GRF loading stages:

  The stages are processed after each other. All GRFs are processed for the same stage before advancing.

 

  # Initialiation stage

  for newgrf in configured_newgrfs:

     # Each NewGRF peforms checks on its own wrt. its parameters and general game variables (like climate).

     if newgrf.is_happy_with_parameters():

        # Shout out "hello" to other GRFs.

     else:

        # disable newgrf

 

  # Reservation stage

  for newgrf in configured_newgrfs:

     # Each NewGRF may check what other GRFs called "hello", and may choose to leave the room if they don't like them,

     # and the other one did not leave again on its own.

     if newgrf.is_happy_with_other_grfs():

        # Make promises what this NewGRF provides wrt. shared items, like cargo and railtype definitions.

        newgrf.provide_cargos()

        newgrf.provide_railtypes()

     else:

        # disable newgrf

 

  # Activation stage

  for newgrf in configured_newgrfs:

     # Each NewGRF provides all the stuff, sometimes depending on what cargos and railtypes were promised by other GRFs.

     # Erroring out here is considered rude.

     newgrf.provide_stuff(available_cargotypes, available_railtypes)