Implement staticdata for trains

This patch exposes train.staticdata that can be used by other modders to
save data in trains across restarts. It additionally exposes two new
APIs for modders where this is relevant:

* advtrains.te_register_on_couple(function(init_train, stat_train)):
  registers a callback for train coupling, where stat_train is couple
  into init_train and is subsequently removed. This callback is run
  before the actual coupling takes place; in particular, it is run
  before stat_train is removed.
* advtrains.te_register_on_decouple(function(train, newtrain, index)):
  registers a callback for train decoupling, where newtrain is created
  by splitting the train at the given index (the wagon at the index is
  part of the new train). This callback is run after decoupling takes
  place.

advtrains.te_register_on_decouple(function

1 files changed, 6 insertions, 0 deletions

diff --git a/advtrains/trainlogic.lua b/advtrains/trainlogic.lua
index 3b006d2..ed49a4c 100644
--- a/advtrains/trainlogic.lua
+++ b/advtrains/trainlogic.lua
@@ -263,6 +263,10 @@ function advtrains.train_ensure_init(id, train)
 		atwarn(debug.traceback())
 		return nil
 	end
+
+	if not train.staticdata then
+		train.staticdata = {}
+	end
 	
 	train.dirty = true
 	if train.no_step then
@@ -1190,6 +1194,8 @@ function advtrains.split_train_at_index(train, index)
 	newtrain.points_split = advtrains.merge_tables(train.points_split)
 	newtrain.autocouple = train.autocouple
 
+	advtrains.te_run_callbacks_on_decouple(train, newtrain, index)
+
 	return newtrain_id -- return new train ID, so new train can be manipulated
 
 end