given the following Grid Panel:

Ext.onReady(function() {





    var sm = new Ext.selection.CheckboxModel( {

        listeners:{

            selectionchange: function(selectionModel, selected, options){

                // Bunch of code to update store

            }

        }

    });



    var grid = Ext.create('Ext.grid.Panel', {

        features: [{

            ftype: 'summary'

        }],

        store: store,

        defaults: {               // defaults are applied to items, not the container

            sortable:true

        },

        selModel: sm,

        columns: [

            {header: 'Column 1', flex: 1, dataIndex: 'd1', summaryRenderer: function(value, summaryData, dataIndex) { return Selected Data} },

            {header: 'C2', width: 150, dataIndex: 'd2', summaryType: 'sum'},

            {header: 'C3', width: 150, dataIndex: 'd3', renderer: dRenderer, summaryType: 'sum'},

            {header: 'C4', width: 150, dataIndex: 'd4', renderer: dRenderer, summaryType: 'sum'},

            {header: 'C5', width: 150, renderer: total, summaryRenderer: grandTotal}

        ],

        width: 100%,

        title: 'Grid',

        renderTo: 'grid',

        viewConfig: {

            stripeRows: true

        }

    });

});

How does this need to be refactored to summarize the data of only those rows that are selected? I know that I probably need to override the sum function of the Summary Feature, but haven't been able to find an example or proper syntax in the docs.

Thanks!

Here was my attempt at a solution (posted on the Sencha 4.x help forum w/ no responses):

Ext.define('Ext.grid.feature.SelectedSummary', {

    extend: 'Ext.grid.feature.Summary',

    alias: 'feature.selectsummary',

    generateSummaryData: function(){

        var me = this,

            data = {},

            store = me.view.store,

            selectedRecords = me.view.selModel.selected,

            columns = me.view.headerCt.getColumnsForTpl(),

            i = 0,

            length = columns.length,

            fieldData,

            key,

            comp;



        for (i = 0, length = columns.length; i < length; ++i) {

            comp = Ext.getCmp(columns[i].id);

            val = 0;

            for(j = 0, numRecs = selectedRecords.items.length; j < numRecs; j++ ) {

                field = columns[i].dataIndex;

                rec = selectedRecords.items[j];

                console.log(rec.get(field));

                val += rec.get(field);

            }

            data[comp.dataIndex] = val;//me.getSummary(store, comp.summaryType, comp.dataIndex, false);

        }

        return data;

    }

});

But this only renders correctly on initial render and only renders when I step through the code with a debugger. There's some kind of race condition where the row gets rendered without the calculations being completed.

Any ideas? Is my question too specific? Perhaps just simple pointers on writing my own feature and adding it to a Grid Panel.