* <h2>Basics</h2>

 *

 * <h3>Tile Types</h3>

 *

 * We have two different types of tiles in the drawing code:

 * Normal Railway Tiles (NRTs) which can have more than one track on it, and

 * Special Railways tiles (SRTs) which have only one track (like crossings, depots

 * stations, etc).

 *

 * <h3>Location Categories</h3>

 *

 * All tiles are categorized into three location groups (TLG):

 * Group 0: Tiles with both an even X coordinate and an even Y coordinate

 * Group 1: Tiles with an even X and an odd Y coordinate

 * Group 2: Tiles with an odd X and an even Y coordinate

 * Group 3: Tiles with both an odd X and Y coordnate.

 *

 * <h3>Pylon Points</h3>

 * <h4>Control Points</h4>

 * A Pylon Control Point (PCP) is a position where a wire (or rather two)

 * is mounted onto a pylon.

 * Each NRT does contain 4 PCPs which are bitmapped to a byte

 * variable and are represented by the DiagDirection enum

 *

 * Each track ends on two PCPs and thus requires one pylon on each end. However,

 * there is one exception: Straight-and-level tracks only have one pylon every

 * other tile.

 *

 * Now on each edge there are two PCPs: One from each adjacent tile. Both PCPs

 * are merged using an OR operation (i. e. if one tile needs a PCP at the postion

 * in question, both tiles get it).

 *

 * <h4>Position Points</h4>

 * A Pylon Position Point (PPP) is a position where a pylon is located on the

 * ground.  Each PCP owns 8 in (45 degree steps) PPPs that are located around

 * it. PPPs are represented using the Direction enum. Each track bit has PPPs

 * that are impossible (because the pylon would be situated on the track) and

 * some that are preferred (because the pylon would be rectangular to the track).

 *

 * <img src="../../elrail_tile.png">

 * <img src="../../elrail_track.png">

 *

 */

#include "stdafx.h"

#include "openttd.h"

#include "station_map.h"

#include "viewport_func.h"

#include "landscape.h"

#include "train.h"

#include "rail_gui.h"

#include "tunnelbridge_map.h"

#include "vehicle_func.h"

#include "tunnelbridge.h"

#include "elrail_func.h"

#include "engine_base.h"

#include "table/sprites.h"

#include "table/elrail_data.h"

static inline TLG GetTLG(TileIndex t)

{

	return (TLG)((HasBit(TileX(t), 0) << 1) + HasBit(TileY(t), 0));

}

/**

 * Finds which Electrified Rail Bits are present on a given tile.

 * @param t tile to check

 * @param override pointer to PCP override, can be NULL

 * @return trackbits of tile if it is electrified

 */

static TrackBits GetRailTrackBitsUniversal(TileIndex t, byte *override)

{

	switch (GetTileType(t)) {

		case MP_RAILWAY:

			if (!HasCatenary(GetRailType(t))) return TRACK_BIT_NONE;

			switch (GetRailTileType(t)) {

				case RAIL_TILE_NORMAL: case RAIL_TILE_SIGNALS:

					return GetTrackBits(t);

				case RAIL_TILE_WAYPOINT:

					return GetRailWaypointBits(t);

				default:

					return TRACK_BIT_NONE;

			}

			break;

		case MP_TUNNELBRIDGE:

			if (!HasCatenary(GetRailType(t))) return TRACK_BIT_NONE;

			if (override != NULL && (IsTunnel(t) || GetTunnelBridgeLength(t, GetOtherBridgeEnd(t)) > 0)) {

				*override = 1 << GetTunnelBridgeDirection(t);

			}

			return DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t));

		case MP_ROAD:

			if (!IsLevelCrossing(t)) return TRACK_BIT_NONE;

			if (!HasCatenary(GetRailType(t))) return TRACK_BIT_NONE;

			return GetCrossingRailBits(t);

		case MP_STATION:

			if (!IsRailwayStation(t)) return TRACK_BIT_NONE;

			if (!HasCatenary(GetRailType(t))) return TRACK_BIT_NONE;

			if (!IsStationTileElectrifiable(t)) return TRACK_BIT_NONE;