Callback: Custom station layout

Custom station layout (24)

After applying the values from station prop. 0E, this callback is used to further customize the tile layout.

It is called once for every tile that is being built, and returns the new tile type to build in its place or to leave the tile as defined by prop. 0E or TTD's default if the callback fails. The only possible return values are 00, 02, 04 and 06. Their meaning is the same as in prop. 0E.

Since the station hasn't yet been built, variables 40+x and 80+x are not available, instead variable 10 (extra callback info 1) contains the same information as variable 41 would contain. For the same reason, it uses the same cargo type in action 3 as the construction menu does (i.e., type FF if defined or else the default).

This callback is used always and does not need setting a bit in the action 0 property to activate it.