Contrary to what I thought, event handlers are no big deal.
Even when you have to deal with tons of them — which I guess is tyipcally what you end up with, when you write an event driven graphics app like XVG.
You just have to come up with a scheme to keep it all organized.
As always, I go for the simplest, most understandable implementation.
Sometime with JS event handlers you see params that are never used and you say what the hey.
Then if you dig — as I do– into ze history of it, and you understand why things happened the way they did.