Bootstrap 3 shown/hidden events look like "shown.bs.modal",
"shown.bs.popover", etc. When subscribing to these events, you also
automatically pick up "shown" and "hidden" events. This causes a 6X
oversubscription of hidden and shown events. We fix this by filtering
out these overbroad events.
Also, don't do anything if the show/hide would be a no-op; this
also helps cut down on extraneous events.