(svn r3403) -Codechange: [multiheaded engines] the references between the front and rear engines are no longer saved

	instead the pointers are generated on load

6 files changed, 162 insertions, 102 deletions

diff --git a/openttd.c b/openttd.c
index d84e73b18..28c97c3b5 100644
--- a/openttd.c
+++ b/openttd.c
@@ -40,6 +40,7 @@
 #include "depot.h"
 #include "waypoint.h"
 #include "ai/ai.h"
+#include "train.h"
 
 #include <stdarg.h>
 
@@ -1144,6 +1145,10 @@ bool AfterLoadGame(void)
 	 * subtype to the new format */
 	if (CheckSavegameVersionOldStyle(17, 1)) ConvertOldMultiheadToNew();
 
+	/* Connect front and rear engines of multiheaded trains
+		since this info were no longer saved in savegame version 20 */
+	if (!CheckSavegameVersion(20)) ConnectMultiheadedTrains();
+
 	// Update current year
 	SetDate(_date);
 
diff --git a/saveload.c b/saveload.c
index fb141cc91..386233160 100644
--- a/saveload.c
+++ b/saveload.c
@@ -29,7 +29,7 @@
 #include <setjmp.h>
 
 enum {
-	SAVEGAME_VERSION = 19,
+	SAVEGAME_VERSION = 20,
 
 };
 
diff --git a/train.h b/train.h
index 9cb3a78d2..8399e8cc2 100644
--- a/train.h
+++ b/train.h
@@ -205,4 +205,7 @@ static inline Vehicle *GetLastEnginePart(Vehicle *v)
 	return v;
 }
 
+void ConvertOldMultiheadToNew(void);
+void ConnectMultiheadedTrains(void);
+
 #endif /* TRAIN_H */
diff --git a/train_cmd.c b/train_cmd.c
index f1f444252..424e53b5a 100644
--- a/train_cmd.c
+++ b/train_cmd.c
@@ -3700,3 +3700,155 @@ void InitializeTrains(void)
 {
 	_age_cargo_skip_counter = 1;
 }
+
+/*
+ * Link front and rear multiheaded engines to each other
+ * This is done when loading a savegame
+ */
+void ConnectMultiheadedTrains(void)
+{
+	Vehicle *v;
+
+	FOR_ALL_VEHICLES(v) {
+		if (v->type == VEH_Train) {
+			v->u.rail.other_multiheaded_part = NULL;
+		}
+	}
+
+	FOR_ALL_VEHICLES(v) {
+		if (v->type == VEH_Train && IsFrontEngine(v)) {
+			Vehicle *u = v;
+
+			BEGIN_ENUM_WAGONS(u) {
+				if (u->u.rail.other_multiheaded_part != NULL) continue; // we already linked this one
+
+				if (IsMultiheaded(u)) {
+					if (!IsTrainEngine(u)) {
+						/* we got a rear car without a front car. We will convert it to a front one */
+						SetTrainEngine(u);
+						u->spritenum--;
+					}
+
+					{
+						Vehicle *w;
+
+						for(w = u->next; w != NULL && (w->engine_type != u->engine_type || w->u.rail.other_multiheaded_part != NULL); w = GetNextVehicle(w));
+						if (w != NULL) {
+							/* we found a car to partner with this engine. Now we will make sure it face the right way */
+							if (IsTrainEngine(w)) {
+								ClearTrainEngine(w);
+								w->spritenum++;
+							}
+						}
+
+						if (w != NULL) {
+							w->u.rail.other_multiheaded_part = u;
+							u->u.rail.other_multiheaded_part = w;
+						} else {
+							/* we got a front car and no rear cars. We will fake this one for forget that it should have been multiheaded */
+							ClearMultiheaded(u);
+						}
+					}
+				}
+			} END_ENUM_WAGONS(u)
+		}
+	}
+}
+
+/*
+ *  Converts all trains to the new subtype format introduced in savegame 16.2
+ *  It also links multiheaded engines or make them forget they are multiheaded if no suitable partner is found
+ */
+void ConvertOldMultiheadToNew(void)
+{
+	Vehicle *v;
+	FOR_ALL_VEHICLES(v) {
+		if (v->type == VEH_Train) {
+			SETBIT(v->subtype, 7);	// indicates that it's the old format and needs to be converted in the next loop
+		}
+	}
+
+	FOR_ALL_VEHICLES(v) {
+		if (v->type == VEH_Train) {
+			if (HASBIT(v->subtype, 7) && ((v->subtype & ~0x80) == 0 || (v->subtype & ~0x80) == 4)) {
+				Vehicle *u = v;
+
+				BEGIN_ENUM_WAGONS(u)
+					const RailVehicleInfo *rvi = RailVehInfo(u->engine_type);
+				CLRBIT(u->subtype, 7);
+				switch (u->subtype) {
+					case 0:	/* TS_Front_Engine */
+						if (rvi->flags & RVI_MULTIHEAD) {
+							SetMultiheaded(u);
+						}
+						SetFrontEngine(u);
+						SetTrainEngine(u);
+						break;
+					case 1:	/* TS_Artic_Part */
+						u->subtype = 0;
+						SetArticulatedPart(u);
+						break;
+					case 2:	/* TS_Not_First */
+						u->subtype = 0;
+						if (rvi->flags & RVI_WAGON) {
+							// normal wagon
+							SetTrainWagon(u);
+							break;
+						}
+							if (rvi->flags & RVI_MULTIHEAD && rvi->image_index == u->spritenum - 1) {
+								// rear end of a multiheaded engine
+								SetMultiheaded(u);
+								break;
+							}
+							if (rvi->flags & RVI_MULTIHEAD) {
+								SetMultiheaded(u);
+							}
+							SetTrainEngine(u);
+						break;
+					case 4:	/* TS_Free_Car */
+						u->subtype = 0;
+						SetTrainWagon(u);
+						SetFreeWagon(u);
+						break;
+					default: NOT_REACHED(); break;
+				}
+				END_ENUM_WAGONS(u)
+					u = v;
+				BEGIN_ENUM_WAGONS(u)
+					const RailVehicleInfo *rvi = RailVehInfo(u->engine_type);
+
+				if (u->u.rail.other_multiheaded_part != NULL) continue;
+
+				if (rvi->flags & RVI_MULTIHEAD) {
+					if (!IsTrainEngine(u)) {
+						/* we got a rear car without a front car. We will convert it to a front one */
+						SetTrainEngine(u);
+						u->spritenum--;
+					}
+
+					{
+						Vehicle *w;
+
+						for(w = u->next; w != NULL && (w->engine_type != u->engine_type || w->u.rail.other_multiheaded_part != NULL); w = GetNextVehicle(w));
+						if (w != NULL) {
+							/* we found a car to partner with this engine. Now we will make sure it face the right way */
+							if (IsTrainEngine(w)) {
+								ClearTrainEngine(w);
+								w->spritenum++;
+							}
+						}
+
+						if (w != NULL) {
+							w->u.rail.other_multiheaded_part = u;
+							u->u.rail.other_multiheaded_part = w;
+						} else {
+							/* we got a front car and no rear cars. We will fake this one for forget that it should have been multiheaded */
+							ClearMultiheaded(u);
+						}
+					}
+				}
+				END_ENUM_WAGONS(u)
+			}
+		}
+	}
+}
diff --git a/vehicle.c b/vehicle.c
index b7fa42aee..8e3111552 100644
--- a/vehicle.c
+++ b/vehicle.c
@@ -2128,7 +2128,7 @@ static const SaveLoad _train_desc[] = {
 
 	SLE_CONDARR(NullStruct, null, SLE_FILE_U8 | SLE_VAR_NULL, 2, 2, 255),
 
-	SLE_CONDREFX(offsetof(Vehicle,u)+offsetof(VehicleRail,other_multiheaded_part), REF_VEHICLE, 2, 255),	// added with 17.1, but was blank since 2
+	SLE_CONDREFX(offsetof(Vehicle,u)+offsetof(VehicleRail,other_multiheaded_part), REF_VEHICLE, 2, 19),	// added with 17.1, but was blank since 2. Removed in 20
 	// reserve extra space in savegame here. (currently 3 bytes)
 	SLE_CONDARR(NullStruct,null,SLE_FILE_U8 | SLE_VAR_NULL, 3, 2, 255),
 
@@ -2282,105 +2282,6 @@ static void Save_VEHS(void)
 	}
 }
 
-/*
- *  Converts all trains to the new subtype format introduced in savegame 16.2
- *  It also links multiheaded engines or make them forget they are multiheaded if no suitable partner is found
- */
-void ConvertOldMultiheadToNew(void)
-{
-	Vehicle *v;
-	FOR_ALL_VEHICLES(v) {
-		if (v->type == VEH_Train) {
-			v->u.rail.other_multiheaded_part = NULL;
-			SETBIT(v->subtype, 7);	// indicates that it's the old format and needs to be converted in the next loop
-		}
-	}
-
-	FOR_ALL_VEHICLES(v) {
-		if (v->type == VEH_Train) {
-			if (HASBIT(v->subtype, 7) && ((v->subtype & ~0x80) == 0 || (v->subtype & ~0x80) == 4)) {
-				Vehicle *u = v;
-
-				BEGIN_ENUM_WAGONS(u)
-					const RailVehicleInfo *rvi = RailVehInfo(u->engine_type);
-				CLRBIT(u->subtype, 7);
-				switch (u->subtype) {
-					case 0:	/* TS_Front_Engine */
-						if (rvi->flags & RVI_MULTIHEAD) {
-							SetMultiheaded(u);
-						}
-						SetFrontEngine(u);
-						SetTrainEngine(u);
-						break;
-					case 1:	/* TS_Artic_Part */
-						u->subtype = 0;
-						SetArticulatedPart(u);
-						break;
-					case 2:	/* TS_Not_First */
-						u->subtype = 0;
-						if (rvi->flags & RVI_WAGON) {
-							// normal wagon
-							SetTrainWagon(u);
-							break;
-						}
-							if (rvi->flags & RVI_MULTIHEAD && rvi->image_index == u->spritenum - 1) {
-								// rear end of a multiheaded engine
-								SetMultiheaded(u);
-								break;
-							}
-							if (rvi->flags & RVI_MULTIHEAD) {
-								SetMultiheaded(u);
-							}
-							SetTrainEngine(u);
-						break;
-					case 4:	/* TS_Free_Car */
-						u->subtype = 0;
-						SetTrainWagon(u);
-						SetFreeWagon(u);
-						break;
-					default: NOT_REACHED(); break;
-				}
-				END_ENUM_WAGONS(u)
-					u = v;
-				BEGIN_ENUM_WAGONS(u)
-					const RailVehicleInfo *rvi = RailVehInfo(u->engine_type);
-
-				if (u->u.rail.other_multiheaded_part != NULL) continue;
-
-				if (rvi->flags & RVI_MULTIHEAD) {
-					if (!IsTrainEngine(u)) {
-						/* we got a rear car without a front car. We will convert it to a front one */
-						SetTrainEngine(u);
-						u->spritenum--;
-					}
-
-					{
-						Vehicle *w;
-
-						for(w = u->next; w != NULL && (w->engine_type != u->engine_type || w->u.rail.other_multiheaded_part != NULL); w = GetNextVehicle(w));
-						if (w != NULL) {
-							/* we found a car to partner with this engine. Now we will make sure it face the right way */
-							if (IsTrainEngine(w)) {
-								ClearTrainEngine(w);
-								w->spritenum++;
-							}
-						}
-
-						if (w != NULL) {
-							w->u.rail.other_multiheaded_part = u;
-							u->u.rail.other_multiheaded_part = w;
-						} else {
-							/* we got a front car and no rear cars. We will fake this one for forget that it should have been multiheaded */
-							ClearMultiheaded(u);
-						}
-					}
-				}
-				END_ENUM_WAGONS(u)
-			}
-		}
-	}
-}
-
 // Will be called when vehicles need to be loaded.
 static void Load_VEHS(void)
 {
diff --git a/vehicle.h b/vehicle.h
index c00f0b8da..7136ed172 100644
--- a/vehicle.h
+++ b/vehicle.h
@@ -313,7 +313,6 @@ int32 GetTrainRunningCost(const Vehicle *v);
 int CheckTrainStoppedInDepot(const Vehicle *v);
 
 bool VehicleNeedsService(const Vehicle *v);
-void ConvertOldMultiheadToNew(void);
 
 typedef struct GetNewVehiclePosResult {
 	int x,y;