(svn r15521) -Codechange: add helper function to get the display tractive effort of a vehicle.

3 files changed, 19 insertions, 3 deletions

diff --git a/src/build_vehicle_gui.cpp b/src/build_vehicle_gui.cpp
index 9164d95b4..feb01a051 100644
--- a/src/build_vehicle_gui.cpp
+++ b/src/build_vehicle_gui.cpp
@@ -512,11 +512,10 @@ static int DrawRailWagonPurchaseInfo(int x, int y, EngineID engine_number, const
 static int DrawRailEnginePurchaseInfo(int x, int y, EngineID engine_number, const RailVehicleInfo *rvi)
 {
 	const Engine *e = GetEngine(engine_number);
-	uint weight = e->GetDisplayWeight();
 
 	/* Purchase Cost - Engine weight */
 	SetDParam(0, e->GetCost());
-	SetDParam(1, weight);
+	SetDParam(1, e->GetDisplayWeight());
 	DrawString(x, y, STR_PURCHASE_INFO_COST_WEIGHT, TC_FROMSTRING);
 	y += 10;
 
@@ -528,7 +527,7 @@ static int DrawRailEnginePurchaseInfo(int x, int y, EngineID engine_number, cons
 
 	/* Max tractive effort - not applicable if old acceleration or maglev */
 	if (_settings_game.vehicle.train_acceleration_model != TAM_ORIGINAL && rvi->railtype != RAILTYPE_MAGLEV) {
-		SetDParam(0, (weight * 10 * GetEngineProperty(engine_number, 0x1F, rvi->tractive_effort)) / 256);
+		SetDParam(0, e->GetDisplayMaxTractiveEffort());
 		DrawString(x, y, STR_PURCHASE_INFO_MAX_TE, TC_FROMSTRING);
 		y += 10;
 	}
diff --git a/src/engine.cpp b/src/engine.cpp
index 499ac399d..8373d9430 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -204,6 +204,22 @@ uint Engine::GetDisplayWeight() const
 	}
 }
 
+/**
+ * Returns the tractive effort for display purposes.
+ * For dual-headed train-engines this is the tractive effort of both heads
+ * @return tractive effort in display units kN
+ */
+uint Engine::GetDisplayMaxTractiveEffort() const
+{
+	/* Currently only trains have 'tractive effort' */
+	switch (this->type) {
+		case VEH_TRAIN:
+			return (10 * this->GetDisplayWeight() * GetEngineProperty(this->index, 0x1F, this->u.rail.tractive_effort)) / 256;
+
+		default: NOT_REACHED();
+	}
+}
+
 /** Sets cached values in Company::num_vehicles and Group::num_vehicles
  */
 void SetCachedEngineCounts()
diff --git a/src/engine_base.h b/src/engine_base.h
index 787ae804b..dbbb2c308 100644
--- a/src/engine_base.h
+++ b/src/engine_base.h
@@ -55,6 +55,7 @@ struct Engine : PoolItem<Engine, EngineID, &_Engine_pool> {
 	uint GetDisplayMaxSpeed() const;
 	uint GetPower() const;
 	uint GetDisplayWeight() const;
+	uint GetDisplayMaxTractiveEffort() const;
 };
 
 static inline bool IsEngineIndex(uint index)