Canvas or viewer loading complete?

Hi.
I want export image of canvas on new tab when replace scene complete. I write 
this:

viewer.replaceSceneFromUrl(url);
viewer.onloadingcomplete = function () {
   window.open(canvas.toDataURL());
};

It's open blank page. So I solve this:

viewer.replaceSceneFromUrl(url);
viewer.onloadingcomplete = function () {
  setTimeout(function(){
     window.open(canvas.toDataURL());
  },3000)
};

It's ok. But setTimeout is not a good choice. How to identify the view or 
canvas is loading complete, please?

Original issue reported on code.google.com by fabien...@gmail.com on 4 Sep 2014 at 8:33

Start at viewer.replaceSceneFromUrl and the viewer.onloadingcomplete callback, then trace when the canvas is rendered relative to that callback. Reproduce the window.open(canvas.toDataURL()) example and verify that export works without a fixed delay; the issue names no file or test.