title: Leaflet fire event when tile layer loading begins and ends
body: <p>I'm using <a href="https://github.com/ebrelsford/Leaflet.loading" rel="noreferrer">Leaflet.loading</a> to display a loading icon on a leafletjs map while L.TileLayer.WMS tile layers are loading, which works well when the map is zoomed or panned. However, if WMS tile layers are switched on by the user without moving the map, the loading icon doesn't trigger. </p>
  
  <p>The Leaflet.loading instructions state:</p>
  
  <blockquote>
    <p>If you want to show the loading indicator while other AJAX requests or
    something else <em>[i.e. a WMS tile layer load]</em> is occurring, simply fire the dataloading event on your
    map when you begin loading and dataload when you are finished loading.</p>
  </blockquote>
  
  <p>How may I fire these two events on WMS tile layer load starting and finishing? </p>