title: How to display a busy indicator in a shiny app?
body: <p>Note : I have read almost all the discussions on this object in shiny googlegroups and here in SO.</p>
  <p>I need an indicator that shows the shiny server is busy. I have tried <a href="https://github.com/rstudio/shiny-incubator" rel="nofollow noreferrer">shiny-incubator</a>, however, the problem is that I can't set a max for progress bar.<br />
  I don't want something like this : <a href="https://shiny.rstudio.com/gallery/progress-bar-example.html" rel="nofollow noreferrer">https://shiny.rstudio.com/gallery/progress-bar-example.html</a></p>
  <p>What I need is something that:</p>
  <ol>
  <li>shows a busy indicator message and bar (i.e just a simple animated bar, do not need to show a filling bar) as long as the server is calculating</li>
  <li>it is shown in no matter which tab you are viewing. (not only in the related tab, but on top of the tabset)</li>
  </ol>