Codechange: Restrict docking points of docks.

src/ship_cmd.cpp

@@ -612,7 +612,7 @@ bool IsShipDestinationTile(TileIndex tile, StationID station)
 	for (DiagDirection d = DIAGDIR_BEGIN; d != DIAGDIR_END; d++) {
 		TileIndex t = tile + TileOffsByDiagDir(d);
 		if (!IsValidTile(t)) continue;
-		if (IsDockTile(t) && GetStationIndex(t) == station) return true;
+		if (IsDockTile(t) && GetStationIndex(t) == station && IsValidDockingDirectionForDock(t, d)) return true;
 		if (IsTileType(t, MP_INDUSTRY)) {
 			const Industry *i = Industry::GetByTile(t);
 			if (i->neutral_station != nullptr && i->neutral_station->index == station) return true;

src/station_cmd.cpp

@@ -2631,6 +2631,28 @@ void ClearDockingTilesCheckingNeighbours(TileIndex tile)
 	}
 }
 
+/**
+ * Check if a dock tile can be docked from the given direction.
+ * @param t Tile index of dock.
+ * @param d DiagDirection adjacent to dock being tested.
+ * @return True iff the dock can be docked from the given direction.
+ */
+bool IsValidDockingDirectionForDock(TileIndex t, DiagDirection d)
+{
+	assert(IsDockTile(t));
+
+	/** Bitmap of valid directions for each dock tile part. */
+	static const uint8 _valid_docking_tile[] = {
+		0, 0, 0, 0,                        // No docking against the slope part.
+		1 << DIAGDIR_NE | 1 << DIAGDIR_SW, // Docking permitted at the end
+		1 << DIAGDIR_NW | 1 << DIAGDIR_SE, // of the flat piers.
+	};
+
+	StationGfx gfx = GetStationGfx(t);
+	assert(gfx < lengthof(_valid_docking_tile));
+	return HasBit(_valid_docking_tile[gfx], d);
+}
+
 /**
  * Find the part of a dock that is land-based
  * @param t Dock tile to find land part of

src/station_func.h

@@ -43,6 +43,7 @@ void DeleteOilRig(TileIndex t);
 void UpdateStationDockingTiles(Station *st);
 void RemoveDockingTile(TileIndex t);
 void ClearDockingTilesCheckingNeighbours(TileIndex tile);
+bool IsValidDockingDirectionForDock(TileIndex t, DiagDirection d);
 
 /* Check if a rail station tile is traversable. */
 bool IsStationTileBlocked(TileIndex tile);

src/water_cmd.cpp

@@ -187,7 +187,7 @@ void CheckForDockingTile(TileIndex t)
 		TileIndex tile = t + TileOffsByDiagDir(d);
 		if (!IsValidTile(tile)) continue;
 
-		if (IsDockTile(tile)) {
+		if (IsDockTile(tile) && IsValidDockingDirectionForDock(tile, d)) {
 			Station::GetByTile(tile)->docking_station.Add(t);
 			SetDockingTile(t, true);
 		}