In my web application there is a button clicking which I start downloading the file in the same window. I am incapacitated in displaying a progress bar because the response mimetype is changing and there is no way to detect file download starting to restore the button back.
Any clues on how to work around it? The problem is bit significant because I am doing a lot of operations in the background to prepare the file and if the user keeps clicking the button for a while, the server is likely to be swamped by superflous requests of all sorts.
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