title: DojoToolkit: dojox.charting.DataSeries, how to connect to data refresh event?
body: <p>I'm new to JavaScript and Dojo so please bear with me. I'm trying to create a Pie chart using DataSeries object, like this:</p>
  
  <pre><code>var skillStore = new dojo.data.ItemFileReadStore({
      url: "/data/skillhead.json"
  });
  
  function formatPieChartData(store, item) {
    var tooltips = {
      AVAILABLE: "Available agents",
      ONACD: "Agents on ACD calls",
      INACW: "Agents in ACW",
      INAUX: "Agents in AUX",
      AGINRING: "Agents with ringing phones",
      OTHER: "Agents otherwise occupied",
    };
  
    var ivalue = store.getValue(item, "value");
    var legend = store.getValue(item, "legend");
    var tooltip = tooltips[store.getValue(item, "field")];
  
    var o = { y: ivalue, legend: legend, tooltip: tooltip }
    return o;
  }
  
  /* This is how the data looks like after massaging
  var chartData = [
      { y: 10, legend: "AVAIL", tooltip: "Available agents" },
      { y: 20, legend: "ONACD", tooltip: "Agents on ACD calls" },
      { y: 30, legend: "INACW", tooltip: "Agents in ACW" },
      { y: 40, legend: "INAUX", tooltip: "Agents in AUX" },
      { y: 50, legend: "INRING", tooltip: "Agents with ringing phones" },
      { y: 60, legend: "OTHER", tooltip: "Agents otherwise occupied" }
  ];
   */
  
  var series = new dojox.charting.DataSeries(skillStore,
      { query: {
          field: new RegExp("INACW|INAUX|AGINRING|OTHER|" +
                    "AVAILABLE|ONACD")
      } },
      formatPieChartData);
  
  dojo.addOnLoad( function() {
  
  chart = new dojox.charting.Chart("chartNode");
  chart.setTheme(dojox.charting.themes.PrimaryColors);
  
  chart.addPlot("default", {
      type: "Pie",
      radius: 85,
      labels: false,
      ticks: false,
      markers: false
  });
  chart.addSeries("default", series);
  
  var highlight = new dojox.charting.action2d.Highlight(chart, "default");
  var tip = new dojox.charting.action2d.Tooltip(chart, "default");
  
  grid.startup();
  chart.render();
  
  legend = new dojox.charting.widget.Legend({
          chart: chart,
          horizontal: false,
          style: "font-size: 11px;",
          },
          "chartLegend");
  legend.startup();
  
  setTimeout(function(){ legend.refresh() }, 1000);
  });
  </code></pre>
  
  <p>It works fine, except one thing: I don't like the fixed timeout. I have to refresh legend after the data is loaded, otherwise it is not displayed; however I don't know which event to attach to in order to refresh legend right after the data is fetched. I see DataSeries class has onFetchError event but no onFetchSuccess event. How do I know that the data was loaded successfully?</p>