This file deals with displaying wires and pylons for electric railways. More...

#include "stdafx.h"
#include "station_map.h"
#include "viewport_func.h"
#include "train.h"
#include "rail_gui.h"
#include "tunnelbridge_map.h"
#include "tunnelbridge.h"
#include "elrail_func.h"
#include "company_base.h"
#include "newgrf_railtype.h"
#include "table/elrail_data.h"
#include "safeguards.h"

Functions
static TileLocationGroup	GetTileLocationGroup (TileIndex t)
	Get the tile location group of a tile.
static TrackBits	GetRailTrackBitsUniversal (TileIndex t, DiagDirections *override)
	Finds which Electrified Rail Bits are present on a given tile.
static TrackBits	MaskWireBits (TileIndex t, TrackBits tracks)
	Masks out track bits when neighbouring tiles are unelectrified.
static SpriteID	GetWireBase (TileIndex tile, TileContext context=TCX_NORMAL)
	Get the base wire sprite to use.
static SpriteID	GetPylonBase (TileIndex tile, TileContext context=TCX_NORMAL)
	Get the base pylon sprite to use.
static void	AdjustTileh (TileIndex tile, Slope *tileh)
	Corrects the tileh for certain tile types.
static int	GetPCPElevation (TileIndex tile, DiagDirection pcp_pos)
	Returns the Z position of a Pylon Control Point.
void	DrawRailCatenaryOnTunnel (const TileInfo *ti)
	Draws wires on a tunnel tile.
static void	DrawRailCatenaryRailway (const TileInfo *ti)
	Draws wires and, if required, pylons on a given tile.
void	DrawRailCatenaryOnBridge (const TileInfo *ti)
	Draws wires on a tunnel tile.
void	DrawRailCatenary (const TileInfo *ti)
	Draws overhead wires and pylons for electric railways.
void	SettingsDisableElrail (int32_t new_value)
	Callback for changes to the electrified rails setting.
void	UpdateDisableElrailSettingState (bool disable, bool update_vehicles)

Detailed Description

This file deals with displaying wires and pylons for electric railways.

Basics

Tile Types

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).

Location Categories

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 coordinate.

Pylon Points

Control Points

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 position in question, both tiles get it).

Position Points

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).