Belt Balancer (Unofficial 2.1 Fix)

Place Balancer Parts next to each other and connect belts, undergrounds, splitters, loaders or linked belts to the
edges. All input lanes are balanced onto all output lanes.

This is an unofficial Factorio 2.1 build of Belt Balancer 2 / Belt Balancer 3 with one extra feature: it can
replace those mods in an existing save.

Why this exists

Belt Balancer 2 (2.0.9, by knoxfighter, archiehalliwell and IThundxr) does not load on Factorio 2.1. Belt Balancer 3 by
NightPablo fixes that, but a mod's script state is private to its name. If you switch an existing save from
Belt Balancer 2 to Belt Balancer 3 (or to any renamed mod) the placed balancer parts are still on the map but nothing manages
them any more, so the balancers silently stop balancing.

This mod keeps the same prototype names (balancer-part, recipes, technologies) as the originals and rebuilds its script
state from the placed entities on load: every balancer part and every belt, underground, splitter, loader and linked belt
next to one is registered again, on every surface including space platforms. About 1000 parts are processed in roughly
50 ticks (about 10 ms per tick at most), with no per-tick cost afterwards.

Installing over Belt Balancer 2 / 3

1. Disable or delete belt-balancer-2 / belt-balancer-3 (this mod is marked incompatible with them, they use identical prototype names).
2. Enable this mod and load your save. Balancers resume working after the rebuild finishes (a fraction of a second).

Not recoverable: items that were held inside a balancer's internal buffer when the old mod was removed (at most two per
output lane).

Credits and licence

Original mod by knoxfighter, archiehalliwell and IThundxr (Belt Balancer 2); Factorio 2.1 update by NightPablo (Belt Balancer 3);
2.1 fix and save-state rebuild by kfsone. MIT licensed; both upstream licence files are included.
Source and issues: https://github.com/kfsone/belt-balancer-unofficial-2-1fix