.ColumnModel#dataIndex dataIndex} in the backing {@link Ext.data.Store Store}
     * (so if you are using a {@link Ext.grid.ColumnModel#setRenderer renderer} in order to display
     * transformed data, this must be accounted for).
     * If a value-to-description mapping is used to render a column, then a {@link Ext.form.Field#ComboBox ComboBox}
     * which uses the same {@link Ext.form.Field#valueField value}-to-{@link Ext.form.Field#displayFieldField description}
     * mapping would be an appropriate editor.
     * If there is a more complex mismatch between the visible data in the grid, and the editable data in
     * the {@link Edt.data.Store Store}, then code to transform the data both before and after editing can be
     * injected using the {@link #beforeedit} and {@link #afteredit} events.
     * @constructor
     * @param {Object} config The config object
     * @xtype editorgrid
     */
    Ext.grid.EditorGridPanel = Ext.extend(Ext.grid.GridPanel, {
        /**
         * @cfg {Number} clicksToEdit
         * The number of clicks on a cell required to display the cell's editor (defaults to 2).
         * Setting this option to 'auto' means that mousedown on the selected cell starts
         * editing that cell.
         */
        clicksToEdit: 2,

        /**
        * @cfg {Boolean} forceValidation
        * True to force validation even if the value is unmodified (defaults to false)
        */
        forceValidation: false,

        // private
        isEditor : true,
        // private
        detectEdit: false,

    	/**
    	 * @cfg {Boolean} autoEncode
    	 * True to automatically HTML encode and decode values pre and post edit (defaults to false)
    	 */
    	autoEncode : false,

    	/**
    	 * @cfg {Boolean} trackMouseOver @hide
    	 */
        // private
        trackMouseOver: false, // causes very odd FF errors

        // private
        initComponent : function(){
            Ext.grid.EditorGridPanel.superclass.initComponent.call(this);

            if(!this.selModel){
                /**
                 * @cfg {Object} selModel Any subclass of AbstractSelectionModel that will provide the selection model for
                 * the grid (defaults to {@link Ext.grid.CellSelectionModel} if not specified).
                 */
                this.selModel = new Ext.grid.CellSelectionModel();
            }

            this.activeEditor = null;

    	    this.addEvents(
                /**
                 * @event beforeedit
                 * Fires before cell editing is triggered. The edit event object has the following properties

                 *
                 * grid - This grid
                 * record - The record being edited
                 * field - The field name being edited
                 * value - The value for the field being edited.
                 * row - The grid row index
                 * column - The grid column index
                 * cancel - Set this to true to cancel the edit or return false from your handler.
                 *
                 * @param {Object} e An edit event (see above for description)
                 */
                "beforeedit",
                /**
                 * @event afteredit
                 * Fires after a cell is edited. The edit event object has the following properties

                 *
                 * grid - This grid
                 * record - The record being edited
                 * field - The field name being edited
                 * value - The value being set
                 * originalValue - The original value for the field, before the edit.
                 * row - The grid row index
                 * column - The grid column index
                 *
                 *
                 *
    grid.on('afteredit', afterEdit, this );

    function afterEdit(e) {
        // execute an XHR to send/commit data to the server, in callback do (if successful):
        e.record.commit();
    };
                 *
                 * @param {Object} e An edit event (see above for description)
                 */
                "afteredit",
                /**
                 * @event validateedit
                 * Fires after a cell is edited, but before the value is set in the record. Return false
                 * to cancel the change. The edit event object has the following properties

                 *
                 * grid - This grid
                 * record - The record being edited
                 * field - The field name being edited
                 * value - The value being set
                 * originalValue - The original value for the field, before the edit.
                 * row - The grid row index
                 * column - The grid column index
                 * cancel - Set this to true to cancel the edit or return false from your handler.
                 *
                 * Usage example showing how to remove the red triangle (dirty record indicator) from some
                 * records (not all).  By observing the grid's validateedit event, it can be cancelled if
                 * the edit occurs on a targeted row (for example) and then setting the field's new value
                 * in the Record directly:
                 *
    grid.on('validateedit', function(e) {
      var myTargetRow = 6;

      if (e.row == myTargetRow) {
        e.cancel = true;
        e.record.data[e.field] = e.value;
      }
    });
                 *
                 * @param {Object} e An edit event (see above for description)
                 */
                "validateedit"
            );
        },

        // private
        initEvents : function(){
            Ext.grid.EditorGridPanel.superclass.initEvents.call(this);

            this.on("bodyscroll", this.stopEditing, this, [true]);
            this.on("columnresize", this.stopEditing, this, [true]);

            if(this.clicksToEdit == 1){
                this.on("cellclick", this.onCellDblClick, this);
            }else {
                if(this.clicksToEdit == 'auto' && this.view.mainBody){
                    this.view.mainBody.on("mousedown", this.onAutoEditClick, this);
                }
                this.on("celldblclick", this.onCellDblClick, this);
            }
        },

        // private
        onCellDblClick : function(g, row, col){
            this.startEditing(row, col);
        },

        // private
        onAutoEditClick : function(e, t){
            if(e.button !== 0){
                return;
            }
            var row = this.view.findRowIndex(t);
            var col = this.view.findCellIndex(t);
            if(row !== false && col !== false){
                this.stopEditing();
                if(this.selModel.getSelectedCell){ // cell sm
                    var sc = this.selModel.getSelectedCell();
                    if(sc && sc[0] === row && sc[1] === col){
                        this.startEditing(row, col);
                    }
                }else{
                    if(this.selModel.isSelected(row)){
                        this.startEditing(row, col);
                    }
                }
            }
        },

        // private
        onEditComplete : function(ed, value, startValue){
            this.editing = false;
            this.activeEditor = null;
            ed.un("specialkey", this.selModel.onEditorKey, this.selModel);
    		var r = ed.record;
            var field = this.colModel.getDataIndex(ed.col);
            value = this.postEditValue(value, startValue, r, field);
            if(this.forceValidation === true || String(value) !== String(startValue)){
                var e = {
                    grid: this,
                    record: r,
                    field: field,
                    originalValue: startValue,
                    value: value,
                    row: ed.row,
                    column: ed.col,
                    cancel:false
                };
                if(this.fireEvent("validateedit", e) !== false && !e.cancel && String(value) !== String(startValue)){
                    r.set(field, e.value);
                    delete e.cancel;
                    this.fireEvent("afteredit", e);
                }
            }
            this.view.focusCell(ed.row, ed.col);
        },

        /**
         * Starts editing the specified for the specified row/column
         * @param {Number} rowIndex
         * @param {Number} colIndex
         */
        startEditing : function(row, col){
            this.stopEditing();
            if(this.colModel.isCellEditable(col, row)){
                this.view.ensureVisible(row, col, true);
                var r = this.store.getAt(row);
                var field = this.colModel.getDataIndex(col);
                var e = {
                    grid: this,
                    record: r,
                    field: field,
                    value: r.data[field],
                    row: row,
                    column: col,
                    cancel:false
                };
                if(this.fireEvent("beforeedit", e) !== false && !e.cancel){
                    this.editing = true;
                    var ed = this.colModel.getCellEditor(col, row);
                    if(!ed){
                        return;
                    }
                    if(!ed.rendered){
                        ed.render(this.view.getEditorParent(ed));
                    }
                    (function(){ // complex but required for focus issues in safari, ie and opera
                        ed.row = row;
                        ed.col = col;
                        ed.record = r;
                        ed.on("complete", this.onEditComplete, this, {single: true});
                        ed.on("specialkey", this.selModel.onEditorKey, this.selModel);
                        /**
                         * The currently active editor or null
                          * @type Ext.Editor
                         */
                        this.activeEditor = ed;
                        var v = this.preEditValue(r, field);
                        ed.startEdit(this.view.getCell(row, col).firstChild, v === undefined ? '' : v);
                    }).defer(50, this);
                }
            }
        },

        // private
        preEditValue : function(r, field){
            var value = r.data[field];
            return this.autoEncode && typeof value == 'string' ? Ext.util.Format.htmlDecode(value) : value;
        },

        // private
    	postEditValue : function(value, originalValue, r, field){
    		return this.autoEncode && typeof value == 'string' ? Ext.util.Format.htmlEncode(value) : value;
    	},

        /**
         * Stops any active editing
         * @param {Boolean} cancel (optional) True to cancel any changes
         */
        stopEditing : function(cancel){
            if(this.activeEditor){
                this.activeEditor[cancel === true ? 'cancelEdit' : 'completeEdit']();
            }
            this.activeEditor = null;
        }
    });
    Ext.reg('editorgrid', Ext.grid.EditorGridPanel);