[wyuenho]

You have been able to emulate cooperative multitasking using callbacks since at least the 70s with lisp. There's always been some form of concurrency in any lisp, the problem is, the event listening/emitter pattern is pretty much not a thing in Emacs, so you can't fire a custom event and hope it will drop into the event loop and get responded to by whatever is listening, because it's not an event loop, it's a command loop. The types of events you can respond to is fixed.