12 struct Depot;

    13 struct Waypoint;

    14 struct Station;

    15 struct ViewPort;

    16 struct NewsItem;

    17 struct DrawPixelInfo;

    18 struct Group;

    19 typedef byte VehicleOrderID;  ///< The index of an order within its current vehicle (not pool related)

    21 typedef uint16 EngineID;

    23 

    24 typedef EngineID *EngineList; ///< engine list type placeholder acceptable for C code (see helpers.cpp)

    25 

    26 /* IDs used in Pools */

    27 typedef uint16 StationID;

    28 static const StationID INVALID_STATION = 0xFFFF;

    29 typedef uint16 RoadStopID;

    30 typedef uint16 DepotID;

    31 typedef uint16 WaypointID;

    32 typedef uint16 OrderID;

    33 typedef uint16 SignID;

    34 typedef uint16 GroupID;

    35 typedef uint16 EngineRenewID;

    36 typedef uint16 DestinationID;

    37 

    38 /* DestinationID must be at least as large as every these below, because it can

    39  * be any of them

    40  */

    41 assert_compile(sizeof(DestinationID) >= sizeof(DepotID));

    42 assert_compile(sizeof(DestinationID) >= sizeof(WaypointID));

    43 assert_compile(sizeof(DestinationID) >= sizeof(StationID));