title: Indicate Loading In Browser When Downloading File
body: <p>On our web application, we have loads of attachments, some static (from DB) and some dynamic (generated), some of the generated files take really long (<code>Content-Disposition: Attachment</code>)
  to download, and the user will click away sometimes. is there anyway to show and <strong>HIDE</strong> a loader as soon as the file is actually served to the browser?</p>
  
  <p>I have looked for similar questions on stackoverflow and there are, but none of them with useful answers: for <a href="https://stackoverflow.com/questions/7283058/how-to-display-and-remove-a-loading-gif-when-downloading-a-file">example</a>.</p>
  
  <p>Is this a viable question or should i just try to increase the speed at which the files are generated?</p>