Agree that the class is too big, but I don't want to make the distinction between 'touch' and 'non-touch' handlers.

One category they could *all* fall under - and by 'they' I mean things like `handleMouseClickEvent`, `handleMouseUp` alongside these that we already talked about, - is perhaps a `SelectionManager` used by `SessionController`, and which invokes calls from, say, `SelectionController`.