title: Bootstrap 4 tooltip/popover using auto placement as a fallback (two placement values)
body: <p>Bootstrap 3 used to provide functionality to support data-placement="left auto" where it would show the tip on the left if there was enough room, otherwise it would calculate an auto placement.</p>
  
  <p>Bootstrap 4 does not support two placement values, you can only provide left OR auto.</p>
  
  <p>Any idea on how to achieve this in BS4?  I was working off <a href="https://stackoverflow.com/a/26081924/166231">this comment</a> along with looking at BS3.js source, but I am getting stuck trying to determine the 'current height/width' of the tooltip to be displayed and from BS3.js, what to use as the 'viewport' (I'm assuming the <code>window</code> object?)</p>