(svn r26157) -Feature: [NewGRF] Vehicle variable 4D for determining the position within an articulated vehicle.

src/newgrf_engine.cpp

@@ -627,6 +627,17 @@ static uint32 VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *object,
 			if (!v->IsPrimaryVehicle()) return 0;
 			return v->GetCurrentMaxSpeed();
 
+		case 0x4D: // Position within articulated vehicle
+			if (!HasBit(v->grf_cache.cache_valid, NCVV_POSITION_IN_VEHICLE)) {
+				byte artic_before = 0;
+				for (const Vehicle *u = v; u->IsArticulatedPart(); u = u->Previous()) artic_before++;
+				byte artic_after = 0;
+				for (const Vehicle *u = v; u->HasArticulatedPart(); u = u->Next()) artic_after++;
+				v->grf_cache.position_in_vehicle = artic_before | artic_after << 8;
+				SetBit(v->grf_cache.cache_valid, NCVV_POSITION_IN_VEHICLE);
+			}
+			return v->grf_cache.position_in_vehicle;
+
 		/* Variables which use the parameter */
 		case 0x60: // Count consist's engine ID occurrence
 			if (v->type != VEH_TRAIN) return v->GetEngine()->grf_prop.local_id == parameter ? 1 : 0;
@@ -1293,6 +1304,7 @@ void FillNewGRFVehicleCache(const Vehicle *v)
 		{ 0x41, NCVV_POSITION_SAME_ID_LENGTH },
 		{ 0x42, NCVV_CONSIST_CARGO_INFORMATION },
 		{ 0x43, NCVV_COMPANY_INFORMATION },
+		{ 0x4D, NCVV_POSITION_IN_VEHICLE },
 	};
 	assert_compile(NCVV_END == lengthof(cache_entries));
 

src/vehicle_base.h

@@ -58,6 +58,7 @@ enum NewGRFCacheValidValues {
 	NCVV_POSITION_SAME_ID_LENGTH   = 1, ///< This bit will be set if the NewGRF var 41 currently stored is valid.
 	NCVV_CONSIST_CARGO_INFORMATION = 2, ///< This bit will be set if the NewGRF var 42 currently stored is valid.
 	NCVV_COMPANY_INFORMATION       = 3, ///< This bit will be set if the NewGRF var 43 currently stored is valid.
+	NCVV_POSITION_IN_VEHICLE       = 4, ///< This bit will be set if the NewGRF var 4D currently stored is valid.
 	NCVV_END,                           ///< End of the bits.
 };
 
@@ -68,6 +69,7 @@ struct NewGRFCache {
 	uint32 position_same_id_length;   ///< Cache for NewGRF var 41.
 	uint32 consist_cargo_information; ///< Cache for NewGRF var 42. (Note: The cargotype is untranslated in the cache because the accessing GRF is yet unknown.)
 	uint32 company_information;       ///< Cache for NewGRF var 43.
+	uint32 position_in_vehicle;       ///< Cache for NewGRF var 4D.
 	uint8  cache_valid;               ///< Bitset that indicates which cache values are valid.
 };