(svn r5283) -Backport: r5260

-Fix: It was possible to convert the railtype of a bridge while a train was on it

slope.h

@@ -0,0 +1,30 @@
+/* $Id$ */
+
+#ifndef SLOPE_H
+#define SLOPE_H
+
+typedef enum Slope {
+	SLOPE_FLAT  = 0x00,
+	SLOPE_W     = 0x01,
+	SLOPE_S     = 0x02,
+	SLOPE_E     = 0x04,
+	SLOPE_N     = 0x08,
+	SLOPE_STEEP = 0x10,
+	SLOPE_NW = SLOPE_N | SLOPE_W,
+	SLOPE_SW = SLOPE_S | SLOPE_W,
+	SLOPE_SE = SLOPE_S | SLOPE_E,
+	SLOPE_NE = SLOPE_N | SLOPE_E,
+	SLOPE_EW = SLOPE_E | SLOPE_W,
+	SLOPE_NS = SLOPE_N | SLOPE_S,
+	SLOPE_ELEVATED = SLOPE_N | SLOPE_E | SLOPE_S | SLOPE_W,
+	SLOPE_NWS = SLOPE_N | SLOPE_W | SLOPE_S,
+	SLOPE_WSE = SLOPE_W | SLOPE_S | SLOPE_E,
+	SLOPE_SEN = SLOPE_S | SLOPE_E | SLOPE_N,
+	SLOPE_ENW = SLOPE_E | SLOPE_N | SLOPE_W,
+	SLOPE_STEEP_W = SLOPE_STEEP | SLOPE_NWS,
+	SLOPE_STEEP_S = SLOPE_STEEP | SLOPE_WSE,
+	SLOPE_STEEP_E = SLOPE_STEEP | SLOPE_SEN,
+	SLOPE_STEEP_N = SLOPE_STEEP | SLOPE_ENW
+} Slope;
+
+#endif

tunnelbridge_cmd.c

@@ -8,6 +8,7 @@
 #include "stdafx.h"
 #include "openttd.h"
 #include "bridge_map.h"
+#include "slope.h"
 #include "table/sprites.h"
 #include "table/strings.h"
 #include "functions.h"
@@ -713,6 +714,19 @@ static TileIndex FindEdgesOfBridge(TileIndex tile, TileIndex *endtile)
 	return start;
 }
 
+
+static uint GetBridgeHeightRamp(TileIndex t)
+{
+	/* Return the height there (the height of the NORTH CORNER)
+	 * If the end of the bridge is on a tile with all corners except the north corner raised,
+	 * the z coordinate is 1 height level too low. Compensate for that */
+	return
+		TilePixelHeight(t) +
+		(GetTileSlope(t, NULL) == SLOPE_WSE ? TILE_HEIGHT : 0) +
+		TILE_HEIGHT;
+}
+
+
 static int32 DoClearBridge(TileIndex tile, uint32 flags)
 {
 	TileIndex endtile;
@@ -898,16 +912,13 @@ int32 DoConvertTunnelBridgeRail(TileIndex tile, uint totype, bool exec)
 	} else if ((_m[tile].m5 & 0xC6) == 0x80) {
 		TileIndex starttile;
 		int32 cost;
-		uint z = TilePixelHeight(tile);
-
-		z += 8;
 
 		if (!CheckTileOwnership(tile)) return CMD_ERROR;
 
 		// railway bridge
 		starttile = tile = FindEdgesOfBridge(tile, &endtile);
 		// Make sure there's no vehicle on the bridge
-		v = FindVehicleBetween(tile, endtile, z);
+		v = FindVehicleBetween(tile, endtile, GetBridgeHeightRamp(tile));
 		if (v != NULL) {
 			VehicleInTheWayErrMsg(v);
 			return CMD_ERROR;