newgrf_station.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 <http://www.gnu.org/licenses/>.
 */
 
#include "stdafx.h"
#include "debug.h"
#include "station_base.h"
#include "waypoint_base.h"
#include "roadstop_base.h"
#include "newgrf_cargo.h"
#include "newgrf_station.h"
#include "newgrf_spritegroup.h"
#include "newgrf_sound.h"
#include "newgrf_railtype.h"
#include "town.h"
#include "newgrf_town.h"
#include "company_func.h"
#include "tunnelbridge_map.h"
#include "newgrf_animation_base.h"
#include "newgrf_class_func.h"
#include "timer/timer_game_calendar.h"
 
#include "safeguards.h"
 
 
template <>
/* static */ void StationClass::InsertDefaults()
{
  /* Set up initial data */
  StationClass::Get(StationClass::Allocate(STATION_CLASS_LABEL_DEFAULT))->name = STR_STATION_CLASS_DFLT;
  StationClass::Get(StationClass::Allocate(STATION_CLASS_LABEL_DEFAULT))->Insert(nullptr);
  StationClass::Get(StationClass::Allocate(STATION_CLASS_LABEL_WAYPOINT))->name = STR_STATION_CLASS_WAYP;
  StationClass::Get(StationClass::Allocate(STATION_CLASS_LABEL_WAYPOINT))->Insert(nullptr);
}
 
template <>
bool StationClass::IsUIAvailable(uint) const
{
  return true;
}
 
/* Instantiate StationClass. */
template class NewGRFClass<StationSpec, StationClassID, STAT_CLASS_MAX>;
 
static const uint NUM_STATIONSSPECS_PER_STATION = 255; 
 
enum TriggerArea {
  TA_TILE,
  TA_PLATFORM,
  TA_WHOLE,
};
 
struct ETileArea : TileArea {
  ETileArea(const BaseStation *st, TileIndex tile, TriggerArea ta)
  {
    switch (ta) {
      default: NOT_REACHED();
 
      case TA_TILE:
        this->tile = tile;
        this->w    = 1;
        this->h    = 1;
        break;
 
      case TA_PLATFORM: {
        TileIndex start, end;
        Axis axis = GetRailStationAxis(tile);
        TileIndexDiff delta = TileOffsByDiagDir(AxisToDiagDir(axis));
 
        for (end = tile; IsRailStationTile(end + delta) && IsCompatibleTrainStationTile(end + delta, tile); end += delta) { /* Nothing */ }
        for (start = tile; IsRailStationTile(start - delta) && IsCompatibleTrainStationTile(start - delta, tile); start -= delta) { /* Nothing */ }
 
        this->tile = start;
        this->w = TileX(end) - TileX(start) + 1;
        this->h = TileY(end) - TileY(start) + 1;
        break;
      }
 
      case TA_WHOLE:
        st->GetTileArea(this, Station::IsExpected(st) ? STATION_RAIL : STATION_WAYPOINT);
        break;
    }
  }
};
 
 
uint32_t GetPlatformInfo(Axis axis, uint8_t tile, int platforms, int length, int x, int y, bool centred)
{
  uint32_t retval = 0;
 
  if (axis == AXIS_X) {
    Swap(platforms, length);
    Swap(x, y);
  }
 
  if (centred) {
    x -= platforms / 2;
    y -= length / 2;
    x = Clamp(x, -8, 7);
    y = Clamp(y, -8, 7);
    SB(retval,  0, 4, y & 0xF);
    SB(retval,  4, 4, x & 0xF);
  } else {
    SB(retval,  0, 4, std::min(15, y));
    SB(retval,  4, 4, std::min(15, length - y - 1));
    SB(retval,  8, 4, std::min(15, x));
    SB(retval, 12, 4, std::min(15, platforms - x - 1));
  }
  SB(retval, 16, 4, std::min(15, length));
  SB(retval, 20, 4, std::min(15, platforms));
  SB(retval, 24, 8, tile);
 
  return retval;
}
 
 
static TileIndex FindRailStationEnd(TileIndex tile, TileIndexDiff delta, bool check_type, bool check_axis)
{
  uint8_t orig_type = 0;
  Axis orig_axis = AXIS_X;
  StationID sid = GetStationIndex(tile);
 
  if (check_type) orig_type = GetCustomStationSpecIndex(tile);
  if (check_axis) orig_axis = GetRailStationAxis(tile);
 
  for (;;) {
    TileIndex new_tile = TileAdd(tile, delta);
 
    if (!IsTileType(new_tile, MP_STATION) || GetStationIndex(new_tile) != sid) break;
    if (!HasStationRail(new_tile)) break;
    if (check_type && GetCustomStationSpecIndex(new_tile) != orig_type) break;
    if (check_axis && GetRailStationAxis(new_tile) != orig_axis) break;
 
    tile = new_tile;
  }
  return tile;
}
 
 
static uint32_t GetPlatformInfoHelper(TileIndex tile, bool check_type, bool check_axis, bool centred)
{
  int tx = TileX(tile);
  int ty = TileY(tile);
  int sx = TileX(FindRailStationEnd(tile, TileDiffXY(-1,  0), check_type, check_axis));
  int sy = TileY(FindRailStationEnd(tile, TileDiffXY( 0, -1), check_type, check_axis));
  int ex = TileX(FindRailStationEnd(tile, TileDiffXY( 1,  0), check_type, check_axis)) + 1;
  int ey = TileY(FindRailStationEnd(tile, TileDiffXY( 0,  1), check_type, check_axis)) + 1;
 
  tx -= sx; ex -= sx;
  ty -= sy; ey -= sy;
 
  return GetPlatformInfo(GetRailStationAxis(tile), GetStationGfx(tile), ex, ey, tx, ty, centred);
}
 
 
static uint32_t GetRailContinuationInfo(TileIndex tile)
{
  /* Tile offsets and exit dirs for X axis */
  static const Direction x_dir[8] = { DIR_SW, DIR_NE, DIR_SE, DIR_NW, DIR_S, DIR_E, DIR_W, DIR_N };
  static const DiagDirection x_exits[8] = { DIAGDIR_SW, DIAGDIR_NE, DIAGDIR_SE, DIAGDIR_NW, DIAGDIR_SW, DIAGDIR_NE, DIAGDIR_SW, DIAGDIR_NE };
 
  /* Tile offsets and exit dirs for Y axis */
  static const Direction y_dir[8] = { DIR_SE, DIR_NW, DIR_SW, DIR_NE, DIR_S, DIR_W, DIR_E, DIR_N };
  static const DiagDirection y_exits[8] = { DIAGDIR_SE, DIAGDIR_NW, DIAGDIR_SW, DIAGDIR_NE, DIAGDIR_SE, DIAGDIR_NW, DIAGDIR_SE, DIAGDIR_NW };
 
  Axis axis = GetRailStationAxis(tile);
 
  /* Choose appropriate lookup table to use */
  const Direction *dir = axis == AXIS_X ? x_dir : y_dir;
  const DiagDirection *diagdir = axis == AXIS_X ? x_exits : y_exits;
 
  uint32_t res = 0;
  uint i;
 
  for (i = 0; i < lengthof(x_dir); i++, dir++, diagdir++) {
    TileIndex neighbour_tile = tile + TileOffsByDir(*dir);
    TrackBits trackbits = TrackStatusToTrackBits(GetTileTrackStatus(neighbour_tile, TRANSPORT_RAIL, 0));
    if (trackbits != TRACK_BIT_NONE) {
      /* If there is any track on the tile, set the bit in the second byte */
      SetBit(res, i + 8);
 
      /* With tunnels and bridges the tile has tracks, but they are not necessarily connected
       * with the next tile because the ramp is not going in the right direction. */
      if (IsTileType(neighbour_tile, MP_TUNNELBRIDGE) && GetTunnelBridgeDirection(neighbour_tile) != *diagdir) {
        continue;
      }
 
      /* If any track reaches our exit direction, set the bit in the lower byte */
      if (trackbits & DiagdirReachesTracks(*diagdir)) SetBit(res, i);
    }
  }
 
  return res;
}
 
 
/* Station Resolver Functions */
/* virtual */ uint32_t StationScopeResolver::GetRandomBits() const
{
  return (this->st == nullptr ? 0 : this->st->random_bits) | (this->tile == INVALID_TILE ? 0 : GetStationTileRandomBits(this->tile) << 16);
}
 
 
/* virtual */ uint32_t StationScopeResolver::GetTriggers() const
{
  return this->st == nullptr ? 0 : this->st->waiting_triggers;
}
 
 
static struct {
  uint32_t v40;
  uint32_t v41;
  uint32_t v45;
  uint32_t v46;
  uint32_t v47;
  uint32_t v49;
  uint8_t valid; 
} _svc;
 
TownScopeResolver *StationResolverObject::GetTown()
{
  if (!this->town_scope.has_value()) {
    Town *t = nullptr;
    if (this->station_scope.st != nullptr) {
      t = this->station_scope.st->town;
    } else if (this->station_scope.tile != INVALID_TILE) {
      t = ClosestTownFromTile(this->station_scope.tile, UINT_MAX);
    }
    if (t == nullptr) return nullptr;
    this->town_scope.emplace(*this, t, this->station_scope.st == nullptr);
  }
  return &*this->town_scope;
}
 
/* virtual */ uint32_t StationScopeResolver::GetVariable(uint8_t variable, [[maybe_unused]] uint32_t parameter, bool &available) const
{
  if (this->st == nullptr) {
    /* Station does not exist, so we're in a purchase list or the land slope check callback. */
    switch (variable) {
      case 0x40:
      case 0x41:
      case 0x46:
      case 0x47:
      case 0x49: return 0x2110000;        // Platforms, tracks & position
      case 0x42: return 0;                // Rail type (XXX Get current type from GUI?)
      case 0x43: return GetCompanyInfo(_current_company); // Station owner
      case 0x44: return 2;                // PBS status
      case 0x67: // Land info of nearby tile
        if (this->axis != INVALID_AXIS && this->tile != INVALID_TILE) {
          TileIndex tile = this->tile;
          if (parameter != 0) tile = GetNearbyTile(parameter, tile, true, this->axis); // only perform if it is required
 
          Slope tileh = GetTileSlope(tile);
          bool swap = (this->axis == AXIS_Y && HasBit(tileh, CORNER_W) != HasBit(tileh, CORNER_E));
 
          return GetNearbyTileInformation(tile, this->ro.grffile->grf_version >= 8) ^ (swap ? SLOPE_EW : 0);
        }
        break;
 
      case 0xFA: return ClampTo<uint16_t>(TimerGameCalendar::date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR); // Build date, clamped to a 16 bit value
    }
 
    available = false;
    return UINT_MAX;
  }
 
  switch (variable) {
    /* Calculated station variables */
    case 0x40:
      if (!HasBit(_svc.valid, 0)) { _svc.v40 = GetPlatformInfoHelper(this->tile, false, false, false); SetBit(_svc.valid, 0); }
      return _svc.v40;
 
    case 0x41:
      if (!HasBit(_svc.valid, 1)) { _svc.v41 = GetPlatformInfoHelper(this->tile, true,  false, false); SetBit(_svc.valid, 1); }
      return _svc.v41;
 
    case 0x42: return GetTerrainType(this->tile) | (GetReverseRailTypeTranslation(GetRailType(this->tile), this->statspec->grf_prop.grffile) << 8);
    case 0x43: return GetCompanyInfo(this->st->owner); // Station owner
    case 0x44: return HasStationReservation(this->tile) ? 7 : 4; // PBS status
    case 0x45:
      if (!HasBit(_svc.valid, 2)) { _svc.v45 = GetRailContinuationInfo(this->tile); SetBit(_svc.valid, 2); }
      return _svc.v45;
 
    case 0x46:
      if (!HasBit(_svc.valid, 3)) { _svc.v46 = GetPlatformInfoHelper(this->tile, false, false, true); SetBit(_svc.valid, 3); }
      return _svc.v46;
 
    case 0x47:
      if (!HasBit(_svc.valid, 4)) { _svc.v47 = GetPlatformInfoHelper(this->tile, true,  false, true); SetBit(_svc.valid, 4); }
      return _svc.v47;
 
    case 0x49:
      if (!HasBit(_svc.valid, 5)) { _svc.v49 = GetPlatformInfoHelper(this->tile, false, true, false); SetBit(_svc.valid, 5); }
      return _svc.v49;
 
    case 0x4A: // Animation frame of tile
      return GetAnimationFrame(this->tile);
 
    /* Variables which use the parameter */
    /* Variables 0x60 to 0x65 and 0x69 are handled separately below */
    case 0x66: { // Animation frame of nearby tile
      TileIndex tile = this->tile;
      if (parameter != 0) tile = GetNearbyTile(parameter, tile);
      return this->st->TileBelongsToRailStation(tile) ? GetAnimationFrame(tile) : UINT_MAX;
    }
 
    case 0x67: { // Land info of nearby tile
      Axis axis = GetRailStationAxis(this->tile);
      TileIndex tile = this->tile;
      if (parameter != 0) tile = GetNearbyTile(parameter, tile); // only perform if it is required
 
      Slope tileh = GetTileSlope(tile);
      bool swap = (axis == AXIS_Y && HasBit(tileh, CORNER_W) != HasBit(tileh, CORNER_E));
 
      return GetNearbyTileInformation(tile, this->ro.grffile->grf_version >= 8) ^ (swap ? SLOPE_EW : 0);
    }
 
    case 0x68: { // Station info of nearby tiles
      TileIndex nearby_tile = GetNearbyTile(parameter, this->tile);
 
      if (!HasStationTileRail(nearby_tile)) return 0xFFFFFFFF;
 
      uint32_t grfid = this->st->speclist[GetCustomStationSpecIndex(this->tile)].grfid;
      bool perpendicular = GetRailStationAxis(this->tile) != GetRailStationAxis(nearby_tile);
      bool same_station = this->st->TileBelongsToRailStation(nearby_tile);
      uint32_t res = GB(GetStationGfx(nearby_tile), 1, 2) << 12 | !!perpendicular << 11 | !!same_station << 10;
 
      if (IsCustomStationSpecIndex(nearby_tile)) {
        const auto &sm = BaseStation::GetByTile(nearby_tile)->speclist[GetCustomStationSpecIndex(nearby_tile)];
        res |= 1 << (sm.grfid != grfid ? 9 : 8) | ClampTo<uint8_t>(sm.localidx);
      }
      return res;
    }
 
    case 0x6A: { // GRFID of nearby station tiles
      TileIndex nearby_tile = GetNearbyTile(parameter, this->tile);
 
      if (!HasStationTileRail(nearby_tile)) return 0xFFFFFFFF;
      if (!IsCustomStationSpecIndex(nearby_tile)) return 0;
 
      const auto &sm = BaseStation::GetByTile(nearby_tile)->speclist[GetCustomStationSpecIndex(nearby_tile)];
      return sm.grfid;
    }
 
    case 0x6B: { // 16 bit Station ID of nearby tiles
      TileIndex nearby_tile = GetNearbyTile(parameter, this->tile);
 
      if (!HasStationTileRail(nearby_tile)) return 0xFFFFFFFF;
      if (!IsCustomStationSpecIndex(nearby_tile)) return 0xFFFE;
 
      uint32_t grfid = this->st->speclist[GetCustomStationSpecIndex(this->tile)].grfid;
 
      const auto &sm = BaseStation::GetByTile(nearby_tile)->speclist[GetCustomStationSpecIndex(nearby_tile)];
      if (sm.grfid == grfid) {
        return sm.localidx;
      }
 
      return 0xFFFE;
    }
 
    /* General station variables */
    case 0x82: return 50;
    case 0x84: return this->st->string_id;
    case 0x86: return 0;
    case 0xF0: return this->st->facilities;
    case 0xFA: return ClampTo<uint16_t>(this->st->build_date - CalendarTime::DAYS_TILL_ORIGINAL_BASE_YEAR);
  }
 
  return this->st->GetNewGRFVariable(this->ro, variable, parameter, available);
}
 
uint32_t Station::GetNewGRFVariable(const ResolverObject &object, uint8_t variable, uint8_t parameter, bool &available) const
{
  switch (variable) {
    case 0x48: { // Accepted cargo types
      uint32_t value = GetAcceptanceMask(this);
      return value;
    }
 
    case 0x8A: return this->had_vehicle_of_type;
    case 0xF1: return (this->airport.tile != INVALID_TILE) ? this->airport.GetSpec()->ttd_airport_type : ATP_TTDP_LARGE;
    case 0xF2: return (this->truck_stops != nullptr) ? this->truck_stops->status : 0;
    case 0xF3: return (this->bus_stops != nullptr)   ? this->bus_stops->status   : 0;
    case 0xF6: return this->airport.flags;
    case 0xF7: return GB(this->airport.flags, 8, 8);
  }
 
  /* Handle cargo variables with parameter, 0x60 to 0x65 and 0x69 */
  if ((variable >= 0x60 && variable <= 0x65) || variable == 0x69) {
    CargoID c = GetCargoTranslation(parameter, object.grffile);
 
    if (!IsValidCargoID(c)) {
      switch (variable) {
        case 0x62: return 0xFFFFFFFF;
        case 0x64: return 0xFF00;
        default:   return 0;
      }
    }
    const GoodsEntry *ge = &this->goods[c];
 
    switch (variable) {
      case 0x60: return std::min(ge->cargo.TotalCount(), 4095u);
      case 0x61: return ge->HasVehicleEverTriedLoading() ? ge->time_since_pickup : 0;
      case 0x62: return ge->HasRating() ? ge->rating : 0xFFFFFFFF;
      case 0x63: return ge->cargo.PeriodsInTransit();
      case 0x64: return ge->HasVehicleEverTriedLoading() ? ge->last_speed | (ge->last_age << 8) : 0xFF00;
      case 0x65: return GB(ge->status, GoodsEntry::GES_ACCEPTANCE, 1) << 3;
      case 0x69: {
        static_assert((int)GoodsEntry::GES_EVER_ACCEPTED + 1 == (int)GoodsEntry::GES_LAST_MONTH);
        static_assert((int)GoodsEntry::GES_EVER_ACCEPTED + 2 == (int)GoodsEntry::GES_CURRENT_MONTH);
        static_assert((int)GoodsEntry::GES_EVER_ACCEPTED + 3 == (int)GoodsEntry::GES_ACCEPTED_BIGTICK);
        return GB(ge->status, GoodsEntry::GES_EVER_ACCEPTED, 4);
      }
    }
  }
 
  /* Handle cargo variables (deprecated) */
  if (variable >= 0x8C && variable <= 0xEC) {
    const GoodsEntry *g = &this->goods[GB(variable - 0x8C, 3, 4)];
    switch (GB(variable - 0x8C, 0, 3)) {
      case 0: return g->cargo.TotalCount();
      case 1: return GB(std::min(g->cargo.TotalCount(), 4095u), 0, 4) | (GB(g->status, GoodsEntry::GES_ACCEPTANCE, 1) << 7);
      case 2: return g->time_since_pickup;
      case 3: return g->rating;
      case 4: return g->cargo.GetFirstStation();
      case 5: return g->cargo.PeriodsInTransit();
      case 6: return g->last_speed;
      case 7: return g->last_age;
    }
  }
 
  Debug(grf, 1, "Unhandled station variable 0x{:X}", variable);
 
  available = false;
  return UINT_MAX;
}
 
uint32_t Waypoint::GetNewGRFVariable(const ResolverObject &, uint8_t variable, [[maybe_unused]] uint8_t parameter, bool &available) const
{
  switch (variable) {
    case 0x48: return 0; // Accepted cargo types
    case 0x8A: return HVOT_WAYPOINT;
    case 0xF1: return 0; // airport type
    case 0xF2: return 0; // truck stop status
    case 0xF3: return 0; // bus stop status
    case 0xF6: return 0; // airport flags
    case 0xF7: return 0; // airport flags cont.
  }
 
  /* Handle cargo variables with parameter, 0x60 to 0x65 */
  if (variable >= 0x60 && variable <= 0x65) {
    return 0;
  }
 
  /* Handle cargo variables (deprecated) */
  if (variable >= 0x8C && variable <= 0xEC) {
    switch (GB(variable - 0x8C, 0, 3)) {
      case 3: return INITIAL_STATION_RATING;
      case 4: return INVALID_STATION;
      default: return 0;
    }
  }
 
  Debug(grf, 1, "Unhandled station variable 0x{:X}", variable);
 
  available = false;
  return UINT_MAX;
}
 
/* virtual */ const SpriteGroup *StationResolverObject::ResolveReal(const RealSpriteGroup *group) const
{
  if (this->station_scope.st == nullptr || !Station::IsExpected(this->station_scope.st)) {
    return group->loading[0];
  }
 
  uint cargo = 0;
  const Station *st = Station::From(this->station_scope.st);
 
  switch (this->station_scope.cargo_type) {
    case INVALID_CARGO:
    case SpriteGroupCargo::SG_DEFAULT_NA:
    case SpriteGroupCargo::SG_PURCHASE:
      cargo = 0;
      break;
 
    case SpriteGroupCargo::SG_DEFAULT:
      for (const GoodsEntry &ge : st->goods) {
        cargo += ge.cargo.TotalCount();
      }
      break;
 
    default:
      cargo = st->goods[this->station_scope.cargo_type].cargo.TotalCount();
      break;
  }
 
  if (HasBit(this->station_scope.statspec->flags, SSF_DIV_BY_STATION_SIZE)) cargo /= (st->train_station.w + st->train_station.h);
  cargo = std::min(0xfffu, cargo);
 
  if (cargo > this->station_scope.statspec->cargo_threshold) {
    if (!group->loading.empty()) {
      uint set = ((cargo - this->station_scope.statspec->cargo_threshold) * (uint)group->loading.size()) / (4096 - this->station_scope.statspec->cargo_threshold);
      return group->loading[set];
    }
  } else {
    if (!group->loaded.empty()) {
      uint set = (cargo * (uint)group->loaded.size()) / (this->station_scope.statspec->cargo_threshold + 1);
      return group->loaded[set];
    }
  }
 
  return group->loading[0];
}
 
GrfSpecFeature StationResolverObject::GetFeature() const
{
  return GSF_STATIONS;
}
 
uint32_t StationResolverObject::GetDebugID() const
{
  return this->station_scope.statspec->grf_prop.local_id;
}
 
StationResolverObject::StationResolverObject(const StationSpec *statspec, BaseStation *base_station, TileIndex tile,
    CallbackID callback, uint32_t callback_param1, uint32_t callback_param2)
  : ResolverObject(statspec->grf_prop.grffile, callback, callback_param1, callback_param2),
  station_scope(*this, statspec, base_station, tile)
{
  /* Invalidate all cached vars */
  _svc.valid = 0;
 
  CargoID ctype = SpriteGroupCargo::SG_DEFAULT_NA;
 
  if (this->station_scope.st == nullptr) {
    /* No station, so we are in a purchase list */
    ctype = SpriteGroupCargo::SG_PURCHASE;
  } else if (Station::IsExpected(this->station_scope.st)) {
    const Station *st = Station::From(this->station_scope.st);
    /* Pick the first cargo that we have waiting */
    for (const CargoSpec *cs : CargoSpec::Iterate()) {
      if (this->station_scope.statspec->grf_prop.spritegroup[cs->Index()] != nullptr &&
          st->goods[cs->Index()].cargo.TotalCount() > 0) {
        ctype = cs->Index();
        break;
      }
    }
  }
 
  if (this->station_scope.statspec->grf_prop.spritegroup[ctype] == nullptr) {
    ctype = SpriteGroupCargo::SG_DEFAULT;
  }
 
  /* Remember the cargo type we've picked */
  this->station_scope.cargo_type = ctype;
  this->root_spritegroup = this->station_scope.statspec->grf_prop.spritegroup[this->station_scope.cargo_type];
}
 
SpriteID GetCustomStationRelocation(const StationSpec *statspec, BaseStation *st, TileIndex tile, uint32_t var10)
{
  StationResolverObject object(statspec, st, tile, CBID_NO_CALLBACK, var10);
  const SpriteGroup *group = object.Resolve();
  if (group == nullptr || group->type != SGT_RESULT) return 0;
  return group->GetResult() - 0x42D;
}
 
SpriteID GetCustomStationFoundationRelocation(const StationSpec *statspec, BaseStation *st, TileIndex tile, uint layout, uint edge_info)
{
  /* callback_param1 == 2 means  we are resolving the foundation sprites. */
  StationResolverObject object(statspec, st, tile, CBID_NO_CALLBACK, 2, layout | (edge_info << 16));
 
  const SpriteGroup *group = object.Resolve();
  if (group == nullptr || group->type != SGT_RESULT) return 0;
 
  /* Note: SpriteGroup::Resolve zeroes all registers, so register 0x100 is initialised to 0. (compatibility) */
  return group->GetResult() + GetRegister(0x100);
}
 
 
uint16_t GetStationCallback(CallbackID callback, uint32_t param1, uint32_t param2, const StationSpec *statspec, BaseStation *st, TileIndex tile)
{
  StationResolverObject object(statspec, st, tile, callback, param1, param2);
  return object.ResolveCallback();
}
 
CommandCost PerformStationTileSlopeCheck(TileIndex north_tile, TileIndex cur_tile, const StationSpec *statspec, Axis axis, uint8_t plat_len, uint8_t numtracks)
{
  TileIndex diff = cur_tile - north_tile;
  Slope slope = GetTileSlope(cur_tile);
 
  StationResolverObject object(statspec, nullptr, cur_tile, CBID_STATION_LAND_SLOPE_CHECK,
      (slope << 4) | (slope ^ (axis == AXIS_Y && HasBit(slope, CORNER_W) != HasBit(slope, CORNER_E) ? SLOPE_EW : 0)),
      (numtracks << 24) | (plat_len << 16) | (axis == AXIS_Y ? TileX(diff) << 8 | TileY(diff) : TileY(diff) << 8 | TileX(diff)));
  object.station_scope.axis = axis;
 
  uint16_t cb_res = object.ResolveCallback();
 
  /* Failed callback means success. */
  if (cb_res == CALLBACK_FAILED) return CommandCost();
 
  /* The meaning of bit 10 is inverted for a grf version < 8. */
  if (statspec->grf_prop.grffile->grf_version < 8) ToggleBit(cb_res, 10);
  return GetErrorMessageFromLocationCallbackResult(cb_res, statspec->grf_prop.grffile, STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
}
 
 
int AllocateSpecToStation(const StationSpec *statspec, BaseStation *st, bool exec)
{
  uint i;
 
  if (statspec == nullptr || st == nullptr) return 0;
 
  for (i = 1; i < st->speclist.size() && i < NUM_STATIONSSPECS_PER_STATION; i++) {
    if (st->speclist[i].spec == nullptr && st->speclist[i].grfid == 0) break;
  }
 
  if (i == NUM_STATIONSSPECS_PER_STATION) {
    /* As final effort when the spec list is already full...
     * try to find the same spec and return that one. This might
     * result in slightly "wrong" (as per specs) looking stations,
     * but it's fairly unlikely that one reaches the limit anyways.
     */
    for (i = 1; i < st->speclist.size() && i < NUM_STATIONSSPECS_PER_STATION; i++) {
      if (st->speclist[i].spec == statspec) return i;
    }
 
    return -1;
  }
 
  if (exec) {
    if (i >= st->speclist.size()) st->speclist.resize(i + 1);
    st->speclist[i].spec     = statspec;
    st->speclist[i].grfid    = statspec->grf_prop.grffile->grfid;
    st->speclist[i].localidx = statspec->grf_prop.local_id;
 
    StationUpdateCachedTriggers(st);
  }
 
  return i;
}
 
 
void DeallocateSpecFromStation(BaseStation *st, uint8_t specindex)
{
  /* specindex of 0 (default) is never freeable */
  if (specindex == 0) return;
 
  ETileArea area = ETileArea(st, INVALID_TILE, TA_WHOLE);
  /* Check all tiles over the station to check if the specindex is still in use */
  for (TileIndex tile : area) {
    if (st->TileBelongsToRailStation(tile) && GetCustomStationSpecIndex(tile) == specindex) {
      return;
    }
  }
 
  /* This specindex is no longer in use, so deallocate it */
  st->speclist[specindex].spec     = nullptr;
  st->speclist[specindex].grfid    = 0;
  st->speclist[specindex].localidx = 0;
 
  /* If this was the highest spec index, reallocate */
  if (specindex == st->speclist.size() - 1) {
    size_t num_specs;
    for (num_specs = st->speclist.size() - 1; num_specs > 0; num_specs--) {
      if (st->speclist[num_specs].grfid != 0) break;
    }
 
    if (num_specs > 0) {
      st->speclist.resize(num_specs + 1);
    } else {
      st->speclist.clear();
      st->cached_anim_triggers = 0;
      st->cached_cargo_triggers = 0;
      return;
    }
  }
 
  StationUpdateCachedTriggers(st);
}
 
bool DrawStationTile(int x, int y, RailType railtype, Axis axis, StationClassID sclass, uint station)
{
  const DrawTileSprites *sprites = nullptr;
  const RailTypeInfo *rti = GetRailTypeInfo(railtype);
  PaletteID palette = COMPANY_SPRITE_COLOUR(_local_company);
  uint tile = 2;
 
  const StationSpec *statspec = StationClass::Get(sclass)->GetSpec(station);
  if (statspec == nullptr) return false;
 
  if (HasBit(statspec->callback_mask, CBM_STATION_DRAW_TILE_LAYOUT)) {
    uint16_t callback = GetStationCallback(CBID_STATION_DRAW_TILE_LAYOUT, 0, 0, statspec, nullptr, INVALID_TILE);
    if (callback != CALLBACK_FAILED) tile = callback & ~1;
  }
 
  uint32_t total_offset = rti->GetRailtypeSpriteOffset();
  uint32_t relocation = 0;
  uint32_t ground_relocation = 0;
  const NewGRFSpriteLayout *layout = nullptr;
  DrawTileSprites tmp_rail_layout;
 
  if (statspec->renderdata.empty()) {
    sprites = GetStationTileLayout(STATION_RAIL, tile + axis);
  } else {
    layout = &statspec->renderdata[(tile < statspec->renderdata.size()) ? tile + axis : (uint)axis];
    if (!layout->NeedsPreprocessing()) {
      sprites = layout;
      layout = nullptr;
    }
  }
 
  if (layout != nullptr) {
    /* Sprite layout which needs preprocessing */
    bool separate_ground = HasBit(statspec->flags, SSF_SEPARATE_GROUND);
    uint32_t var10_values = layout->PrepareLayout(total_offset, rti->fallback_railtype, 0, 0, separate_ground);
    for (uint8_t var10 : SetBitIterator(var10_values)) {
      uint32_t var10_relocation = GetCustomStationRelocation(statspec, nullptr, INVALID_TILE, var10);
      layout->ProcessRegisters(var10, var10_relocation, separate_ground);
    }
 
    tmp_rail_layout.seq = layout->GetLayout(&tmp_rail_layout.ground);
    sprites = &tmp_rail_layout;
    total_offset = 0;
  } else {
    /* Simple sprite layout */
    ground_relocation = relocation = GetCustomStationRelocation(statspec, nullptr, INVALID_TILE, 0);
    if (HasBit(sprites->ground.sprite, SPRITE_MODIFIER_CUSTOM_SPRITE)) {
      ground_relocation = GetCustomStationRelocation(statspec, nullptr, INVALID_TILE, 1);
    }
    ground_relocation += rti->fallback_railtype;
  }
 
  SpriteID image = sprites->ground.sprite;
  PaletteID pal = sprites->ground.pal;
  RailTrackOffset overlay_offset;
  if (rti->UsesOverlay() && SplitGroundSpriteForOverlay(nullptr, &image, &overlay_offset)) {
    SpriteID ground = GetCustomRailSprite(rti, INVALID_TILE, RTSG_GROUND);
    DrawSprite(image, PAL_NONE, x, y);
    DrawSprite(ground + overlay_offset, PAL_NONE, x, y);
  } else {
    image += HasBit(image, SPRITE_MODIFIER_CUSTOM_SPRITE) ? ground_relocation : total_offset;
    if (HasBit(pal, SPRITE_MODIFIER_CUSTOM_SPRITE)) pal += ground_relocation;
    DrawSprite(image, GroundSpritePaletteTransform(image, pal, palette), x, y);
  }
 
  DrawRailTileSeqInGUI(x, y, sprites, total_offset, relocation, palette);
 
  return true;
}
 
 
const StationSpec *GetStationSpec(TileIndex t)
{
  if (!IsCustomStationSpecIndex(t)) return nullptr;
 
  const BaseStation *st = BaseStation::GetByTile(t);
  uint specindex = GetCustomStationSpecIndex(t);
  return specindex < st->speclist.size() ? st->speclist[specindex].spec : nullptr;
}
 
uint16_t GetAnimStationCallback(CallbackID callback, uint32_t param1, uint32_t param2, const StationSpec *statspec, BaseStation *st, TileIndex tile, int)
{
  return GetStationCallback(callback, param1, param2, statspec, st, tile);
}
 
struct StationAnimationBase : public AnimationBase<StationAnimationBase, StationSpec, BaseStation, int, GetAnimStationCallback, TileAnimationFrameAnimationHelper<BaseStation> > {
  static const CallbackID cb_animation_speed      = CBID_STATION_ANIMATION_SPEED;
  static const CallbackID cb_animation_next_frame = CBID_STATION_ANIM_NEXT_FRAME;
 
  static const StationCallbackMask cbm_animation_speed      = CBM_STATION_ANIMATION_SPEED;
  static const StationCallbackMask cbm_animation_next_frame = CBM_STATION_ANIMATION_NEXT_FRAME;
};
 
void AnimateStationTile(TileIndex tile)
{
  const StationSpec *ss = GetStationSpec(tile);
  if (ss == nullptr) return;
 
  StationAnimationBase::AnimateTile(ss, BaseStation::GetByTile(tile), tile, HasBit(ss->flags, SSF_CB141_RANDOM_BITS));
}
 
void TriggerStationAnimation(BaseStation *st, TileIndex trigger_tile, StationAnimationTrigger trigger, CargoID cargo_type)
{
  /* List of coverage areas for each animation trigger */
  static const TriggerArea tas[] = {
    TA_TILE, TA_WHOLE, TA_WHOLE, TA_PLATFORM, TA_PLATFORM, TA_PLATFORM, TA_WHOLE
  };
 
  /* Get Station if it wasn't supplied */
  if (st == nullptr) st = BaseStation::GetByTile(trigger_tile);
 
  /* Check the cached animation trigger bitmask to see if we need
   * to bother with any further processing. */
  if (!HasBit(st->cached_anim_triggers, trigger)) return;
 
  uint16_t random_bits = Random();
  ETileArea area = ETileArea(st, trigger_tile, tas[trigger]);
 
  /* Check all tiles over the station to check if the specindex is still in use */
  for (TileIndex tile : area) {
    if (st->TileBelongsToRailStation(tile)) {
      const StationSpec *ss = GetStationSpec(tile);
      if (ss != nullptr && HasBit(ss->animation.triggers, trigger)) {
        CargoID cargo;
        if (!IsValidCargoID(cargo_type)) {
          cargo = INVALID_CARGO;
        } else {
          cargo = ss->grf_prop.grffile->cargo_map[cargo_type];
        }
        StationAnimationBase::ChangeAnimationFrame(CBID_STATION_ANIM_START_STOP, ss, st, tile, (random_bits << 16) | GB(Random(), 0, 16), (uint8_t)trigger | (cargo << 8));
      }
    }
  }
}
 
void TriggerStationRandomisation(Station *st, TileIndex trigger_tile, StationRandomTrigger trigger, CargoID cargo_type)
{
  /* List of coverage areas for each animation trigger */
  static const TriggerArea tas[] = {
    TA_WHOLE, TA_WHOLE, TA_PLATFORM, TA_PLATFORM, TA_PLATFORM, TA_PLATFORM
  };
 
  /* Get Station if it wasn't supplied */
  if (st == nullptr) st = Station::GetByTile(trigger_tile);
 
  /* Check the cached cargo trigger bitmask to see if we need
   * to bother with any further processing. */
  if (st->cached_cargo_triggers == 0) return;
  if (IsValidCargoID(cargo_type) && !HasBit(st->cached_cargo_triggers, cargo_type)) return;
 
  uint32_t whole_reseed = 0;
  ETileArea area = ETileArea(st, trigger_tile, tas[trigger]);
 
  /* Bitmask of completely empty cargo types to be matched. */
  CargoTypes empty_mask = (trigger == SRT_CARGO_TAKEN) ? GetEmptyMask(st) : 0;
 
  /* Store triggers now for var 5F */
  SetBit(st->waiting_triggers, trigger);
  uint32_t used_triggers = 0;
 
  /* Check all tiles over the station to check if the specindex is still in use */
  for (TileIndex tile : area) {
    if (st->TileBelongsToRailStation(tile)) {
      const StationSpec *ss = GetStationSpec(tile);
      if (ss == nullptr) continue;
 
      /* Cargo taken "will only be triggered if all of those
       * cargo types have no more cargo waiting." */
      if (trigger == SRT_CARGO_TAKEN) {
        if ((ss->cargo_triggers & ~empty_mask) != 0) continue;
      }
 
      if (!IsValidCargoID(cargo_type) || HasBit(ss->cargo_triggers, cargo_type)) {
        StationResolverObject object(ss, st, tile, CBID_RANDOM_TRIGGER, 0);
        object.waiting_triggers = st->waiting_triggers;
 
        const SpriteGroup *group = object.Resolve();
        if (group == nullptr) continue;
 
        used_triggers |= object.used_triggers;
 
        uint32_t reseed = object.GetReseedSum();
        if (reseed != 0) {
          whole_reseed |= reseed;
          reseed >>= 16;
 
          /* Set individual tile random bits */
          uint8_t random_bits = GetStationTileRandomBits(tile);
          random_bits &= ~reseed;
          random_bits |= Random() & reseed;
          SetStationTileRandomBits(tile, random_bits);
 
          MarkTileDirtyByTile(tile);
        }
      }
    }
  }
 
  /* Update whole station random bits */
  st->waiting_triggers &= ~used_triggers;
  if ((whole_reseed & 0xFFFF) != 0) {
    st->random_bits &= ~whole_reseed;
    st->random_bits |= Random() & whole_reseed;
  }
}
 
void StationUpdateCachedTriggers(BaseStation *st)
{
  st->cached_anim_triggers = 0;
  st->cached_cargo_triggers = 0;
 
  /* Combine animation trigger bitmask for all station specs
   * of this station. */
  for (const auto &sm : GetStationSpecList<StationSpec>(st)) {
    if (sm.spec == nullptr) continue;
    st->cached_anim_triggers |= sm.spec->animation.triggers;
    st->cached_cargo_triggers |= sm.spec->cargo_triggers;
  }
}