Enter(), Entered(), Exit() and Exited() all passed the old loc forward, but everything except a single a case cared about the direction of the movement more than about the specific source.
Since moving multi-tile objects will have multiple sources of movement but a single direction, this change makes it easier to track their movement.
Cleaned up a lot of code around and made proc inputs compatible.
I'll add opacity support for multi-tile objects in a different PR after this is merged, as this has grown large enough and I don't want to compromise the reviewability.
Tested this locally and as expected it didn't impair movement nor produced any runtimes.
Loosely adapted from /vg/. This is an entity component system for adding behaviours to datums when inheritance doesn't quite cut it. By using signals and events instead of direct inheritance, you can inject behaviours without hacky overloads. It requires a different method of thinking, but is not hard to use correctly. If a behaviour can have application across more than one thing. Make it generic, make it a component. Atom/mob/obj event? Give it a signal, and forward it's arguments with a SendSignal() call. Now every component that want's to can also know about this happening.
e03cd1aada