I have a form on my page that generates a large PDF file (can take up to 20 seconds).
Is there a way to show a throbber while the download file is being created and to hide it when the download prompt appears?

I did some checking, initially thought I could use progressive display, but figured that's not its purpose.

I figured I could attach a JS function that will trigger showing my throbber when the "Download" button is clicked, but I'm not so sure how to hide it when the download window appears.

Is there a way to do this in Tapestry?