One follow-up from that I think we'd might need in the future some kind of way to illustrate other running applications, some kind of a switcher that presents some kind of cards with applications (imagine alt-tab, or the switcher from Android). This is half-way into this transition bit and half-way into a switcher application, I guess maybe some kind of a glorified launcher application that also displays current running applications to switch from. Again, the switcher application can perform the animation of those running applications like cards/snapshots of their current/previous renderered frame. 

There's no animation when switching/activating other applications, if by transition animation we refer to that. Clients can add on their own, fade-in, zoom-out, and fade-in, and zoom-in transition animation when they're started/stopped, which can effectively achieve the same thing, but agl-shell no transition/spring animation backed-in. (We can those in, backed-in into into the compositor if you believe that is where they should be, for instance desktop-shell from weston does that, but not all shells do). 

Another old feature request to review and comment on.  

Can we collaborate with GENIVI ILM?