elrail.cpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

 
#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"

static inline TileLocationGroup GetTileLocationGroup(TileIndex t)
{
  return static_cast<TileLocationGroup>((GB(TileX(t), 0, 1) << 1) + GB(TileY(t), 0, 1));
}

static TrackBits GetRailTrackBitsUniversal(TileIndex t, DiagDirections *override)
{
  switch (GetTileType(t)) {
    case TileType::Railway:
      if (!HasRailCatenary(GetRailType(t))) return TRACK_BIT_NONE;
      switch (GetRailTileType(t)) {
        case RailTileType::Normal: case RailTileType::Signals:
          return GetTrackBits(t);
        default:
          return TRACK_BIT_NONE;
      }
      break;
 
    case TileType::TunnelBridge:
      if (GetTunnelBridgeTransportType(t) != TRANSPORT_RAIL) return TRACK_BIT_NONE;
      if (!HasRailCatenary(GetRailType(t))) return TRACK_BIT_NONE;
      if (override != nullptr && (IsTunnel(t) || GetTunnelBridgeLength(t, GetOtherBridgeEnd(t)) > 0)) {
        *override = GetTunnelBridgeDirection(t);
      }
      return DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t));
 
    case TileType::Road:
      if (!IsLevelCrossing(t)) return TRACK_BIT_NONE;
      if (!HasRailCatenary(GetRailType(t))) return TRACK_BIT_NONE;
      return GetCrossingRailBits(t);
 
    case TileType::Station:
      if (!HasStationRail(t)) return TRACK_BIT_NONE;
      if (!HasRailCatenary(GetRailType(t))) return TRACK_BIT_NONE;
      return TrackToTrackBits(GetRailStationTrack(t));
 
    default:
      return TRACK_BIT_NONE;
  }
}

static TrackBits MaskWireBits(TileIndex t, TrackBits tracks)
{
  /* Single track bits are never masked out. */
  if (HasAtMostOneBit(tracks)) [[likely]] return tracks;
 
  if (!IsPlainRailTile(t)) return tracks;
 
  TrackdirBits neighbour_tdb = TRACKDIR_BIT_NONE;
  for (DiagDirection d = DiagDirection::Begin; d < DiagDirection::End; d++) {
    /* If the neighbour tile is either not electrified or has no tracks that can be reached
     * from this tile, mark all trackdirs that can be reached from the neighbour tile
     * as needing no catenary. We make an exception for blocked station tiles with a matching
     * axis that still display wires to preserve visual continuity. */
    TileIndex next_tile = TileAddByDiagDir(t, d);
    RailType rt = GetTileRailType(next_tile);
    if (rt == INVALID_RAILTYPE || !HasRailCatenary(rt) ||
        ((TrackdirBitsToTrackBits(GetTileTrackStatus(next_tile, TRANSPORT_RAIL, RoadTramType::Invalid).trackdirs) & DiagdirReachesTracks(d)) == TRACK_BIT_NONE &&
        (!HasStationTileRail(next_tile) || GetRailStationAxis(next_tile) != DiagDirToAxis(d) || !CanStationTileHaveWires(next_tile)))) {
      neighbour_tdb |= DiagdirReachesTrackdirs(ReverseDiagDir(d));
    }
  }
 
  /* If the tracks from either a diagonal crossing or don't overlap, both
   * trackdirs have to be marked to mask the corresponding track bit. Else
   * one marked trackdir is enough the mask the track bit. */
  TrackBits mask;
  if (tracks == TRACK_BIT_CROSS || !TracksOverlap(tracks)) {
    /* If the tracks form either a diagonal crossing or don't overlap, both
     * trackdirs have to be marked to mask the corresponding track bit. */
    mask = ~(TrackBits)((neighbour_tdb & (neighbour_tdb >> 8)) & TRACK_BIT_MASK);
    /* If that results in no masked tracks and it is not a diagonal crossing,
     * require only one marked trackdir to mask. */
    if (tracks != TRACK_BIT_CROSS && (mask & TRACK_BIT_MASK) == TRACK_BIT_MASK) mask = ~TrackdirBitsToTrackBits(neighbour_tdb);
  } else {
    /* Require only one marked trackdir to mask the track. */
    mask = ~TrackdirBitsToTrackBits(neighbour_tdb);
    /* If that results in an empty set, require both trackdirs for diagonal track. */
    if ((tracks & mask) == TRACK_BIT_NONE) {
      if ((neighbour_tdb & TRACKDIR_BIT_X_NE) == 0 || (neighbour_tdb & TRACKDIR_BIT_X_SW) == 0) mask |= TRACK_BIT_X;
      if ((neighbour_tdb & TRACKDIR_BIT_Y_NW) == 0 || (neighbour_tdb & TRACKDIR_BIT_Y_SE) == 0) mask |= TRACK_BIT_Y;
      /* If that still is not enough, require both trackdirs for any track. */
      if ((tracks & mask) == TRACK_BIT_NONE) mask = ~(TrackBits)((neighbour_tdb & (neighbour_tdb >> 8)) & TRACK_BIT_MASK);
    }
  }
 
  /* Mask the tracks only if at least one track bit would remain. */
  return (tracks & mask) != TRACK_BIT_NONE ? tracks & mask : tracks;
}

static inline SpriteID GetWireBase(TileIndex tile, TileContext context = TCX_NORMAL)
{
  const RailTypeInfo *rti = GetRailTypeInfo(GetRailType(tile));
  SpriteID wires = GetCustomRailSprite(rti, tile, RailSpriteType::Wires, context);
  return wires == 0 ? SPR_WIRE_BASE : wires;
}

static inline SpriteID GetPylonBase(TileIndex tile, TileContext context = TCX_NORMAL)
{
  const RailTypeInfo *rti = GetRailTypeInfo(GetRailType(tile));
  SpriteID pylons = GetCustomRailSprite(rti, tile, RailSpriteType::Pylons, context);
  return pylons == 0 ? SPR_PYLON_BASE : pylons;
}

static void AdjustTileh(TileIndex tile, Slope *tileh)
{
  if (IsTileType(tile, TileType::TunnelBridge)) {
    if (IsTunnel(tile)) {
      *tileh = SLOPE_STEEP; // XXX - Hack to make tunnel entrances to always have a pylon
    } else if (*tileh != SLOPE_FLAT) {
      *tileh = SLOPE_FLAT;
    } else {
      *tileh = InclinedSlope(GetTunnelBridgeDirection(tile));
    }
  }
}

static int GetPCPElevation(TileIndex tile, DiagDirection pcp_pos)
{
  /* The elevation of the "pylon"-sprite should be the elevation at the PCP.
   * PCPs are always on a tile edge.
   *
   * This position can be outside of the tile, i.e. ?_pcp_offset == TILE_SIZE > TILE_SIZE - 1.
   * So we have to move it inside the tile, because if the neighboured tile has a foundation,
   * that does not smoothly connect to the current tile, we will get a wrong elevation from GetSlopePixelZ().
   *
   * When we move the position inside the tile, we will get a wrong elevation if we have a slope.
   * To catch all cases we round the Z position to the next (TILE_HEIGHT / 2).
   * This will return the correct elevation for slopes and will also detect non-continuous elevation on edges.
   *
   * Also note that the result of GetSlopePixelZ() is very special on bridge-ramps.
   */
 
  int z = GetSlopePixelZ(TileX(tile) * TILE_SIZE + std::min<int8_t>(_x_pcp_offsets[pcp_pos], TILE_SIZE - 1),
                         TileY(tile) * TILE_SIZE + std::min<int8_t>(_y_pcp_offsets[pcp_pos], TILE_SIZE - 1), true);
  /* Round the Z to the nearest half tile height. */
  static const uint HALF_TILE_HEIGHT = TILE_HEIGHT / 2;
  return (z + HALF_TILE_HEIGHT / 2) / HALF_TILE_HEIGHT * HALF_TILE_HEIGHT;
}

void DrawRailCatenaryOnTunnel(const TileInfo *ti)
{
  DiagDirection dir = GetTunnelBridgeDirection(ti->tile);
 
  SpriteID wire_base = GetWireBase(ti->tile);
 
  const SortableSpriteStruct &sss = _rail_catenary_sprite_data_tunnel[dir];
  AddSortableSpriteToDraw(wire_base + sss.image_offset, PAL_NONE, ti->x, ti->y, GetTilePixelZ(ti->tile), sss, IsTransparencySet(TransparencyOption::Catenary));
}

static void DrawRailCatenaryRailway(const TileInfo *ti)
{
  /* Pylons are placed on a tile edge, so we need to take into account
   * the track configuration of 2 adjacent tiles. */
  EnumIndexArray<TrackBits, TileSource, TileSource::End> track_config;
  EnumIndexArray<TrackBits, TileSource, TileSource::End> wire_config;
  EnumIndexArray<bool, TileSource, TileSource::End> is_flat;
  /* Note that ti->tileh has already been adjusted for Foundations */
  EnumIndexArray<Slope, TileSource, TileSource::End> tileh{ti->tileh, SLOPE_FLAT};
 
  /* Half tile slopes coincide only with horizontal/vertical track.
   * Faking a flat slope results in the correct sprites on positions. */
  Corner halftile_corner = CORNER_INVALID;
  if (IsHalftileSlope(tileh[TileSource::Home])) {
    halftile_corner = GetHalftileSlopeCorner(tileh[TileSource::Home]);
    tileh[TileSource::Home] = SLOPE_FLAT;
  }
 
  TileLocationGroup tlg = GetTileLocationGroup(ti->tile);
  DiagDirections pcp_status{};
  DiagDirections override_pcp{};
  DiagDirectionIndexArray<Directions> ppp_preferred{};
  DiagDirectionIndexArray<Directions> ppp_allowed{};
 
  /* Find which rail bits are present, and select the override points.
   * We don't draw a pylon:
   * 1) INSIDE a tunnel (we wouldn't see it anyway)
   * 2) on the "far" end of a bridge head (the one that connects to bridge middle),
   *    because that one is drawn on the bridge. Exception is for length 0 bridges
   *    which have no middle tiles */
  track_config[TileSource::Home] = GetRailTrackBitsUniversal(ti->tile, &override_pcp);
  wire_config[TileSource::Home] = MaskWireBits(ti->tile, track_config[TileSource::Home]);
  /* If a track bit is present that is not in the main direction, the track is level */
  is_flat[TileSource::Home] = ((track_config[TileSource::Home] & (TRACK_BIT_HORZ | TRACK_BIT_VERT)) != 0);
 
  AdjustTileh(ti->tile, &tileh[TileSource::Home]);
 
  SpriteID pylon_normal = GetPylonBase(ti->tile);
  SpriteID pylon_halftile = (halftile_corner != CORNER_INVALID) ? GetPylonBase(ti->tile, TCX_UPPER_HALFTILE) : pylon_normal;
 
  for (DiagDirection i = DiagDirection::Begin; i < DiagDirection::End; i++) {
    SpriteID pylon_base = (halftile_corner != CORNER_INVALID && HasBit(InclinedSlope(i), halftile_corner)) ? pylon_halftile : pylon_normal;
    TileIndex neighbour = ti->tile + TileOffsByDiagDir(i);
    int elevation = GetPCPElevation(ti->tile, i);
 
    /* Here's one of the main headaches. GetTileSlope does not correct for possibly
     * existing foundataions, so we do have to do that manually later on.*/
    tileh[TileSource::Neighbour] = GetTileSlope(neighbour);
    track_config[TileSource::Neighbour] = GetRailTrackBitsUniversal(neighbour, nullptr);
    wire_config[TileSource::Neighbour] = MaskWireBits(neighbour, track_config[TileSource::Neighbour]);
    if (IsTunnelTile(neighbour) && i != GetTunnelBridgeDirection(neighbour)) wire_config[TileSource::Neighbour] = track_config[TileSource::Neighbour] = TRACK_BIT_NONE;
 
    /* Ignore station tiles that allow neither wires nor pylons. */
    if (HasStationTileRail(neighbour) && !CanStationTileHavePylons(neighbour) && !CanStationTileHaveWires(neighbour)) wire_config[TileSource::Neighbour] = track_config[TileSource::Neighbour] = TRACK_BIT_NONE;
 
    /* If the neighboured tile does not smoothly connect to the current tile (because of a foundation),
     * we have to draw all pillars on the current tile. */
    if (elevation != GetPCPElevation(neighbour, ReverseDiagDir(i))) wire_config[TileSource::Neighbour] = track_config[TileSource::Neighbour] = TRACK_BIT_NONE;
 
    is_flat[TileSource::Neighbour] = ((track_config[TileSource::Neighbour] & (TRACK_BIT_HORZ | TRACK_BIT_VERT)) != 0);
 
    ppp_preferred[i] = DIRECTIONS_ALL; // We start with preferring everything (end-of-line in any direction)
    ppp_allowed[i] = _allowed_ppp_on_pcp[i];
 
    /* We cycle through all the existing tracks at a PCP and see what
     * PPPs we want to have, or may not have at all */
    for (uint k = 0; k < NUM_TRACKS_AT_PCP; k++) {
      /* Next to us, we have a bridge head, don't worry about that one, if it shows away from us */
      if (_track_source_tile[i][k] == TileSource::Neighbour &&
          IsBridgeTile(neighbour) &&
          GetTunnelBridgeDirection(neighbour) == ReverseDiagDir(i)) {
        continue;
      }
 
      /* We check whether the track in question (k) is present in the tile
       * (TrackSourceTile) */
      DiagDirection pcp_pos = i;
      if (HasBit(wire_config[_track_source_tile[i][k]], _tracks_at_pcp[i][k])) {
        /* track found, if track is in the neighbour tile, adjust the number
         * of the PCP for preferred/allowed determination*/
        pcp_pos = (_track_source_tile[i][k] == TileSource::Home) ? i : ReverseDiagDir(i);
        pcp_status.Set(i); // This PCP is in use
        ppp_preferred[i] &= _preferred_ppp_of_track_at_pcp[_tracks_at_pcp[i][k]][pcp_pos];
      }
 
      if (HasBit(track_config[_track_source_tile[i][k]], _tracks_at_pcp[i][k])) {
        ppp_allowed[i].Reset(_disallowed_ppp_of_track_at_pcp[_tracks_at_pcp[i][k]][pcp_pos]);
      }
    }
 
    /* Deactivate all PPPs if PCP is not used */
    if (!pcp_status.Test(i)) {
      ppp_preferred[i].Reset();
      ppp_allowed[i].Reset();
    }
 
    Foundation foundation = FOUNDATION_NONE;
 
    /* Station and road crossings are always "flat", so adjust the tileh accordingly */
    if (IsTileType(neighbour, TileType::Station) || IsTileType(neighbour, TileType::Road)) tileh[TileSource::Neighbour] = SLOPE_FLAT;
 
    /* Read the foundations if they are present, and adjust the tileh */
    if (track_config[TileSource::Neighbour] != TRACK_BIT_NONE && IsTileType(neighbour, TileType::Railway) && HasRailCatenary(GetRailType(neighbour))) foundation = GetRailFoundation(tileh[TileSource::Neighbour], track_config[TileSource::Neighbour]);
    if (IsBridgeTile(neighbour)) {
      foundation = GetBridgeFoundation(tileh[TileSource::Neighbour], DiagDirToAxis(GetTunnelBridgeDirection(neighbour)));
    }
 
    ApplyFoundationToSlope(foundation, tileh[TileSource::Neighbour]);
 
    /* Half tile slopes coincide only with horizontal/vertical track.
     * Faking a flat slope results in the correct sprites on positions. */
    if (IsHalftileSlope(tileh[TileSource::Neighbour])) tileh[TileSource::Neighbour] = SLOPE_FLAT;
 
    AdjustTileh(neighbour, &tileh[TileSource::Neighbour]);
 
    /* If we have a straight (and level) track, we want a pylon only every 2 tiles
     * Delete the PCP if this is the case.
     * Level means that the slope is the same, or the track is flat */
    if (tileh[TileSource::Home] == tileh[TileSource::Neighbour] || (is_flat[TileSource::Home] && is_flat[TileSource::Neighbour])) {
      for (uint k = 0; k < NUM_IGNORE_GROUPS; k++) {
        if (ppp_preferred[i] == _ignored_pcp[k][tlg][i]) pcp_status.Reset(i);
      }
    }
 
    /* Now decide where we draw our pylons. First try the preferred PPPs, but they may not exist.
     * In that case, we try the any of the allowed ones. if they don't exist either, don't draw
     * anything. Note that the preferred PPPs still contain the end-of-line markers.
     * Remove those (simply by ANDing with allowed, since these markers are never allowed) */
    if (ppp_allowed[i].Any(ppp_preferred[i])) ppp_allowed[i] &= ppp_preferred[i];
 
    if (IsBridgeAbove(ti->tile)) {
      Track bridgetrack = AxisToTrack(GetBridgeAxis(ti->tile));
      int height = GetBridgeHeight(GetNorthernBridgeEnd(ti->tile));
 
      if ((height <= GetTileMaxZ(ti->tile) + 1) &&
          (i == _pcp_positions[bridgetrack][0] || i == _pcp_positions[bridgetrack][1])) {
        override_pcp.Set(i);
      }
    }
 
    if (ppp_allowed[i].Any() && pcp_status.Test(i) && !override_pcp.Test(i) &&
        (!HasStationTileRail(ti->tile) || CanStationTileHavePylons(ti->tile))) {
 
      const auto &ppp_orders = _ppp_order[i][GetTileLocationGroup(ti->tile)];
      for (Direction k = Direction::Begin; k < Direction::End; k++) {
        Direction temp = ppp_orders[k];
 
        if (ppp_allowed[i].Test(temp)) {
          uint x = ti->x + _x_pcp_offsets[i] + _x_ppp_offsets[temp];
          uint y = ti->y + _y_pcp_offsets[i] + _y_ppp_offsets[temp];
 
          /* Don't build the pylon if it would be outside the tile */
          if (!_owned_ppp_on_pcp[i].Test(temp)) {
            /* We have a neighbour that will draw it, bail out */
            if (track_config[TileSource::Neighbour] != TRACK_BIT_NONE) break;
            continue; // No neighbour, go looking for a better position
          }
 
          AddSortableSpriteToDraw(pylon_base + _pylon_sprites[temp], PAL_NONE, x, y, elevation,
            {{-1, -1, 0}, {1, 1, BB_HEIGHT_UNDER_BRIDGE}, {1, 1, 0}}, IsTransparencySet(TransparencyOption::Catenary));
 
          break; // We already have drawn a pylon, bail out
        }
      }
    }
  }
 
  /* The wire above the tunnel is drawn together with the tunnel-roof (see DrawRailCatenaryOnTunnel()) */
  if (IsTunnelTile(ti->tile)) return;
 
  /* Don't draw a wire under a low bridge */
  if (IsBridgeAbove(ti->tile) && !IsTransparencySet(TransparencyOption::Bridges)) {
    int height = GetBridgeHeight(GetNorthernBridgeEnd(ti->tile));
 
    if (height <= GetTileMaxZ(ti->tile) + 1) return;
  }
 
  /* Don't draw a wire if the station tile does not want any */
  if (HasStationTileRail(ti->tile) && !CanStationTileHaveWires(ti->tile)) return;
 
  SpriteID wire_normal = GetWireBase(ti->tile);
  SpriteID wire_halftile = (halftile_corner != CORNER_INVALID) ? GetWireBase(ti->tile, TCX_UPPER_HALFTILE) : wire_normal;
  Track halftile_track;
  switch (halftile_corner) {
    case CORNER_W: halftile_track = TRACK_LEFT; break;
    case CORNER_S: halftile_track = TRACK_LOWER; break;
    case CORNER_E: halftile_track = TRACK_RIGHT; break;
    case CORNER_N: halftile_track = TRACK_UPPER; break;
    default:       halftile_track = INVALID_TRACK; break;
  }
 
  /* Drawing of pylons is finished, now draw the wires */
  for (Track t : SetTrackBitIterator(wire_config[TileSource::Home])) {
    SpriteID wire_base = (t == halftile_track) ? wire_halftile : wire_normal;
    uint8_t pcp_config = pcp_status.Test(_pcp_positions[t][0]) +
      (pcp_status.Test(_pcp_positions[t][1]) << 1);
    int tileh_selector = !(tileh[TileSource::Home] % 3) * tileh[TileSource::Home] / 3; // tileh for the slopes, 0 otherwise
 
    assert(pcp_config != 0); // We have a pylon on neither end of the wire, that doesn't work (since we have no sprites for that)
    assert(!IsSteepSlope(tileh[TileSource::Home]));
    const SortableSpriteStruct &sss = _rail_catenary_sprite_data[_rail_wires[tileh_selector][t][pcp_config]];
 
    /*
     * The "wire"-sprite position is inside the tile, i.e. 0 <= sss->?_offset < TILE_SIZE.
     * Therefore it is safe to use GetSlopePixelZ() for the elevation.
     * Also note that the result of GetSlopePixelZ() is very special for bridge-ramps, so we round the result up or
     * down to the nearest full height change.
     */
    int z = (GetSlopePixelZ(ti->x + sss.origin.x, ti->y + sss.origin.y, true) + 4) / 8 * 8;
    AddSortableSpriteToDraw(wire_base + sss.image_offset, PAL_NONE, ti->x, ti->y, z, sss, IsTransparencySet(TransparencyOption::Catenary));
  }
}

void DrawRailCatenaryOnBridge(const TileInfo *ti)
{
  TileIndex end = GetSouthernBridgeEnd(ti->tile);
  TileIndex start = GetOtherBridgeEnd(end);
 
  uint length = GetTunnelBridgeLength(start, end);
  uint num = GetTunnelBridgeLength(ti->tile, start) + 1;
 
  Axis axis = GetBridgeAxis(ti->tile);
  TileLocationGroup tlg = GetTileLocationGroup(ti->tile);
 
  RailCatenarySprite offset = (RailCatenarySprite)(axis == Axis::X ? 0 : WIRE_Y_FLAT_BOTH - WIRE_X_FLAT_BOTH);
 
  const SortableSpriteStruct *sss;
  if ((length % 2) && num == length) {
    /* Draw the "short" wire on the southern end of the bridge
     * only needed if the length of the bridge is odd */
    sss = &_rail_catenary_sprite_data[WIRE_X_FLAT_BOTH + offset];
  } else {
    /* Draw "long" wires on all other tiles of the bridge (one pylon every two tiles) */
    sss = &_rail_catenary_sprite_data[WIRE_X_FLAT_SW + (num % 2) + offset];
  }
 
  uint height = GetBridgePixelHeight(end);
 
  SpriteID wire_base = GetWireBase(end, TCX_ON_BRIDGE);
 
  AddSortableSpriteToDraw(wire_base + sss->image_offset, PAL_NONE, ti->x, ti->y, height, *sss, IsTransparencySet(TransparencyOption::Catenary));
 
  SpriteID pylon_base = GetPylonBase(end, TCX_ON_BRIDGE);
 
  static constexpr SpriteBounds pylon_bounds{{-1, -1, 0}, {1, 1, BB_HEIGHT_UNDER_BRIDGE}, {1, 1, 0}};
 
  /* Finished with wires, draw pylons
   * every other tile needs a pylon on the northern end */
  if (num % 2) {
    DiagDirection pcp_pos = (axis == Axis::X ? DiagDirection::NE : DiagDirection::NW);
    Direction ppp_pos = (axis == Axis::X ? Direction::NW : Direction::NE);
    if (HasBit(tlg, (axis == Axis::X ? 0 : 1))) ppp_pos = ReverseDir(ppp_pos);
    uint x = ti->x + _x_pcp_offsets[pcp_pos] + _x_ppp_offsets[ppp_pos];
    uint y = ti->y + _y_pcp_offsets[pcp_pos] + _y_ppp_offsets[ppp_pos];
    AddSortableSpriteToDraw(pylon_base + _pylon_sprites[ppp_pos], PAL_NONE, x, y, height, pylon_bounds, IsTransparencySet(TransparencyOption::Catenary));
  }
 
  /* need a pylon on the southern end of the bridge */
  if (GetTunnelBridgeLength(ti->tile, start) + 1 == length) {
    DiagDirection pcp_pos = (axis == Axis::X ? DiagDirection::SW : DiagDirection::SE);
    Direction ppp_pos = (axis == Axis::X ? Direction::NW : Direction::NE);
    if (HasBit(tlg, (axis == Axis::X ? 0 : 1))) ppp_pos = ReverseDir(ppp_pos);
    uint x = ti->x + _x_pcp_offsets[pcp_pos] + _x_ppp_offsets[ppp_pos];
    uint y = ti->y + _y_pcp_offsets[pcp_pos] + _y_ppp_offsets[ppp_pos];
    AddSortableSpriteToDraw(pylon_base + _pylon_sprites[ppp_pos], PAL_NONE, x, y, height, pylon_bounds, IsTransparencySet(TransparencyOption::Catenary));
  }
}

void DrawRailCatenary(const TileInfo *ti)
{
  switch (GetTileType(ti->tile)) {
    case TileType::Railway:
      if (IsRailDepot(ti->tile)) {
        const SortableSpriteStruct &sss = _rail_catenary_sprite_data_depot[GetRailDepotDirection(ti->tile)];
 
        SpriteID wire_base = GetWireBase(ti->tile);
 
        /* This wire is not visible with the default depot sprites */
        AddSortableSpriteToDraw(wire_base + sss.image_offset, PAL_NONE, ti->x, ti->y, GetTileMaxPixelZ(ti->tile), sss, IsTransparencySet(TransparencyOption::Catenary));
        return;
      }
      break;
 
    case TileType::TunnelBridge:
    case TileType::Road:
    case TileType::Station:
      break;
 
    default: return;
  }
  DrawRailCatenaryRailway(ti);
}

void SettingsDisableElrail(int32_t new_value)
{
  bool disable = (new_value != 0);
  UpdateDisableElrailSettingState(disable, true);
}
 
void UpdateDisableElrailSettingState(bool disable, bool update_vehicles)
{
  /* walk through all train engines */
  for (Engine *e : Engine::IterateType(VehicleType::Train)) {
    RailVehicleInfo *rv_info = &e->VehInfo<RailVehicleInfo>();
    /* update railtype of engines intended to use elrail */
    if (rv_info->intended_railtypes.Test(RAILTYPE_ELECTRIC)) {
      rv_info->railtypes.Set(RAILTYPE_ELECTRIC, !disable);
      rv_info->railtypes.Set(RAILTYPE_RAIL, disable || rv_info->intended_railtypes.Test(RAILTYPE_RAIL));
    }
  }
 
  /* when disabling elrails, make sure that all existing trains can run on
   *  normal rail too */
  if (disable) {
    for (Train *t : Train::Iterate()) {
      if (t->railtypes.Test(RAILTYPE_ELECTRIC)) {
        /* this railroad vehicle is now compatible only with elrail,
         *  so add there also normal rail compatibility */
        t->compatible_railtypes.Set(RAILTYPE_RAIL);
        t->railtypes.Reset(RAILTYPE_ELECTRIC);
        t->railtypes.Set(RAILTYPE_RAIL);
        t->flags.Set(VehicleRailFlag::AllowedOnNormalRail);
      }
    }
  }
 
  /* Fix the total power and acceleration for trains */
  if (update_vehicles) {
    for (Train *t : Train::Iterate()) {
      /* power and acceleration is cached only for front engines */
      if (t->IsFrontEngine()) {
        t->ConsistChanged(CCF_TRACK);
      }
    }
  }
 
  for (Company *c : Company::Iterate()) c->avail_railtypes = GetCompanyRailTypes(c->index);
 
  /* This resets the _last_built_railtype, which will be invalid for electric
   * rails. It may have unintended consequences if that function is ever
   * extended, though. */
  ReinitGuiAfterToggleElrail(disable);
}