Progress bar on incoming deeplink

Hi,   I know you can have a progress bar on onclick buttons, but im looking for a progress bar that loads while the microflow is running.  For example my callback URL from a payment system to subscribe people takes up to 20 seconds. In this 20 seconds you only see a white screen. (this all because the connections with Afas) I know you can do this via nano flows (hide and show progress). I was thinking to make something in Java to call the java action in the begin of the flow. Is this even possible?     
1 answers

You can use the websockets push module/widget  for that.  You can show a spinner until the callback is done, but with the websocket you can send a message to the browser to hide the spinner.  BTW there are multiple websocket solutions in the marketplace.