/**
	 * Added ability to disable grouping menu
	 */
	Ext.override(Ext.grid.GroupingView, {

		beforeMenuShow: function() {

			var field = this.getGroupField();
			var g = this.hmenu.items.get('groupBy');

			if(g) {
				g.setDisabled(this.cm.config[this.hdCtxIndex].groupable === false); }

			var s = this.hmenu.items.get('showGroups');

			if(s) {
				s.setDisabled(!field && this.cm.config[this.hdCtxIndex].groupable === false);
				s.setChecked(!!field, true);
			}

		}

	});

/**
	 * Performance hack for GroupingView
	**/
	Ext.override(Ext.grid.GroupingView, {

		onLayout : function() {
	    },

		afterRender: function() {

			Ext.grid.GroupingView.superclass.afterRender.call(this);

        }

	});

	/**
	 * Added ability to define compare column using
	 * groupCompareByFieldValue
	 *
	 * @param {Object} cs
	 * @param {Object} rs
	 * @param {Object} ds
	 * @param {Object} startRow
	 * @param {Object} colCount
	 * @param {Object} stripe
	 */
	Ext.override(Ext.grid.GroupingView, {

		doRender : function(cs, rs, ds, startRow, colCount, stripe){

			if(rs.length < 1){
	            return ''; }

	        var groupField = this.getGroupField();
	        var colIndex = this.cm.findColumnIndex(groupField);

	        this.enableGrouping = !!groupField;

	        if(!this.enableGrouping || this.isUpdating){
	            return Ext.grid.GroupingView.superclass.doRender.apply(
	                    this, arguments);
	        }
	        var gstyle = 'width:'+this.getTotalWidth()+';';

	        var gidPrefix = this.grid.getGridEl().id;
	        var cfg = this.cm.config[colIndex];

	        var groupRenderer = cfg.groupRenderer || cfg.renderer;
	        var prefix = this.showGroupName ? (cfg.groupName || cfg.header) + ': ' : '';

	        var groups = [], curGroup, i, len, gid;
	        for(i = 0, len = rs.length; i < len; i++){
	            var rowIndex = startRow + i;
	            var r = rs[i];

	            if( !cfg.groupCompareByFieldValue ) {

					var gvalue = r.data[groupField];
	                var g = this.getGroup(gvalue, r, groupRenderer, rowIndex, colIndex, ds);

				} else {

					var gvalue = r.data[cfg.groupCompareByFieldValue];
					var g = r.data[cfg.groupCompareByFieldValue];

				}

	            if(!curGroup || curGroup.group != g){

					if( !cfg.groupCompareByFieldValue ) {

		                var gtext = g;

					} else {

						var gtext = this.getGroup(r.data[groupField], r, groupRenderer, rowIndex, colIndex, ds);

					}

	                gid = gidPrefix + '-gp-' + groupField + '-' + Ext.util.Format.htmlEncode(g);

					// if state is defined use it, however state is in terms of expanded
					// so negate it, otherwise use the default.
					var isCollapsed  = typeof this.state[gid] !== 'undefined' ? !this.state[gid] : this.startCollapsed;
					var gcls = isCollapsed ? 'x-grid-group-collapsed' : '';

					curGroup = {
	                    group: g,
	                    gvalue: gvalue,
	                    text: prefix + gtext,
	                    groupId: gid,
	                    startRow: rowIndex,
	                    rs: [r],
	                    cls: gcls,
	                    style: gstyle
	                };

					groups.push(curGroup);

	            } else {

					curGroup.rs.push(r);

	            }
	            r._groupId = gid;
	        }

	        var buf = [];
	        for(i = 0, len = groups.length; i < len; i++){
	            var g = groups[i];
	            this.doGroupStart(buf, g, cs, ds, colCount);
	            buf[buf.length] = Ext.grid.GroupingView.superclass.doRender.call(
	                    this, cs, g.rs, ds, g.startRow, colCount, stripe);

	            this.doGroupEnd(buf, g, cs, ds, colCount);
	        }

	        return buf.join('');
	    }

	});