title: Shiny's progress bar just delays progress
body: <p>I used Shiny's withProgress feature for a long calculation: <a href="https://shiny.rstudio.com/reference/shiny/latest/withProgress.html" rel="noreferrer">https://shiny.rstudio.com/reference/shiny/latest/withProgress.html</a></p>
  
  <p>However, it simply puts the system to sleep and I have to wait for the Sys.sleep(xx) to finish before the calculations are actually undertaken. So I don't see the point of using something that makes the calculation process seem twice as long. </p>
  
  <p>Is there some other progress bar approach that doesn't use Sys.sleep(0.25) so that calculations are actually occurring during the progress status display?</p>