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, 16 insertions, 0 deletions

diff --git a/advtrains/couple.lua b/advtrains/couple.lua
index 9474dcf..cbeb661 100644
--- a/advtrains/couple.lua
+++ b/advtrains/couple.lua
@@ -28,6 +28,20 @@ end
 advtrains.register_coupler_type("chain", attrans("Buffer and Chain Coupler"))
 advtrains.register_coupler_type("scharfenberg", attrans("Scharfenberg Coupler"))
 
+for _, name in pairs {"couple", "decouple"} do
+	local t = {}
+	local function reg(f)
+		table.insert(t, f)
+	end
+	local function cb(...)
+		for _, f in ipairs(t) do
+			f(...)
+		end
+	end
+	advtrains["te_registered_on_" .. name] = t
+	advtrains["te_register_on_" .. name] = reg
+	advtrains["te_run_callbacks_on_" .. name] = cb
+end
 
 local function create_couple_entity(pos, train1, t1_is_front, train2, t2_is_front)
 	local id1 = train1.id
@@ -235,6 +249,8 @@ function advtrains.couple_trains(init_train, invert_init_train, stat_train, stat
 		return
 	end
 
+	advtrains.te_run_callbacks_on_couple(init_train, stat_train)
+
 	if stat_train_opposite then
 		-- insert wagons in inverse order and set their wagon_flipped state
 		for i=1,stat_wagoncnt do