FileDownloader indication of processing?


I am using OnDemandFileDownloader as described here:
The server gets some parameters from the UI to process an excel file download (so the content of the excel varies based on input parameters). The processing may take a longer time, and I would like to show some kind of a notification that download is processing (ideally, to show the spinner loading up until the point the download appears for the user). Right now there are several seconds of gap between download click and before the actual download gets ready, which can be confusing for the user. Is there some sort of solution for this problem? Something like the upload component, where there are listeners for started/success/failed events?

Thanks for any help in advance.