Support events like "update-start" and "update-end"

[abakirov]

In some cases loading data takes several seconds. For anything above 1-2 sec we would like to show a progress bar. Please support events like update-start and update-end to facilitate this. This could be something similar to corresponding events in FeatureLayer.

[abakirov]

Hi,

I'm trying to use the events but they do not seem work:

  var chart = new Cedar({
    "specification":"../../../cedar/data/templates/scatter.json",
    "dataset":{
      "url":"http://maps2.dcgis.dc.gov/dcgis/rest/services/DCGIS_DATA/Education_WebMercator/MapServer/5",
      "query":{},
      "mappings":{
        "x": {"field":"POPULATION_ENROLLED_2008","label":"Enrolment 2008"},
        "y": {"field":"SQUARE_FOOTAGE","label":"Square Footage"},
        "color":{"field":"FACUSE","label":"Facility Type"}
      }
    }
  });

  chart.on('update-start', function() {
    console.log('update-start'); //never called
  });

  //render the chart
  chart.show({
    elementId: "#chart"
  });

This line is never called: console.log('update-start');

Not supported yet?

Thanks

[benheb]

@abakirov could be I just didn't implement in the way you'd expect, but it should work. I think "update-start" will only fire when "update()" is called on the chart. Try changing your example to "update-end" and see if it fires when the chart has loaded:

chart.on('update-end', function() {
    console.log('update-end'); //should be called.. 
});

[benheb]

p.s. start will get fired in this case:

  setTimeout(function() {
    chart.update();
  },4000);

  chart.on('update-start', function() {
    console.log('update start!');
  });

[arthaddad]

Why wouldn't the update_start fire on .show() ??

[benheb]

I don't know, I can probably change. I think my logic was that if we are calling .show() then we already know that 'update-start' is firing, and that it would be redundant, whereas update-end gets fired after the chart finishes updating, something we wouldn't otherwise know. In the example above:

chart.on('update-start', function() {
  callSomeFunction();
});

//render the chart
chart.show({
  elementId: "#chart"
});

Why not just do:

//render the chart
chart.show({
  elementId: "#chart"
});
callSomeFunction();

Maybe flawed logic, but that was my thinking anyway. I'll take a look at making the change.