(svn r11870) -Fix: slow down train when approaching tile we can't enter in more cases

(tunnel/bridge/depot from wrong direction, competitor's track, wrong railtype)
-Fix: do not make crossing red when we can't enter it in any case

src/train_cmd.cpp

@@ -3250,14 +3250,59 @@ static const byte _breakdown_speeds[16] = {
 	225, 210, 195, 180, 165, 150, 135, 120, 105, 90, 75, 60, 45, 30, 15, 15
 };
 
+
+/**
+ * Train is approaching line end, slow down and possibly reverse
+ *
+ * @param v front train engine
+ * @param signal not line end, just a red signal
+ * @return true iff we did NOT have to reverse
+ */
+static bool TrainApproachingLineEnd(Vehicle *v, bool signal)
+{
+	/* Calc position within the current tile */
+	uint x = v->x_pos & 0xF;
+	uint y = v->y_pos & 0xF;
+
+	switch (v->direction) {
+		case DIR_N : x = ~x + ~y + 24; break;
+		case DIR_NW: x = y;            /* FALLTHROUGH */
+		case DIR_NE: x = ~x + 16;      break;
+		case DIR_E : x = ~x + y + 8;   break;
+		case DIR_SE: x = y;            break;
+		case DIR_S : x = x + y - 8;    break;
+		case DIR_W : x = ~y + x + 8;   break;
+		default: break;
+	}
+
+	/* do not reverse when approaching red signal */
+	if (!signal && x + 4 >= TILE_SIZE) {
+		/* we are too near the tile end, reverse now */
+		v->cur_speed = 0;
+		ReverseTrainDirection(v);
+		return false;
+	}
+
+	/* slow down */
+	v->vehstatus |= VS_TRAIN_SLOWING;
+	uint16 break_speed = _breakdown_speeds[x & 0xF];
+	if (!(v->direction & 1)) break_speed >>= 1;
+	if (break_speed < v->cur_speed) v->cur_speed = break_speed;
+
+	return true;
+}
+
+
 /**
  * Checks for line end. Also, bars crossing at next tile if needed
  *
  * @param v vehicle we are checking
- * @return true iff we do NOT have to reverse
+ * @return true iff we did NOT have to reverse
  */
 static bool TrainCheckIfLineEnds(Vehicle *v)
 {
+	/* First, handle broken down train */
+
 	int t = v->breakdown_ctr;
 	if (t > 1) {
 		v->vehstatus |= VS_TRAIN_SLOWING;
@@ -3268,17 +3313,19 @@ static bool TrainCheckIfLineEnds(Vehicle *v)
 		v->vehstatus &= ~VS_TRAIN_SLOWING;
 	}
 
-	if (v->u.rail.track == TRACK_BIT_WORMHOLE) return true; // exit if inside a tunnel
-	if (v->u.rail.track == TRACK_BIT_DEPOT) return true; // exit if inside a depot
+	/* Exit if inside a tunnel/bridge or a depot */
+	if (v->u.rail.track == TRACK_BIT_WORMHOLE || v->u.rail.track == TRACK_BIT_DEPOT) return true;
 
 	TileIndex tile = v->tile;
 
+	/* entering a tunnel/bridge? */
 	if (IsTileType(tile, MP_TUNNELBRIDGE)) {
 		DiagDirection dir = GetTunnelBridgeDirection(tile);
 		if (DiagDirToDir(dir) == v->direction) return true;
 	}
 
-	if (IsTileType(tile, MP_RAILWAY) && GetRailTileType(tile) == RAIL_TILE_DEPOT) {
+	/* entering a depot? */
+	if (IsTileDepotType(tile, TRANSPORT_RAIL)) {
 		DiagDirection dir = ReverseDiagDir(GetRailDepotDirection(tile));
 		if (DiagDirToDir(dir) == v->direction) return true;
 	}
@@ -3287,61 +3334,34 @@ static bool TrainCheckIfLineEnds(Vehicle *v)
 	DiagDirection dir = TrainExitDir(v->direction, v->u.rail.track);
 	/* Calculate next tile */
 	tile += TileOffsByDiagDir(dir);
-	// determine the track status on the next tile.
+
+	/* Determine the track status on the next tile */
 	uint32 ts = GetTileTrackStatus(tile, TRANSPORT_RAIL, 0) & _reachable_tracks[dir];
 
-	/* Calc position within the current tile ?? */
-	uint x = v->x_pos & 0xF;
-	uint y = v->y_pos & 0xF;
+	/* We are sure the train is not entering a depot, it is detected above */
 
-	switch (v->direction) {
-		case DIR_N : x = ~x + ~y + 24; break;
-		case DIR_NW: x = y;            /* FALLTHROUGH */
-		case DIR_NE: x = ~x + 16;      break;
-		case DIR_E : x = ~x + y + 8;   break;
-		case DIR_SE: x = y;            break;
-		case DIR_S : x = x + y - 8;    break;
-		case DIR_W : x = ~y + x + 8;   break;
-		default: break;
+	/* no suitable trackbits at all || wrong railtype || not our track ||
+	 *   tunnel/bridge from opposite side || depot from opposite side */
+	if (GB(ts, 0, 16) == 0 || !CheckCompatibleRail(v, tile) || GetTileOwner(tile) != v->owner ||
+			(IsTileType(tile, MP_TUNNELBRIDGE) && GetTunnelBridgeDirection(tile) != dir) ||
+			(IsTileDepotType(tile, TRANSPORT_RAIL) && GetRailDepotDirection(tile) == dir) ) {
+		return TrainApproachingLineEnd(v, false);
 	}
 
-	if (GB(ts, 0, 16) != 0) {
-		/* If we approach a rail-piece which we can't enter, or the back of a depot, don't enter it! */
-		if (x + 4 >= TILE_SIZE &&
-				(!CheckCompatibleRail(v, tile) ||
-				(IsTileDepotType(tile, TRANSPORT_RAIL) &&
-				GetRailDepotDirection(tile) == dir))) {
-			v->cur_speed = 0;
-			ReverseTrainDirection(v);
-			return false;
-		}
-		if ((ts &= (ts >> 16)) == 0) {
-			/* make a rail/road crossing red
-			 * do not make crossing red behind depot the train is entering */
-			if (IsLevelCrossingTile(tile) && (!IsTileDepotType(v->tile, TRANSPORT_RAIL) || GetRailDepotDirection(v->tile) == dir)) {
-				if (!IsCrossingBarred(tile)) {
-					BarCrossing(tile);
-					SndPlayVehicleFx(SND_0E_LEVEL_CROSSING, v);
-					MarkTileDirtyByTile(tile);
-				}
-			}
-			return true;
-		}
-	} else if (x + 4 >= TILE_SIZE) {
-		v->cur_speed = 0;
-		ReverseTrainDirection(v);
-		return false;
-	}
+	/* approaching red signal */
+	if ((ts & (ts >> 16)) != 0) return TrainApproachingLineEnd(v, true);
 
-	/* slow down */
-	v->vehstatus |= VS_TRAIN_SLOWING;
-	uint16 break_speed = _breakdown_speeds[x & 0xF];
-	if (!(v->direction & 1)) break_speed >>= 1;
-	if (break_speed < v->cur_speed) v->cur_speed = break_speed;
+	/* approaching a rail/road crossing? then make it red */
+	if (IsLevelCrossingTile(tile) && !IsCrossingBarred(tile)) {
+		BarCrossing(tile);
+		SndPlayVehicleFx(SND_0E_LEVEL_CROSSING, v);
+		MarkTileDirtyByTile(tile);
+	}
 
 	return true;
 }
 
+
 static void TrainLocoHandler(Vehicle *v, bool mode)
 {
 	/* train has crashed? */