Getting progress information with app.request.json()

I am using app.request.json() to get and store my app data from a server. I now want to have a progressbar on the home page where the progress is set using app.progressbar.set() with a live percentage from the request.

Is this possible? I couldn’t see anything in the Request / Ajax documentation about an event for progress.

Anyone got any ideas?

Request returns XHR so