town_cmd.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 "misc/history_type.hpp"
#include "misc/history_func.hpp"
#include "road.h"
#include "road_internal.h" /* Cleaning up road bits */
#include "road_cmd.h"
#include "landscape.h"
#include "viewport_func.h"
#include "viewport_kdtree.h"
#include "command_func.h"
#include "company_func.h"
#include "industry.h"
#include "station_base.h"
#include "waypoint_base.h"
#include "station_kdtree.h"
#include "company_base.h"
#include "news_func.h"
#include "error.h"
#include "object.h"
#include "genworld.h"
#include "newgrf_debug.h"
#include "newgrf_house.h"
#include "newgrf_text.h"
#include "autoslope.h"
#include "tunnelbridge_map.h"
#include "strings_func.h"
#include "window_func.h"
#include "string_func.h"
#include "newgrf_cargo.h"
#include "cheat_type.h"
#include "animated_tile_func.h"
#include "subsidy_func.h"
#include "core/pool_func.hpp"
#include "town.h"
#include "town_kdtree.h"
#include "townname_func.h"
#include "core/random_func.hpp"
#include "core/backup_type.hpp"
#include "depot_base.h"
#include "object_map.h"
#include "object_base.h"
#include "ai/ai.hpp"
#include "game/game.hpp"
#include "town_cmd.h"
#include "landscape_cmd.h"
#include "road_cmd.h"
#include "terraform_cmd.h"
#include "tunnelbridge_cmd.h"
#include "timer/timer.h"
#include "timer/timer_game_calendar.h"
#include "timer/timer_game_economy.h"
#include "timer/timer_game_tick.h"
 
#include "table/strings.h"
#include "table/town_land.h"
 
#include "safeguards.h"
 
/* Initialize the town-pool */
TownPool _town_pool("Town");
INSTANTIATE_POOL_METHODS(Town)
 
 
TownKdtree _town_kdtree{};
 
void RebuildTownKdtree()
{
  std::vector<TownID> townids;
  for (const Town *town : Town::Iterate()) {
    townids.push_back(town->index);
  }
  _town_kdtree.Build(townids.begin(), townids.end());
}
 
static bool _generating_town = false;
 
static bool TestTownOwnsBridge(TileIndex tile, const Town *t)
{
  if (!IsTileOwner(tile, OWNER_TOWN)) return false;
 
  TileIndex adjacent = tile + TileOffsByDiagDir(ReverseDiagDir(GetTunnelBridgeDirection(tile)));
  bool town_owned = IsTileType(adjacent, MP_ROAD) && IsTileOwner(adjacent, OWNER_TOWN) && GetTownIndex(adjacent) == t->index;
 
  if (!town_owned) {
    /* Or other adjacent road */
    adjacent = tile + TileOffsByDiagDir(ReverseDiagDir(GetTunnelBridgeDirection(GetOtherTunnelBridgeEnd(tile))));
    town_owned = IsTileType(adjacent, MP_ROAD) && IsTileOwner(adjacent, OWNER_TOWN) && GetTownIndex(adjacent) == t->index;
  }
 
  return town_owned;
}
static bool TestTownOwnsBridge(TileIndex tile, const Town *t) {…}
 
Town::~Town()
{
  if (CleaningPool()) return;
 
  /* Delete town authority window
   * and remove from list of sorted towns */
  CloseWindowById(WC_TOWN_VIEW, this->index);
  CloseWindowById(WC_TOWN_CARGO_GRAPH, this->index);
 
#ifdef WITH_ASSERT
  /* Check no industry is related to us. */
  for (const Industry *i : Industry::Iterate()) {
    assert(i->town != this);
  }
 
  /* ... and no object is related to us. */
  for (const Object *o : Object::Iterate()) {
    assert(o->town != this);
  }
 
  /* Check no tile is related to us. */
  for (const auto tile : Map::Iterate()) {
    switch (GetTileType(tile)) {
      case MP_HOUSE:
        assert(GetTownIndex(tile) != this->index);
        break;
 
      case MP_ROAD:
        assert(!HasTownOwnedRoad(tile) || GetTownIndex(tile) != this->index);
        break;
 
      case MP_TUNNELBRIDGE:
        assert(!TestTownOwnsBridge(tile, this));
        break;
 
      default:
        break;
    }
  }
#endif /* WITH_ASSERT */
 
  /* Clear the persistent storage list. */
  for (auto &psa : this->psa_list) {
    delete psa;
  }
  this->psa_list.clear();
 
  Source src{this->index, SourceType::Town};
  DeleteSubsidyWith(src);
  DeleteNewGRFInspectWindow(GSF_FAKE_TOWNS, this->index);
  CargoPacket::InvalidateAllFrom(src);
  MarkWholeScreenDirty();
}
Town::~Town() {…}
 
 
void Town::PostDestructor(size_t)
{
  InvalidateWindowData(WC_TOWN_DIRECTORY, 0, TDIWD_FORCE_REBUILD);
  UpdateNearestTownForRoadTiles(false);
 
  /* Give objects a new home! */
  for (Object *o : Object::Iterate()) {
    if (o->town == nullptr) o->town = CalcClosestTownFromTile(o->location.tile, UINT_MAX);
  }
}
void Town::PostDestructor(size_t) {…}
 
void Town::InitializeLayout(TownLayout layout)
{
  if (layout != TL_RANDOM) {
    this->layout = layout;
    return;
  }
 
  this->layout = static_cast<TownLayout>(TileHash(TileX(this->xy), TileY(this->xy)) % (NUM_TLS - 1));
}
void Town::InitializeLayout(TownLayout layout) {…}
 
/* static */ Town *Town::GetRandom()
{
  if (Town::GetNumItems() == 0) return nullptr;
  int num = RandomRange((uint16_t)Town::GetNumItems());
  size_t index = std::numeric_limits<size_t>::max();
 
  while (num >= 0) {
    num--;
    index++;
 
    /* Make sure we have a valid town */
    while (!Town::IsValidID(index)) {
      index++;
      assert(index < Town::GetPoolSize());
    }
  }
 
  return Town::Get(index);
}
/* static */ Town *Town::GetRandom() {…}
 
void Town::FillCachedName() const
{
  this->cached_name = GetTownName(this);
}
 
Money HouseSpec::GetRemovalCost() const
{
  return (_price[PR_CLEAR_HOUSE] * this->removal_cost) >> 8;
}
Money HouseSpec::GetRemovalCost() const {…}
 
static bool TryBuildTownHouse(Town *t, TileIndex tile, TownExpandModes modes);
static Town *CreateRandomTown(uint attempts, uint32_t townnameparts, TownSize size, bool city, TownLayout layout);
 
static void TownDrawHouseLift(const TileInfo *ti)
{
  AddChildSpriteScreen(SPR_LIFT, PAL_NONE, 14, 60 - GetLiftPosition(ti->tile));
}
 
typedef void TownDrawTileProc(const TileInfo *ti);
static TownDrawTileProc * const _town_draw_tile_procs[1] = {
  TownDrawHouseLift
};
 
static inline DiagDirection RandomDiagDir()
{
  return (DiagDirection)(RandomRange(DIAGDIR_END));
}
static inline DiagDirection RandomDiagDir() {…}
 
static void DrawTile_Town(TileInfo *ti)
{
  HouseID house_id = GetHouseType(ti->tile);
 
  if (house_id >= NEW_HOUSE_OFFSET) {
    /* Houses don't necessarily need new graphics. If they don't have a
     * spritegroup associated with them, then the sprite for the substitute
     * house id is drawn instead. */
    if (HouseSpec::Get(house_id)->grf_prop.HasSpriteGroups()) {
      DrawNewHouseTile(ti, house_id);
      return;
    } else {
      house_id = HouseSpec::Get(house_id)->grf_prop.subst_id;
    }
  }
 
  /* Retrieve pointer to the draw town tile struct */
  const DrawBuildingsTileStruct *dcts = &_town_draw_tile_data[house_id << 4 | TileHash2Bit(ti->x, ti->y) << 2 | GetHouseBuildingStage(ti->tile)];
 
  if (ti->tileh != SLOPE_FLAT) DrawFoundation(ti, FOUNDATION_LEVELED);
 
  DrawGroundSprite(dcts->ground.sprite, dcts->ground.pal);
 
  /* If houses are invisible, do not draw the upper part */
  if (IsInvisibilitySet(TO_HOUSES)) return;
 
  /* Add a house on top of the ground? */
  SpriteID image = dcts->building.sprite;
  if (image != 0) {
    AddSortableSpriteToDraw(image, dcts->building.pal, *ti, *dcts, IsTransparencySet(TO_HOUSES));
 
    if (IsTransparencySet(TO_HOUSES)) return;
  }
 
  {
    int proc = dcts->draw_proc - 1;
 
    if (proc >= 0) _town_draw_tile_procs[proc](ti);
  }
}
static void DrawTile_Town(TileInfo *ti) {…}
 
static int GetSlopePixelZ_Town(TileIndex tile, uint, uint, bool)
{
  return GetTileMaxPixelZ(tile);
}
 
static Foundation GetFoundation_Town(TileIndex tile, Slope tileh)
{
  HouseID hid = GetHouseType(tile);
 
  /* For NewGRF house tiles we might not be drawing a foundation. We need to
   * account for this, as other structures should
   * draw the wall of the foundation in this case.
   */
  if (hid >= NEW_HOUSE_OFFSET) {
    const HouseSpec *hs = HouseSpec::Get(hid);
    if (hs->callback_mask.Test(HouseCallbackMask::DrawFoundations)) {
      uint32_t callback_res = GetHouseCallback(CBID_HOUSE_DRAW_FOUNDATIONS, 0, 0, hid, Town::GetByTile(tile), tile);
      if (callback_res != CALLBACK_FAILED && !ConvertBooleanCallback(hs->grf_prop.grffile, CBID_HOUSE_DRAW_FOUNDATIONS, callback_res)) return FOUNDATION_NONE;
    }
  }
  return FlatteningFoundation(tileh);
}
static Foundation GetFoundation_Town(TileIndex tile, Slope tileh) {…}
 
static void AnimateTile_Town(TileIndex tile)
{
  if (GetHouseType(tile) >= NEW_HOUSE_OFFSET) {
    AnimateNewHouseTile(tile);
    return;
  }
 
  if (TimerGameTick::counter & 3) return;
 
  /* If the house is not one with a lift anymore, then stop this animating.
   * Not exactly sure when this happens, but probably when a house changes.
   * Before this was just a return...so it'd leak animated tiles..
   * That bug seems to have been here since day 1?? */
  if (!HouseSpec::Get(GetHouseType(tile))->building_flags.Test(BuildingFlag::IsAnimated)) {
    DeleteAnimatedTile(tile);
    return;
  }
 
  if (!LiftHasDestination(tile)) {
    uint i;
 
    /* Building has 6 floors, number 0 .. 6, where 1 is illegal.
     * This is due to the fact that the first floor is, in the graphics,
     *  the height of 2 'normal' floors.
     * Furthermore, there are 6 lift positions from floor N (incl) to floor N + 1 (excl) */
    do {
      i = RandomRange(7);
    } while (i == 1 || i * 6 == GetLiftPosition(tile));
 
    SetLiftDestination(tile, i);
  }
 
  int pos = GetLiftPosition(tile);
  int dest = GetLiftDestination(tile) * 6;
  pos += (pos < dest) ? 1 : -1;
  SetLiftPosition(tile, pos);
 
  if (pos == dest) {
    HaltLift(tile);
    DeleteAnimatedTile(tile);
  }
 
  MarkTileDirtyByTile(tile);
}
static void AnimateTile_Town(TileIndex tile) {…}
 
static bool IsCloseToTown(TileIndex tile, uint dist)
{
  if (_town_kdtree.Count() == 0) return false;
  Town *t = Town::Get(_town_kdtree.FindNearest(TileX(tile), TileY(tile)));
  return DistanceManhattan(tile, t->xy) < dist;
}
static bool IsCloseToTown(TileIndex tile, uint dist) {…}
 
void Town::UpdateVirtCoord()
{
  Point pt = RemapCoords2(TileX(this->xy) * TILE_SIZE, TileY(this->xy) * TILE_SIZE);
 
  if (this->cache.sign.kdtree_valid) _viewport_sign_kdtree.Remove(ViewportSignKdtreeItem::MakeTown(this->index));
 
  std::string town_string;
  if (this->larger_town) {
    town_string = GetString(_settings_client.gui.population_in_label ? STR_VIEWPORT_TOWN_CITY_POP : STR_VIEWPORT_TOWN_CITY, this->index, this->cache.population);
  } else {
    town_string = GetString(_settings_client.gui.population_in_label ? STR_VIEWPORT_TOWN_POP : STR_TOWN_NAME, this->index, this->cache.population);
  }
 
  this->cache.sign.UpdatePosition(pt.x, pt.y - 24 * ZOOM_BASE,
    town_string,
    GetString(STR_TOWN_NAME, this->index, this->cache.population)
);
 
  _viewport_sign_kdtree.Insert(ViewportSignKdtreeItem::MakeTown(this->index));
 
  SetWindowDirty(WC_TOWN_VIEW, this->index);
}
void Town::UpdateVirtCoord() {…}
 
void UpdateAllTownVirtCoords()
{
  for (Town *t : Town::Iterate()) {
    t->UpdateVirtCoord();
  }
}
void UpdateAllTownVirtCoords() {…}
 
void ClearAllTownCachedNames()
{
  for (Town *t : Town::Iterate()) {
    t->cached_name.clear();
  }
}
void ClearAllTownCachedNames() {…}
 
static void ChangePopulation(Town *t, int mod)
{
  t->cache.population += mod;
  if (_generating_town) [[unlikely]] return;
 
  InvalidateWindowData(WC_TOWN_VIEW, t->index); // Cargo requirements may appear/vanish for small populations
  if (_settings_client.gui.population_in_label) t->UpdateVirtCoord();
 
  InvalidateWindowData(WC_TOWN_DIRECTORY, 0, TDIWD_POPULATION_CHANGE);
}
static void ChangePopulation(Town *t, int mod) {…}
 
uint32_t GetWorldPopulation()
{
  uint32_t pop = 0;
  for (const Town *t : Town::Iterate()) pop += t->cache.population;
  return pop;
}
uint32_t GetWorldPopulation() {…}
 
static void RemoveNearbyStations(Town *t, TileIndex tile, BuildingFlags flags)
{
  for (StationList::iterator it = t->stations_near.begin(); it != t->stations_near.end(); /* incremented inside loop */) {
    const Station *st = *it;
 
    bool covers_area = st->TileIsInCatchment(tile);
    if (flags.Any(BUILDING_2_TILES_Y))   covers_area |= st->TileIsInCatchment(tile + TileDiffXY(0, 1));
    if (flags.Any(BUILDING_2_TILES_X))   covers_area |= st->TileIsInCatchment(tile + TileDiffXY(1, 0));
    if (flags.Any(BUILDING_HAS_4_TILES)) covers_area |= st->TileIsInCatchment(tile + TileDiffXY(1, 1));
 
    if (covers_area && !st->CatchmentCoversTown(t->index)) {
      it = t->stations_near.erase(it);
    } else {
      ++it;
    }
  }
}
static void RemoveNearbyStations(Town *t, TileIndex tile, BuildingFlags flags) {…}
 
static void AdvanceSingleHouseConstruction(TileIndex tile)
{
  assert(IsTileType(tile, MP_HOUSE));
 
  /* Progress in construction stages */
  IncHouseConstructionTick(tile);
  if (GetHouseConstructionTick(tile) != 0) return;
 
  TriggerHouseAnimation_ConstructionStageChanged(tile, false);
 
  if (IsHouseCompleted(tile)) {
    /* Now that construction is complete, we can add the population of the
     * building to the town. */
    ChangePopulation(Town::GetByTile(tile), HouseSpec::Get(GetHouseType(tile))->population);
    ResetHouseAge(tile);
  }
  MarkTileDirtyByTile(tile);
}
static void AdvanceSingleHouseConstruction(TileIndex tile) {…}
 
static void AdvanceHouseConstruction(TileIndex tile)
{
  BuildingFlags flags = HouseSpec::Get(GetHouseType(tile))->building_flags;
  if (flags.Any(BUILDING_HAS_1_TILE))  AdvanceSingleHouseConstruction(TileAddXY(tile, 0, 0));
  if (flags.Any(BUILDING_2_TILES_Y))   AdvanceSingleHouseConstruction(TileAddXY(tile, 0, 1));
  if (flags.Any(BUILDING_2_TILES_X))   AdvanceSingleHouseConstruction(TileAddXY(tile, 1, 0));
  if (flags.Any(BUILDING_HAS_4_TILES)) AdvanceSingleHouseConstruction(TileAddXY(tile, 1, 1));
}
static void AdvanceHouseConstruction(TileIndex tile) {…}
 
static void TownGenerateCargo(Town *t, CargoType cargo, uint amount, StationFinder &stations, bool affected_by_recession)
{
  if (amount == 0) return;
 
  /* All production is halved during a recession (except for NewGRF-supplied town cargo). */
  if (affected_by_recession && EconomyIsInRecession()) {
    amount = (amount + 1) >> 1;
  }
 
  /* Scale by cargo scale setting. */
  amount = ScaleByCargoScale(amount, true);
  if (amount == 0) return;
 
  /* Actually generate cargo and update town statistics. */
  auto &supplied = t->GetOrCreateCargoSupplied(cargo);
  supplied.history[THIS_MONTH].production += amount;
  supplied.history[THIS_MONTH].transported += MoveGoodsToStation(cargo, amount, {t->index, SourceType::Town}, stations.GetStations());;
}
static void TownGenerateCargo(Town *t, CargoType cargo, uint amount, StationFinder &stations, bool affected_by_recession) {…}
 
static void TownGenerateCargoOriginal(Town *t, TownProductionEffect tpe, uint8_t rate, StationFinder &stations)
{
  for (const CargoSpec *cs : CargoSpec::town_production_cargoes[tpe]) {
    uint32_t r = Random();
    if (GB(r, 0, 8) < rate) {
      CargoType cargo_type = cs->Index();
      uint amt = (GB(r, 0, 8) * cs->town_production_multiplier / TOWN_PRODUCTION_DIVISOR) / 8 + 1;
 
      TownGenerateCargo(t, cargo_type, amt, stations, true);
    }
  }
}
static void TownGenerateCargoOriginal(Town *t, TownProductionEffect tpe, uint8_t rate, StationFinder &stations) {…}
 
static void TownGenerateCargoBinomial(Town *t, TownProductionEffect tpe, uint8_t rate, StationFinder &stations)
{
  for (const CargoSpec *cs : CargoSpec::town_production_cargoes[tpe]) {
    CargoType cargo_type = cs->Index();
    uint32_t r = Random();
 
    /* Make a bitmask with up to 32 bits set, one for each potential pax. */
    int genmax = (rate + 7) / 8;
    uint32_t genmask = (genmax >= 32) ? 0xFFFFFFFF : ((1 << genmax) - 1);
 
    /* Mask random value by potential pax and count number of actual pax. */
    uint amt = CountBits(r & genmask) * cs->town_production_multiplier / TOWN_PRODUCTION_DIVISOR;
 
    TownGenerateCargo(t, cargo_type, amt, stations, true);
  }
}
static void TownGenerateCargoBinomial(Town *t, TownProductionEffect tpe, uint8_t rate, StationFinder &stations) {…}
 
static void TileLoop_Town(TileIndex tile)
{
  HouseID house_id = GetHouseType(tile);
 
  /* NewHouseTileLoop returns false if Callback 21 succeeded, i.e. the house
   * doesn't exist any more, so don't continue here. */
  if (house_id >= NEW_HOUSE_OFFSET && !NewHouseTileLoop(tile)) return;
 
  if (!IsHouseCompleted(tile)) {
    /* Construction is not completed, so we advance a construction stage. */
    AdvanceHouseConstruction(tile);
    return;
  }
 
  const HouseSpec *hs = HouseSpec::Get(house_id);
 
  /* If the lift has a destination, it is already an animated tile. */
  if (hs->building_flags.Test(BuildingFlag::IsAnimated) &&
      house_id < NEW_HOUSE_OFFSET &&
      !LiftHasDestination(tile) &&
      Chance16(1, 2)) {
    AddAnimatedTile(tile);
  }
 
  Town *t = Town::GetByTile(tile);
  uint32_t r = Random();
 
  StationFinder stations(TileArea(tile, 1, 1));
 
  if (hs->callback_mask.Test(HouseCallbackMask::ProduceCargo)) {
    for (uint i = 0; i < 256; i++) {
      uint16_t callback = GetHouseCallback(CBID_HOUSE_PRODUCE_CARGO, i, r, house_id, t, tile);
 
      if (callback == CALLBACK_FAILED || callback == CALLBACK_HOUSEPRODCARGO_END) break;
 
      CargoType cargo = GetCargoTranslation(GB(callback, 8, 7), hs->grf_prop.grffile);
      if (!IsValidCargoType(cargo)) continue;
 
      uint amt = GB(callback, 0, 8);
      if (amt == 0) continue;
 
      /* NewGRF-supplied town cargos are not affected by recessions. */
      TownGenerateCargo(t, cargo, amt, stations, false);
    }
  } else {
    switch (_settings_game.economy.town_cargogen_mode) {
      case TCGM_ORIGINAL:
        /* Original (quadratic) cargo generation algorithm */
        TownGenerateCargoOriginal(t, TPE_PASSENGERS, hs->population, stations);
        TownGenerateCargoOriginal(t, TPE_MAIL, hs->mail_generation, stations);
        break;
 
      case TCGM_BITCOUNT:
        /* Binomial distribution per tick, by a series of coin flips */
        /* Reduce generation rate to a 1/4, using tile bits to spread out distribution.
         * As tick counter is incremented by 256 between each call, we ignore the lower 8 bits. */
        if (GB(TimerGameTick::counter, 8, 2) == GB(tile.base(), 0, 2)) {
          TownGenerateCargoBinomial(t, TPE_PASSENGERS, hs->population, stations);
          TownGenerateCargoBinomial(t, TPE_MAIL, hs->mail_generation, stations);
        }
        break;
 
      default:
        NOT_REACHED();
    }
  }
 
  Backup<CompanyID> cur_company(_current_company, OWNER_TOWN);
 
  if (hs->building_flags.Any(BUILDING_HAS_1_TILE) &&
      HasBit(t->flags, TOWN_IS_GROWING) &&
      CanDeleteHouse(tile) &&
      GetHouseAge(tile) >= hs->minimum_life &&
      --t->time_until_rebuild == 0) {
    t->time_until_rebuild = GB(r, 16, 8) + 192;
 
    ClearTownHouse(t, tile);
 
    /* Rebuild with another house? */
    if (GB(r, 24, 8) >= 12) {
      /* If we are multi-tile houses, make sure to replace the house
       * closest to city center. If we do not do this, houses tend to
       * wander away from roads and other houses. */
      if (hs->building_flags.Any(BUILDING_HAS_2_TILES)) {
        /* House tiles are always the most north tile. Move the new
         * house to the south if we are north of the city center. */
        TileIndexDiffC grid_pos = TileIndexToTileIndexDiffC(t->xy, tile);
        int x = Clamp(grid_pos.x, 0, 1);
        int y = Clamp(grid_pos.y, 0, 1);
 
        if (hs->building_flags.Test(BuildingFlag::Size2x2)) {
          tile = TileAddXY(tile, x, y);
        } else if (hs->building_flags.Test(BuildingFlag::Size1x2)) {
          tile = TileAddXY(tile, 0, y);
        } else if (hs->building_flags.Test(BuildingFlag::Size2x1)) {
          tile = TileAddXY(tile, x, 0);
        }
      }
 
      TownExpandModes modes{TownExpandMode::Buildings};
      if (_settings_game.economy.allow_town_roads) modes.Set(TownExpandMode::Roads);
 
      TryBuildTownHouse(t, tile, modes);
    }
  }
 
  cur_company.Restore();
}
static void TileLoop_Town(TileIndex tile) {…}
 
static CommandCost ClearTile_Town(TileIndex tile, DoCommandFlags flags)
{
  if (flags.Test(DoCommandFlag::Auto)) return CommandCost(STR_ERROR_BUILDING_MUST_BE_DEMOLISHED);
  if (!CanDeleteHouse(tile)) return CommandCost(STR_ERROR_BUILDING_IS_PROTECTED);
 
  const HouseSpec *hs = HouseSpec::Get(GetHouseType(tile));
 
  CommandCost cost(EXPENSES_CONSTRUCTION);
  cost.AddCost(hs->GetRemovalCost());
 
  int rating = hs->remove_rating_decrease;
  Town *t = Town::GetByTile(tile);
 
  if (Company::IsValidID(_current_company)) {
    if (!_cheats.magic_bulldozer.value && !flags.Test(DoCommandFlag::NoTestTownRating)) {
      /* NewGRFs can add indestructible houses. */
      if (rating > RATING_MAXIMUM) {
        return CommandCost(STR_ERROR_BUILDING_IS_PROTECTED);
      }
      /* If town authority controls removal, check the company's rating. */
      if (rating > t->ratings[_current_company] && _settings_game.difficulty.town_council_tolerance != TOWN_COUNCIL_PERMISSIVE) {
        return CommandCostWithParam(STR_ERROR_LOCAL_AUTHORITY_REFUSES_TO_ALLOW_THIS, t->index);
      }
    }
  }
 
  ChangeTownRating(t, -rating, RATING_HOUSE_MINIMUM, flags);
  if (flags.Test(DoCommandFlag::Execute)) {
    ClearTownHouse(t, tile);
  }
 
  return cost;
}
static CommandCost ClearTile_Town(TileIndex tile, DoCommandFlags flags) {…}
 
static void AddProducedCargo_Town(TileIndex tile, CargoArray &produced)
{
  HouseID house_id = GetHouseType(tile);
  const HouseSpec *hs = HouseSpec::Get(house_id);
  Town *t = Town::GetByTile(tile);
 
  if (hs->callback_mask.Test(HouseCallbackMask::ProduceCargo)) {
    for (uint i = 0; i < 256; i++) {
      uint16_t callback = GetHouseCallback(CBID_HOUSE_PRODUCE_CARGO, i, 0, house_id, t, tile);
 
      if (callback == CALLBACK_FAILED || callback == CALLBACK_HOUSEPRODCARGO_END) break;
 
      CargoType cargo = GetCargoTranslation(GB(callback, 8, 7), hs->grf_prop.grffile);
 
      if (!IsValidCargoType(cargo)) continue;
      produced[cargo]++;
    }
  } else {
    if (hs->population > 0) {
      for (const CargoSpec *cs : CargoSpec::town_production_cargoes[TPE_PASSENGERS]) {
        produced[cs->Index()]++;
      }
    }
    if (hs->mail_generation > 0) {
      for (const CargoSpec *cs : CargoSpec::town_production_cargoes[TPE_MAIL]) {
        produced[cs->Index()]++;
      }
    }
  }
}
 
static void AddAcceptedCargoSetMask(CargoType cargo, uint amount, CargoArray &acceptance, CargoTypes &always_accepted)
{
  if (!IsValidCargoType(cargo) || amount == 0) return;
  acceptance[cargo] += amount;
  SetBit(always_accepted, cargo);
}
static void AddAcceptedCargoSetMask(CargoType cargo, uint amount, CargoArray &acceptance, CargoTypes &always_accepted) {…}
 
void AddAcceptedCargoOfHouse(TileIndex tile, HouseID house, const HouseSpec *hs, Town *t, CargoArray &acceptance, CargoTypes &always_accepted)
{
  CargoType accepts[lengthof(hs->accepts_cargo)];
 
  /* Set the initial accepted cargo types */
  for (uint8_t i = 0; i < lengthof(accepts); i++) {
    accepts[i] = hs->accepts_cargo[i];
  }
 
  /* Check for custom accepted cargo types */
  if (hs->callback_mask.Test(HouseCallbackMask::AcceptCargo)) {
    uint16_t callback = GetHouseCallback(CBID_HOUSE_ACCEPT_CARGO, 0, 0, house, t, tile, {}, tile == INVALID_TILE);
    if (callback != CALLBACK_FAILED) {
      /* Replace accepted cargo types with translated values from callback */
      accepts[0] = GetCargoTranslation(GB(callback,  0, 5), hs->grf_prop.grffile);
      accepts[1] = GetCargoTranslation(GB(callback,  5, 5), hs->grf_prop.grffile);
      accepts[2] = GetCargoTranslation(GB(callback, 10, 5), hs->grf_prop.grffile);
    }
  }
 
  /* Check for custom cargo acceptance */
  if (hs->callback_mask.Test(HouseCallbackMask::CargoAcceptance)) {
    uint16_t callback = GetHouseCallback(CBID_HOUSE_CARGO_ACCEPTANCE, 0, 0, house, t, tile, {}, tile == INVALID_TILE);
    if (callback != CALLBACK_FAILED) {
      AddAcceptedCargoSetMask(accepts[0], GB(callback, 0, 4), acceptance, always_accepted);
      AddAcceptedCargoSetMask(accepts[1], GB(callback, 4, 4), acceptance, always_accepted);
      if (_settings_game.game_creation.landscape != LandscapeType::Temperate && HasBit(callback, 12)) {
        /* The 'S' bit indicates food instead of goods */
        AddAcceptedCargoSetMask(GetCargoTypeByLabel(CT_FOOD), GB(callback, 8, 4), acceptance, always_accepted);
      } else {
        AddAcceptedCargoSetMask(accepts[2], GB(callback, 8, 4), acceptance, always_accepted);
      }
      return;
    }
  }
 
  /* No custom acceptance, so fill in with the default values */
  for (uint8_t i = 0; i < lengthof(accepts); i++) {
    AddAcceptedCargoSetMask(accepts[i], hs->cargo_acceptance[i], acceptance, always_accepted);
  }
}
void AddAcceptedCargoOfHouse(TileIndex tile, HouseID house, const HouseSpec *hs, Town *t, CargoArray &acceptance, CargoTypes &always_accepted) {…}
 
static void AddAcceptedCargo_Town(TileIndex tile, CargoArray &acceptance, CargoTypes &always_accepted)
{
  HouseID house = GetHouseType(tile);
  AddAcceptedCargoOfHouse(tile, house, HouseSpec::Get(house), Town::GetByTile(tile), acceptance, always_accepted);
}
 
CargoArray GetAcceptedCargoOfHouse(const HouseSpec *hs)
{
  CargoTypes always_accepted{};
  CargoArray acceptance{};
  AddAcceptedCargoOfHouse(INVALID_TILE, hs->Index(), hs, nullptr, acceptance, always_accepted);
  return acceptance;
}
CargoArray GetAcceptedCargoOfHouse(const HouseSpec *hs) {…}
 
static void GetTileDesc_Town(TileIndex tile, TileDesc &td)
{
  const HouseID house = GetHouseType(tile);
  const HouseSpec *hs = HouseSpec::Get(house);
  bool house_completed = IsHouseCompleted(tile);
 
  td.str = hs->building_name;
  td.town_can_upgrade = !IsHouseProtected(tile);
 
  std::array<int32_t, 1> regs100;
  uint16_t callback_res = GetHouseCallback(CBID_HOUSE_CUSTOM_NAME, house_completed ? 1 : 0, 0, house, Town::GetByTile(tile), tile, regs100);
  if (callback_res != CALLBACK_FAILED && callback_res != 0x400) {
    StringID new_name = STR_NULL;
    if (callback_res == 0x40F) {
      new_name = GetGRFStringID(hs->grf_prop.grfid, static_cast<GRFStringID>(regs100[0]));
    } else if (callback_res > 0x400) {
      ErrorUnknownCallbackResult(hs->grf_prop.grfid, CBID_HOUSE_CUSTOM_NAME, callback_res);
    } else {
      new_name = GetGRFStringID(hs->grf_prop.grfid, GRFSTR_MISC_GRF_TEXT + callback_res);
    }
    if (new_name != STR_NULL && new_name != STR_UNDEFINED) {
      td.str = new_name;
    }
  }
 
  if (!house_completed) {
    td.dparam = td.str;
    td.str = STR_LAI_TOWN_INDUSTRY_DESCRIPTION_UNDER_CONSTRUCTION;
  }
 
  if (hs->grf_prop.HasGrfFile()) {
    const GRFConfig *gc = GetGRFConfig(hs->grf_prop.grfid);
    td.grf = gc->GetName();
  }
 
  td.owner[0] = OWNER_TOWN;
}
 
static TrackStatus GetTileTrackStatus_Town(TileIndex, TransportType, uint, DiagDirection)
{
  /* not used */
  return 0;
}
 
static void ChangeTileOwner_Town(TileIndex, Owner, Owner)
{
  /* not used */
}
 
static bool GrowTown(Town *t, TownExpandModes modes);
 
static void TownTickHandler(Town *t)
{
  if (HasBit(t->flags, TOWN_IS_GROWING)) {
    TownExpandModes modes{TownExpandMode::Buildings};
    if (_settings_game.economy.allow_town_roads) modes.Set(TownExpandMode::Roads);
    int i = (int)t->grow_counter - 1;
    if (i < 0) {
      if (GrowTown(t, modes)) {
        i = t->growth_rate;
      } else {
        /* If growth failed wait a bit before retrying */
        i = std::min<uint16_t>(t->growth_rate, Ticks::TOWN_GROWTH_TICKS - 1);
      }
    }
    t->grow_counter = i;
  }
}
static void TownTickHandler(Town *t) {…}
 
void OnTick_Town()
{
  if (_game_mode == GM_EDITOR) return;
 
  for (Town *t : Town::Iterate()) {
    TownTickHandler(t);
  }
}
void OnTick_Town() {…}
 
static RoadBits GetTownRoadBits(TileIndex tile)
{
  if (IsRoadDepotTile(tile) || IsBayRoadStopTile(tile)) return ROAD_NONE;
 
  return GetAnyRoadBits(tile, RTT_ROAD, true);
}
static RoadBits GetTownRoadBits(TileIndex tile) {…}
 
RoadType GetTownRoadType()
{
  RoadType best_rt = ROADTYPE_ROAD;
  const RoadTypeInfo *best = nullptr;
  const uint16_t assume_max_speed = 50;
 
  for (RoadType rt = ROADTYPE_BEGIN; rt != ROADTYPE_END; rt++) {
    if (RoadTypeIsTram(rt)) continue;
 
    const RoadTypeInfo *rti = GetRoadTypeInfo(rt);
 
    /* Unused road type. */
    if (rti->label == 0) continue;
 
    /* Can town build this road. */
    if (!rti->flags.Test(RoadTypeFlag::TownBuild)) continue;
 
    /* Not yet introduced at this date. */
    if (IsInsideMM(rti->introduction_date, 0, CalendarTime::MAX_DATE.base()) && rti->introduction_date > TimerGameCalendar::date) continue;
 
    if (best != nullptr) {
      if ((rti->max_speed == 0 ? assume_max_speed : rti->max_speed) < (best->max_speed == 0 ? assume_max_speed : best->max_speed)) continue;
    }
 
    best_rt = rt;
    best = rti;
  }
 
  return best_rt;
}
RoadType GetTownRoadType() {…}
 
static TimerGameCalendar::Date GetTownRoadTypeFirstIntroductionDate()
{
  const RoadTypeInfo *best = nullptr;
  for (RoadType rt = ROADTYPE_BEGIN; rt != ROADTYPE_END; rt++) {
    if (RoadTypeIsTram(rt)) continue;
    const RoadTypeInfo *rti = GetRoadTypeInfo(rt);
    if (rti->label == 0) continue; // Unused road type.
    if (!rti->flags.Test(RoadTypeFlag::TownBuild)) continue; // Town can't build this road type.
 
    if (best != nullptr && rti->introduction_date >= best->introduction_date) continue;
    best = rti;
  }
 
  if (best == nullptr) return TimerGameCalendar::Date(INT32_MAX);
  return best->introduction_date;
}
static TimerGameCalendar::Date GetTownRoadTypeFirstIntroductionDate() {…}
 
bool CheckTownRoadTypes()
{
  auto min_date = GetTownRoadTypeFirstIntroductionDate();
  if (min_date <= TimerGameCalendar::date) return true;
 
  if (min_date < INT32_MAX) {
    ShowErrorMessage(
      GetEncodedString(STR_ERROR_NO_TOWN_ROADTYPES_AVAILABLE_YET),
      GetEncodedString(STR_ERROR_NO_TOWN_ROADTYPES_AVAILABLE_YET_EXPLANATION, min_date),
      WL_CRITICAL);
  } else {
    ShowErrorMessage(
      GetEncodedString(STR_ERROR_NO_TOWN_ROADTYPES_AVAILABLE_AT_ALL),
      GetEncodedString(STR_ERROR_NO_TOWN_ROADTYPES_AVAILABLE_AT_ALL_EXPLANATION), WL_CRITICAL);
  }
  return false;
}
bool CheckTownRoadTypes() {…}
 
static bool IsNeighbourRoadTile(TileIndex tile, const DiagDirection dir, uint dist_multi)
{
  if (!IsValidTile(tile)) return false;
 
  /* Lookup table for the used diff values */
  const TileIndexDiff tid_lt[3] = {
    TileOffsByDiagDir(ChangeDiagDir(dir, DIAGDIRDIFF_90RIGHT)),
    TileOffsByDiagDir(ChangeDiagDir(dir, DIAGDIRDIFF_90LEFT)),
    TileOffsByDiagDir(ReverseDiagDir(dir)),
  };
 
  dist_multi = (dist_multi + 1) * 4;
  for (uint pos = 4; pos < dist_multi; pos++) {
    /* Go (pos / 4) tiles to the left or the right */
    TileIndexDiff cur = tid_lt[(pos & 1) ? 0 : 1] * (pos / 4);
 
    /* Use the current tile as origin, or go one tile backwards */
    if (pos & 2) cur += tid_lt[2];
 
    /* Test for roadbit parallel to dir and facing towards the middle axis */
    if (IsValidTile(tile + cur) &&
        GetTownRoadBits(TileAdd(tile, cur)) & DiagDirToRoadBits((pos & 2) ? dir : ReverseDiagDir(dir))) return true;
  }
  return false;
}
static bool IsNeighbourRoadTile(TileIndex tile, const DiagDirection dir, uint dist_multi) {…}
 
static bool IsRoadAllowedHere(Town *t, TileIndex tile, DiagDirection dir)
{
  if (DistanceFromEdge(tile) == 0) return false;
 
  /* Prevent towns from building roads under bridges along the bridge. Looks silly. */
  if (IsBridgeAbove(tile) && GetBridgeAxis(tile) == DiagDirToAxis(dir)) return false;
 
  /* Check if there already is a road at this point? */
  if (GetTownRoadBits(tile) == ROAD_NONE) {
    /* No, try if we are able to build a road piece there.
     * If that fails clear the land, and if that fails exit.
     * This is to make sure that we can build a road here later. */
    RoadType rt = GetTownRoadType();
    if (Command<CMD_BUILD_ROAD>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater}, tile, (dir == DIAGDIR_NW || dir == DIAGDIR_SE) ? ROAD_Y : ROAD_X, rt, DRD_NONE, t->index).Failed() &&
        Command<CMD_LANDSCAPE_CLEAR>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater}, tile).Failed()) {
      return false;
    }
  }
 
  Slope cur_slope = _settings_game.construction.build_on_slopes ? std::get<0>(GetFoundationSlope(tile)) : GetTileSlope(tile);
  bool ret = !IsNeighbourRoadTile(tile, dir, t->layout == TL_ORIGINAL ? 1 : 2);
  if (cur_slope == SLOPE_FLAT) return ret;
 
  /* If the tile is not a slope in the right direction, then
   * maybe terraform some. */
  Slope desired_slope = (dir == DIAGDIR_NW || dir == DIAGDIR_SE) ? SLOPE_NW : SLOPE_NE;
  if (desired_slope != cur_slope && ComplementSlope(desired_slope) != cur_slope) {
    if (Chance16(1, 8)) {
      CommandCost res = CMD_ERROR;
      if (!_generating_world && Chance16(1, 10)) {
        /* Note: Do not replace "^ SLOPE_ELEVATED" with ComplementSlope(). The slope might be steep. */
        res = std::get<0>(Command<CMD_TERRAFORM_LAND>::Do({DoCommandFlag::Execute, DoCommandFlag::Auto, DoCommandFlag::NoWater},
            tile, Chance16(1, 16) ? cur_slope : cur_slope ^ SLOPE_ELEVATED, false));
      }
      if (res.Failed() && Chance16(1, 3)) {
        /* We can consider building on the slope, though. */
        return ret;
      }
    }
    return false;
  }
  return ret;
}
static bool IsRoadAllowedHere(Town *t, TileIndex tile, DiagDirection dir) {…}
 
static bool TerraformTownTile(TileIndex tile, Slope edges, bool dir)
{
  assert(tile < Map::Size());
 
  CommandCost r = std::get<0>(Command<CMD_TERRAFORM_LAND>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater}, tile, edges, dir));
  if (r.Failed() || r.GetCost() >= (_price[PR_TERRAFORM] + 2) * 8) return false;
  Command<CMD_TERRAFORM_LAND>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater, DoCommandFlag::Execute}, tile, edges, dir);
  return true;
}
 
static void LevelTownLand(TileIndex tile)
{
  assert(tile < Map::Size());
 
  /* Don't terraform if land is plain or if there's a house there. */
  if (IsTileType(tile, MP_HOUSE)) return;
  Slope tileh = GetTileSlope(tile);
  if (tileh == SLOPE_FLAT) return;
 
  /* First try up, then down */
  if (!TerraformTownTile(tile, ~tileh & SLOPE_ELEVATED, true)) {
    TerraformTownTile(tile, tileh & SLOPE_ELEVATED, false);
  }
}
 
static RoadBits GetTownRoadGridElement(Town *t, TileIndex tile, DiagDirection dir)
{
  /* align the grid to the downtown */
  TileIndexDiffC grid_pos = TileIndexToTileIndexDiffC(t->xy, tile); // Vector from downtown to the tile
  RoadBits rcmd = ROAD_NONE;
 
  switch (t->layout) {
    default: NOT_REACHED();
 
    case TL_2X2_GRID:
      if ((grid_pos.x % 3) == 0) rcmd |= ROAD_Y;
      if ((grid_pos.y % 3) == 0) rcmd |= ROAD_X;
      break;
 
    case TL_3X3_GRID:
      if ((grid_pos.x % 4) == 0) rcmd |= ROAD_Y;
      if ((grid_pos.y % 4) == 0) rcmd |= ROAD_X;
      break;
  }
 
  /* Optimise only X-junctions */
  if (rcmd != ROAD_ALL) return rcmd;
 
  RoadBits rb_template;
 
  switch (GetTileSlope(tile)) {
    default:       rb_template = ROAD_ALL; break;
    case SLOPE_W:  rb_template = ROAD_NW | ROAD_SW; break;
    case SLOPE_SW: rb_template = ROAD_Y  | ROAD_SW; break;
    case SLOPE_S:  rb_template = ROAD_SW | ROAD_SE; break;
    case SLOPE_SE: rb_template = ROAD_X  | ROAD_SE; break;
    case SLOPE_E:  rb_template = ROAD_SE | ROAD_NE; break;
    case SLOPE_NE: rb_template = ROAD_Y  | ROAD_NE; break;
    case SLOPE_N:  rb_template = ROAD_NE | ROAD_NW; break;
    case SLOPE_NW: rb_template = ROAD_X  | ROAD_NW; break;
    case SLOPE_STEEP_W:
    case SLOPE_STEEP_S:
    case SLOPE_STEEP_E:
    case SLOPE_STEEP_N:
      rb_template = ROAD_NONE;
      break;
  }
 
  /* Stop if the template is compatible to the growth dir */
  if (DiagDirToRoadBits(ReverseDiagDir(dir)) & rb_template) return rb_template;
  /* If not generate a straight road in the direction of the growth */
  return DiagDirToRoadBits(dir) | DiagDirToRoadBits(ReverseDiagDir(dir));
}
static RoadBits GetTownRoadGridElement(Town *t, TileIndex tile, DiagDirection dir) {…}
 
static bool GrowTownWithExtraHouse(Town *t, TileIndex tile, TownExpandModes modes)
{
  /* We can't look further than that. */
  if (DistanceFromEdge(tile) == 0) return false;
 
  uint counter = 0; // counts the house neighbour tiles
 
  /* Check the tiles E,N,W and S of the current tile for houses */
  for (DiagDirection dir = DIAGDIR_BEGIN; dir < DIAGDIR_END; dir++) {
    /* Count both void and house tiles for checking whether there
     * are enough houses in the area. This to make it likely that
     * houses get build up to the edge of the map. */
    switch (GetTileType(TileAddByDiagDir(tile, dir))) {
      case MP_HOUSE:
      case MP_VOID:
        counter++;
        break;
 
      default:
        break;
    }
 
    /* If there are enough neighbours stop here */
    if (counter >= 3) {
      return TryBuildTownHouse(t, tile, modes);
    }
  }
  return false;
}
static bool GrowTownWithExtraHouse(Town *t, TileIndex tile, TownExpandModes modes) {…}
 
static bool GrowTownWithRoad(const Town *t, TileIndex tile, RoadBits rcmd)
{
  RoadType rt = GetTownRoadType();
  return Command<CMD_BUILD_ROAD>::Do({DoCommandFlag::Execute, DoCommandFlag::Auto, DoCommandFlag::NoWater}, tile, rcmd, rt, DRD_NONE, t->index).Succeeded();
}
static bool GrowTownWithRoad(const Town *t, TileIndex tile, RoadBits rcmd) {…}
 
static bool CanRoadContinueIntoNextTile(const Town *t, const TileIndex tile, const DiagDirection road_dir)
{
  const TileIndexDiff delta = TileOffsByDiagDir(road_dir); // +1 tile in the direction of the road
  TileIndex next_tile = tile + delta; // The tile beyond which must be connectable to the target tile
  RoadBits rcmd = DiagDirToRoadBits(ReverseDiagDir(road_dir));
  RoadType rt = GetTownRoadType();
 
  /* Before we try anything, make sure the tile is on the map and not the void. */
  if (!IsValidTile(next_tile)) return false;
 
  /* If the next tile is a bridge or tunnel, allow if it's continuing in the same direction. */
  if (IsTileType(next_tile, MP_TUNNELBRIDGE)) {
    return GetTunnelBridgeTransportType(next_tile) == TRANSPORT_ROAD && GetTunnelBridgeDirection(next_tile) == road_dir;
  }
 
  /* If the next tile is a station, allow if it's a road station facing the proper direction. Otherwise return false. */
  if (IsTileType(next_tile, MP_STATION)) {
    /* If the next tile is a road station, allow if it can be entered by the new tunnel/bridge, otherwise disallow. */
    if (IsDriveThroughStopTile(next_tile)) return GetDriveThroughStopAxis(next_tile) == DiagDirToAxis(road_dir);
    if (IsBayRoadStopTile(next_tile)) return GetBayRoadStopDir(next_tile) == ReverseDiagDir(road_dir);
    return false;
  }
 
  /* If the next tile is a road depot, allow if it's facing the right way. */
  if (IsTileType(next_tile, MP_ROAD)) {
    return IsRoadDepot(next_tile) && GetRoadDepotDirection(next_tile) == ReverseDiagDir(road_dir);
  }
 
  /* If the next tile is a railroad track, check if towns are allowed to build level crossings.
   * If level crossing are not allowed, reject the construction. Else allow DoCommand to determine if the rail track is buildable. */
  if (IsTileType(next_tile, MP_RAILWAY) && !_settings_game.economy.allow_town_level_crossings) return false;
 
  /* If a road tile can be built, the construction is allowed. */
  return Command<CMD_BUILD_ROAD>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater}, next_tile, rcmd, rt, DRD_NONE, t->index).Succeeded();
}
static bool CanRoadContinueIntoNextTile(const Town *t, const TileIndex tile, const DiagDirection road_dir) {…}
 
static bool GrowTownWithBridge(const Town *t, const TileIndex tile, const DiagDirection bridge_dir)
{
  assert(bridge_dir < DIAGDIR_END);
 
  const Slope slope = GetTileSlope(tile);
 
  /* Make sure the direction is compatible with the slope.
   * Well we check if the slope has an up bit set in the
   * reverse direction. */
  if (slope != SLOPE_FLAT && slope & InclinedSlope(bridge_dir)) return false;
 
  /* Assure that the bridge is connectable to the start side */
  if (!(GetTownRoadBits(TileAddByDiagDir(tile, ReverseDiagDir(bridge_dir))) & DiagDirToRoadBits(bridge_dir))) return false;
 
  /* We are in the right direction */
  uint bridge_length = 0;       // This value stores the length of the possible bridge
  TileIndex bridge_tile = tile; // Used to store the other waterside
 
  const TileIndexDiff delta = TileOffsByDiagDir(bridge_dir);
 
  /* To prevent really small towns from building disproportionately
   * long bridges, make the max a function of its population. */
  const uint TOWN_BRIDGE_LENGTH_CAP = 11;
  uint base_bridge_length = 5;
  uint max_bridge_length = std::min(t->cache.population / 1000 + base_bridge_length, TOWN_BRIDGE_LENGTH_CAP);
 
  if (slope == SLOPE_FLAT) {
    /* Bridges starting on flat tiles are only allowed when crossing rivers, rails or one-way roads. */
    do {
      if (bridge_length++ >= base_bridge_length) {
        /* Allow to cross rivers, not big lakes, nor large amounts of rails or one-way roads. */
        return false;
      }
      bridge_tile += delta;
    } while (IsValidTile(bridge_tile) && ((IsWaterTile(bridge_tile) && !IsSea(bridge_tile)) || IsPlainRailTile(bridge_tile) || (IsNormalRoadTile(bridge_tile) && GetDisallowedRoadDirections(bridge_tile) != DRD_NONE)));
  } else {
    do {
      if (bridge_length++ >= max_bridge_length) {
        /* Ensure the bridge is not longer than the max allowed length. */
        return false;
      }
      bridge_tile += delta;
    } while (IsValidTile(bridge_tile) && (IsWaterTile(bridge_tile) || IsPlainRailTile(bridge_tile) || (IsNormalRoadTile(bridge_tile) && GetDisallowedRoadDirections(bridge_tile) != DRD_NONE)));
  }
 
  /* Don't allow a bridge where the start and end tiles are adjacent with no span between. */
  if (bridge_length == 1) return false;
 
  /* Make sure the road can be continued past the bridge. At this point, bridge_tile holds the end tile of the bridge. */
  if (!CanRoadContinueIntoNextTile(t, bridge_tile, bridge_dir)) return false;
 
  /* If another parallel bridge exists nearby, this one would be redundant and shouldn't be built. We don't care about flat bridges. */
  if (slope != SLOPE_FLAT) {
    for (auto search : SpiralTileSequence(tile, bridge_length, 0, 0)) {
      /* Only consider bridge head tiles. */
      if (!IsBridgeTile(search)) continue;
 
      /* Only consider road bridges. */
      if (GetTunnelBridgeTransportType(search) != TRANSPORT_ROAD) continue;
 
      /* If the bridge is facing the same direction as the proposed bridge, we've found a redundant bridge. */
      if (GetTileSlope(search) & InclinedSlope(ReverseDiagDir(bridge_dir))) return false;
    }
  }
 
  for (uint8_t times = 0; times <= 22; times++) {
    uint8_t bridge_type = RandomRange(MAX_BRIDGES - 1);
 
    /* Can we actually build the bridge? */
    RoadType rt = GetTownRoadType();
    if (Command<CMD_BUILD_BRIDGE>::Do(CommandFlagsToDCFlags(GetCommandFlags<CMD_BUILD_BRIDGE>()), tile, bridge_tile, TRANSPORT_ROAD, bridge_type, rt).Succeeded()) {
      Command<CMD_BUILD_BRIDGE>::Do(CommandFlagsToDCFlags(GetCommandFlags<CMD_BUILD_BRIDGE>()).Set(DoCommandFlag::Execute), tile, bridge_tile, TRANSPORT_ROAD, bridge_type, rt);
      return true;
    }
  }
  /* Quit if it selecting an appropriate bridge type fails a large number of times. */
  return false;
}
static bool GrowTownWithBridge(const Town *t, const TileIndex tile, const DiagDirection bridge_dir) {…}
 
static bool GrowTownWithTunnel(const Town *t, const TileIndex tile, const DiagDirection tunnel_dir)
{
  assert(tunnel_dir < DIAGDIR_END);
 
  Slope slope = GetTileSlope(tile);
 
  /* Only consider building a tunnel if the starting tile is sloped properly. */
  if (slope != InclinedSlope(tunnel_dir)) return false;
 
  /* Assure that the tunnel is connectable to the start side */
  if (!(GetTownRoadBits(TileAddByDiagDir(tile, ReverseDiagDir(tunnel_dir))) & DiagDirToRoadBits(tunnel_dir))) return false;
 
  const TileIndexDiff delta = TileOffsByDiagDir(tunnel_dir);
  int max_tunnel_length = 0;
 
  /* There are two conditions for building tunnels: Under a mountain and under an obstruction. */
  if (CanRoadContinueIntoNextTile(t, tile, tunnel_dir)) {
    /* Only tunnel under a mountain if the slope is continuous for at least 4 tiles. We want tunneling to be a last resort for large hills. */
    TileIndex slope_tile = tile;
    for (uint8_t tiles = 0; tiles < 4; tiles++) {
      if (!IsValidTile(slope_tile)) return false;
      slope = GetTileSlope(slope_tile);
      if (slope != InclinedSlope(tunnel_dir) && !IsSteepSlope(slope) && !IsSlopeWithOneCornerRaised(slope)) return false;
      slope_tile += delta;
    }
 
    /* More population means longer tunnels, but make sure we can at least cover the smallest mountain which neccesitates tunneling. */
    max_tunnel_length = (t->cache.population / 1000) + 7;
  } else {
    /* When tunneling under an obstruction, the length limit is 5, enough to tunnel under a four-track railway. */
    max_tunnel_length = 5;
  }
 
  uint8_t tunnel_length = 0;
  TileIndex tunnel_tile = tile; // Iteratator to store the other end tile of the tunnel.
 
  /* Find the end tile of the tunnel for length and continuation checks. */
  do {
    if (tunnel_length++ >= max_tunnel_length) return false;
    tunnel_tile += delta;
    /* The tunnel ends when start and end tiles are the same height. */
  } while (IsValidTile(tunnel_tile) && GetTileZ(tile) != GetTileZ(tunnel_tile));
 
  /* Don't allow a tunnel where the start and end tiles are adjacent. */
  if (tunnel_length == 1) return false;
 
  /* Make sure the road can be continued past the tunnel. At this point, tunnel_tile holds the end tile of the tunnel. */
  if (!CanRoadContinueIntoNextTile(t, tunnel_tile, tunnel_dir)) return false;
 
  /* Attempt to build the tunnel. Return false if it fails to let the town build a road instead. */
  RoadType rt = GetTownRoadType();
  if (Command<CMD_BUILD_TUNNEL>::Do(CommandFlagsToDCFlags(GetCommandFlags<CMD_BUILD_TUNNEL>()), tile, TRANSPORT_ROAD, rt).Succeeded()) {
    Command<CMD_BUILD_TUNNEL>::Do(CommandFlagsToDCFlags(GetCommandFlags<CMD_BUILD_TUNNEL>()).Set(DoCommandFlag::Execute), tile, TRANSPORT_ROAD, rt);
    return true;
  }
 
  return false;
}
static bool GrowTownWithTunnel(const Town *t, const TileIndex tile, const DiagDirection tunnel_dir) {…}
 
static inline bool RoadTypesAllowHouseHere(TileIndex t)
{
  static const TileIndexDiffC tiles[] = { {-1, -1}, {-1, 0}, {-1, 1}, {0, -1}, {0, 1}, {1, -1}, {1, 0}, {1, 1} };
  bool allow = false;
 
  for (const auto &ptr : tiles) {
    TileIndex cur_tile = t + ToTileIndexDiff(ptr);
    if (!IsValidTile(cur_tile)) continue;
 
    if (!(IsTileType(cur_tile, MP_ROAD) || IsAnyRoadStopTile(cur_tile))) continue;
    allow = true;
 
    RoadType road_rt = GetRoadTypeRoad(cur_tile);
    RoadType tram_rt = GetRoadTypeTram(cur_tile);
    if (road_rt != INVALID_ROADTYPE && !GetRoadTypeInfo(road_rt)->flags.Test(RoadTypeFlag::NoHouses)) return true;
    if (tram_rt != INVALID_ROADTYPE && !GetRoadTypeInfo(tram_rt)->flags.Test(RoadTypeFlag::NoHouses)) return true;
  }
 
  /* If no road was found surrounding the tile we can allow building the house since there is
   * nothing which forbids it, if a road was found but the execution reached this point, then
   * all the found roads don't allow houses to be built */
  return !allow;
}
static inline bool RoadTypesAllowHouseHere(TileIndex t) {…}
 
static bool TownCanGrowRoad(TileIndex tile)
{
  if (!IsTileType(tile, MP_ROAD)) return true;
 
  /* Allow extending on roadtypes which can be built by town, or if the road type matches the type the town will build. */
  RoadType rt = GetRoadTypeRoad(tile);
  return GetRoadTypeInfo(rt)->flags.Test(RoadTypeFlag::TownBuild) || GetTownRoadType() == rt;
}
static bool TownCanGrowRoad(TileIndex tile) {…}
 
static inline bool TownAllowedToBuildRoads(TownExpandModes modes)
{
  return modes.Test(TownExpandMode::Roads);
}
static inline bool TownAllowedToBuildRoads(TownExpandModes modes) {…}
 
/* The possible states of town growth. */
enum class TownGrowthResult {
  Succeed,
  SearchStopped,
  Continue,
};
 
static TownGrowthResult GrowTownInTile(TileIndex *tile_ptr, RoadBits cur_rb, DiagDirection target_dir, Town *t1, TownExpandModes modes)
{
  RoadBits rcmd = ROAD_NONE;  // RoadBits for the road construction command
  TileIndex tile = *tile_ptr; // The main tile on which we base our growth
 
  assert(tile < Map::Size());
 
  if (cur_rb == ROAD_NONE) {
    /* Tile has no road.
     * We will return TownGrowthResult::SearchStopped to say that this is the last iteration. */
 
    if (!TownAllowedToBuildRoads(modes)) return TownGrowthResult::SearchStopped;
    if (!_settings_game.economy.allow_town_level_crossings && IsTileType(tile, MP_RAILWAY)) return TownGrowthResult::SearchStopped;
 
    /* Remove hills etc */
    if (!_settings_game.construction.build_on_slopes || Chance16(1, 6)) LevelTownLand(tile);
 
    /* Is a road allowed here? */
    switch (t1->layout) {
      default: NOT_REACHED();
 
      case TL_3X3_GRID:
      case TL_2X2_GRID:
        rcmd = GetTownRoadGridElement(t1, tile, target_dir);
        if (rcmd == ROAD_NONE) return TownGrowthResult::SearchStopped;
        break;
 
      case TL_BETTER_ROADS:
      case TL_ORIGINAL:
        if (!IsRoadAllowedHere(t1, tile, target_dir)) return TownGrowthResult::SearchStopped;
 
        DiagDirection source_dir = ReverseDiagDir(target_dir);
 
        if (Chance16(1, 4)) {
          /* Randomize a new target dir */
          do target_dir = RandomDiagDir(); while (target_dir == source_dir);
        }
 
        if (!IsRoadAllowedHere(t1, TileAddByDiagDir(tile, target_dir), target_dir)) {
          /* A road is not allowed to continue the randomized road,
           *  return if the road we're trying to build is curved. */
          if (target_dir != ReverseDiagDir(source_dir)) return TownGrowthResult::SearchStopped;
 
          /* Return if neither side of the new road is a house */
          if (!IsTileType(TileAddByDiagDir(tile, ChangeDiagDir(target_dir, DIAGDIRDIFF_90RIGHT)), MP_HOUSE) &&
              !IsTileType(TileAddByDiagDir(tile, ChangeDiagDir(target_dir, DIAGDIRDIFF_90LEFT)), MP_HOUSE)) {
            return TownGrowthResult::SearchStopped;
          }
 
          /* That means that the road is only allowed if there is a house
           *  at any side of the new road. */
        }
 
        rcmd = DiagDirToRoadBits(target_dir) | DiagDirToRoadBits(source_dir);
        break;
    }
 
  } else if (target_dir < DIAGDIR_END && !(cur_rb & DiagDirToRoadBits(ReverseDiagDir(target_dir)))) {
    if (!TownCanGrowRoad(tile)) return TownGrowthResult::Continue;
 
    if (!TownAllowedToBuildRoads(modes)) return TownGrowthResult::SearchStopped;
 
    /* Continue building on a partial road.
     * Should be always OK, so we only generate
     * the fitting RoadBits */
    switch (t1->layout) {
      default: NOT_REACHED();
 
      case TL_3X3_GRID:
      case TL_2X2_GRID:
        rcmd = GetTownRoadGridElement(t1, tile, target_dir);
        break;
 
      case TL_BETTER_ROADS:
      case TL_ORIGINAL:
        rcmd = DiagDirToRoadBits(ReverseDiagDir(target_dir));
        break;
    }
  } else {
    bool allow_house = true; // Value which decides if we want to construct a house
 
    /* Reached a tunnel/bridge? Then continue at the other side of it, unless
     * it is the starting tile. Half the time, we stay on this side then.*/
    if (IsTileType(tile, MP_TUNNELBRIDGE)) {
      if (GetTunnelBridgeTransportType(tile) == TRANSPORT_ROAD && (target_dir != DIAGDIR_END || Chance16(1, 2))) {
        *tile_ptr = GetOtherTunnelBridgeEnd(tile);
      }
      return TownGrowthResult::Continue;
    }
 
    /* Possibly extend the road in a direction.
     * Randomize a direction and if it has a road, bail out. */
    target_dir = RandomDiagDir();
    RoadBits target_rb = DiagDirToRoadBits(target_dir);
    TileIndex house_tile; // position of a possible house
 
    if (cur_rb & target_rb) {
      /* If it's a road turn possibly build a house in a corner.
       * Use intersection with straight road as an indicator
       * that we randomed corner house position.
       * A turn (and we check for that later) always has only
       * one common bit with a straight road so it has the same
       * chance to be chosen as the house on the side of a road.
       */
      if ((cur_rb & ROAD_X) != target_rb) return TownGrowthResult::Continue;
 
      /* Check whether it is a turn and if so determine
       * position of the corner tile */
      switch (cur_rb) {
        case ROAD_N:
          house_tile = TileAddByDir(tile, DIR_S);
          break;
        case ROAD_S:
          house_tile = TileAddByDir(tile, DIR_N);
          break;
        case ROAD_E:
          house_tile = TileAddByDir(tile, DIR_W);
          break;
        case ROAD_W:
          house_tile = TileAddByDir(tile, DIR_E);
          break;
        default:
          return TownGrowthResult::Continue; // not a turn
      }
      target_dir = DIAGDIR_END;
    } else {
      house_tile = TileAddByDiagDir(tile, target_dir);
    }
 
    /* Don't walk into water. */
    if (HasTileWaterGround(house_tile)) return TownGrowthResult::Continue;
 
    if (!IsValidTile(house_tile)) return TownGrowthResult::Continue;
 
    TownGrowthResult result = TownGrowthResult::Continue;
 
    if (target_dir != DIAGDIR_END && TownAllowedToBuildRoads(modes)) {
      switch (t1->layout) {
        default: NOT_REACHED();
 
        case TL_3X3_GRID: // Use 2x2 grid afterwards!
          if (GrowTownWithExtraHouse(t1, TileAddByDiagDir(house_tile, target_dir), modes)) {
            result = TownGrowthResult::Succeed;
          }
          [[fallthrough]];
 
        case TL_2X2_GRID:
          rcmd = GetTownRoadGridElement(t1, tile, target_dir);
          allow_house = (rcmd & target_rb) == ROAD_NONE;
          break;
 
        case TL_BETTER_ROADS: // Use original afterwards!
          if (GrowTownWithExtraHouse(t1, TileAddByDiagDir(house_tile, target_dir), modes)) {
            result = TownGrowthResult::Succeed;
          }
          [[fallthrough]];
 
        case TL_ORIGINAL:
          /* Allow a house at the edge. 60% chance or
           * always ok if no road allowed. */
          rcmd = target_rb;
          allow_house = (!IsRoadAllowedHere(t1, house_tile, target_dir) || Chance16(6, 10));
          break;
      }
    }
 
    allow_house &= RoadTypesAllowHouseHere(house_tile);
 
    if (allow_house) {
      /* Build a house, but not if there already is a house there. */
      if (!IsTileType(house_tile, MP_HOUSE)) {
        /* Level the land if possible */
        if (Chance16(1, 6)) LevelTownLand(house_tile);
 
        /* And build a house.
         * Set result to -1 if we managed to build it. */
        if (TryBuildTownHouse(t1, house_tile, modes)) {
          result = TownGrowthResult::Succeed;
        }
      }
      return result;
    }
 
    if (!TownCanGrowRoad(tile)) return result;
  }
 
  /* Return if a water tile */
  if (HasTileWaterGround(tile)) return TownGrowthResult::SearchStopped;
 
  /* Make the roads look nicer */
  rcmd = CleanUpRoadBits(tile, rcmd);
  if (rcmd == ROAD_NONE) return TownGrowthResult::SearchStopped;
 
  /* Only use the target direction for bridges and tunnels to ensure they're connected.
   * The target_dir is as computed previously according to town layout, so
   * it will match it perfectly. */
  if (GrowTownWithBridge(t1, tile, target_dir)) {
    return TownGrowthResult::Succeed;
  }
  if (GrowTownWithTunnel(t1, tile, target_dir)) {
    return TownGrowthResult::Succeed;
  }
 
  if (GrowTownWithRoad(t1, tile, rcmd)) {
    return TownGrowthResult::Succeed;
  }
  return TownGrowthResult::SearchStopped;
}
static TownGrowthResult GrowTownInTile(TileIndex *tile_ptr, RoadBits cur_rb, DiagDirection target_dir, Town *t1, TownExpandModes modes) {…}
 
static bool CanFollowRoad(TileIndex tile, DiagDirection dir, TownExpandModes modes)
{
  TileIndex target_tile = tile + TileOffsByDiagDir(dir);
  if (!IsValidTile(target_tile)) return false;
  if (HasTileWaterGround(target_tile)) return false;
 
  RoadBits target_rb = GetTownRoadBits(target_tile);
  if (TownAllowedToBuildRoads(modes)) {
    /* Check whether a road connection exists or can be build. */
    switch (GetTileType(target_tile)) {
      case MP_ROAD:
        return target_rb != ROAD_NONE;
 
      case MP_STATION:
        return IsDriveThroughStopTile(target_tile);
 
      case MP_TUNNELBRIDGE:
        return GetTunnelBridgeTransportType(target_tile) == TRANSPORT_ROAD;
 
      case MP_HOUSE:
      case MP_INDUSTRY:
      case MP_OBJECT:
        return false;
 
      default:
        /* Checked for void and water earlier */
        return true;
    }
  } else {
    /* Check whether a road connection already exists,
     * and it leads somewhere else. */
    RoadBits back_rb = DiagDirToRoadBits(ReverseDiagDir(dir));
    return (target_rb & back_rb) != 0 && (target_rb & ~back_rb) != 0;
  }
}
static bool CanFollowRoad(TileIndex tile, DiagDirection dir, TownExpandModes modes) {…}
 
static bool GrowTownAtRoad(Town *t, TileIndex tile, TownExpandModes modes)
{
  /* Special case.
   * @see GrowTownInTile Check the else if
   */
  DiagDirection target_dir = DIAGDIR_END; // The direction in which we want to extend the town
 
  assert(tile < Map::Size());
 
  /* Number of times to search.
   * Better roads, 2X2 and 3X3 grid grow quite fast so we give
   * them a little handicap. */
  int iterations;
  switch (t->layout) {
    case TL_BETTER_ROADS:
      iterations = 10 + t->cache.num_houses * 2 / 9;
      break;
 
    case TL_3X3_GRID:
    case TL_2X2_GRID:
      iterations = 10 + t->cache.num_houses * 1 / 9;
      break;
 
    default:
      iterations = 10 + t->cache.num_houses * 4 / 9;
      break;
  }
 
  do {
    RoadBits cur_rb = GetTownRoadBits(tile); // The RoadBits of the current tile
 
    /* Try to grow the town from this point */
    switch (GrowTownInTile(&tile, cur_rb, target_dir, t, modes)) {
      case TownGrowthResult::Succeed:
        return true;
      case TownGrowthResult::SearchStopped:
        iterations = 0;
        break;
      default:
        break;
    };
 
    /* Exclude the source position from the bitmask
     * and return if no more road blocks available */
    if (IsValidDiagDirection(target_dir)) cur_rb &= ~DiagDirToRoadBits(ReverseDiagDir(target_dir));
    if (cur_rb == ROAD_NONE) return false;
 
    if (IsTileType(tile, MP_TUNNELBRIDGE)) {
      /* Only build in the direction away from the tunnel or bridge. */
      target_dir = ReverseDiagDir(GetTunnelBridgeDirection(tile));
    } else {
      /* Select a random bit from the blockmask, walk a step
       * and continue the search from there. */
      do {
        if (cur_rb == ROAD_NONE) return false;
        RoadBits target_bits;
        do {
          target_dir = RandomDiagDir();
          target_bits = DiagDirToRoadBits(target_dir);
        } while (!(cur_rb & target_bits));
        cur_rb &= ~target_bits;
      } while (!CanFollowRoad(tile, target_dir, modes));
    }
    tile = TileAddByDiagDir(tile, target_dir);
 
    if (IsTileType(tile, MP_ROAD) && !IsRoadDepot(tile) && HasTileRoadType(tile, RTT_ROAD)) {
      /* Don't allow building over roads of other cities */
      if (IsRoadOwner(tile, RTT_ROAD, OWNER_TOWN) && Town::GetByTile(tile) != t) {
        return false;
      } else if (IsRoadOwner(tile, RTT_ROAD, OWNER_NONE) && _game_mode == GM_EDITOR) {
        /* If we are in the SE, and this road-piece has no town owner yet, it just found an
         * owner :) (happy happy happy road now) */
        SetRoadOwner(tile, RTT_ROAD, OWNER_TOWN);
        SetTownIndex(tile, t->index);
      }
    }
 
    /* Max number of times is checked. */
  } while (--iterations >= 0);
 
  return false;
}
static bool GrowTownAtRoad(Town *t, TileIndex tile, TownExpandModes modes) {…}
 
static RoadBits GenRandomRoadBits()
{
  uint32_t r = Random();
  uint a = GB(r, 0, 2);
  uint b = GB(r, 8, 2);
  if (a == b) b ^= 2;
  return (RoadBits)((ROAD_NW << a) + (ROAD_NW << b));
}
static RoadBits GenRandomRoadBits() {…}
 
static bool GrowTown(Town *t, TownExpandModes modes)
{
  static const TileIndexDiffC _town_coord_mod[] = {
    {-1,  0},
    { 1,  1},
    { 1, -1},
    {-1, -1},
    {-1,  0},
    { 0,  2},
    { 2,  0},
    { 0, -2},
    {-1, -1},
    {-2,  2},
    { 2,  2},
    { 2, -2},
    { 0,  0}
  };
 
  /* Current "company" is a town */
  Backup<CompanyID> cur_company(_current_company, OWNER_TOWN);
 
  TileIndex tile = t->xy; // The tile we are working with ATM
 
  /* Find a road that we can base the construction on. */
  for (const auto &ptr : _town_coord_mod) {
    if (GetTownRoadBits(tile) != ROAD_NONE) {
      bool success = GrowTownAtRoad(t, tile, modes);
      cur_company.Restore();
      return success;
    }
    tile = TileAdd(tile, ToTileIndexDiff(ptr));
  }
 
  /* No road available, try to build a random road block by
   * clearing some land and then building a road there. */
  if (TownAllowedToBuildRoads(modes)) {
    tile = t->xy;
    for (const auto &ptr : _town_coord_mod) {
      /* Only work with plain land that not already has a house */
      if (!IsTileType(tile, MP_HOUSE) && IsTileFlat(tile)) {
        if (Command<CMD_LANDSCAPE_CLEAR>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater}, tile).Succeeded()) {
          RoadType rt = GetTownRoadType();
          Command<CMD_BUILD_ROAD>::Do({DoCommandFlag::Execute, DoCommandFlag::Auto}, tile, GenRandomRoadBits(), rt, DRD_NONE, t->index);
          cur_company.Restore();
          return true;
        }
      }
      tile = TileAdd(tile, ToTileIndexDiff(ptr));
    }
  }
 
  cur_company.Restore();
  return false;
}
static bool GrowTown(Town *t, TownExpandModes modes) {…}
 
void UpdateTownRadius(Town *t)
{
  static const std::array<std::array<uint32_t, NUM_HOUSE_ZONES>, 23> _town_squared_town_zone_radius_data = {{
    {  4,  0,  0,  0,  0}, // 0
    { 16,  0,  0,  0,  0},
    { 25,  0,  0,  0,  0},
    { 36,  0,  0,  0,  0},
    { 49,  0,  4,  0,  0},
    { 64,  0,  4,  0,  0}, // 20
    { 64,  0,  9,  0,  1},
    { 64,  0,  9,  0,  4},
    { 64,  0, 16,  0,  4},
    { 81,  0, 16,  0,  4},
    { 81,  0, 16,  0,  4}, // 40
    { 81,  0, 25,  0,  9},
    { 81, 36, 25,  0,  9},
    { 81, 36, 25, 16,  9},
    { 81, 49,  0, 25,  9},
    { 81, 64,  0, 25,  9}, // 60
    { 81, 64,  0, 36,  9},
    { 81, 64,  0, 36, 16},
    {100, 81,  0, 49, 16},
    {100, 81,  0, 49, 25},
    {121, 81,  0, 49, 25}, // 80
    {121, 81,  0, 49, 25},
    {121, 81,  0, 49, 36}, // 88
  }};
 
  if (t->cache.num_houses < std::size(_town_squared_town_zone_radius_data) * 4) {
    t->cache.squared_town_zone_radius = _town_squared_town_zone_radius_data[t->cache.num_houses / 4];
  } else {
    int mass = t->cache.num_houses / 8;
    /* Actually we are proportional to sqrt() but that's right because we are covering an area.
     * The offsets are to make sure the radii do not decrease in size when going from the table
     * to the calculated value.*/
    t->cache.squared_town_zone_radius[to_underlying(HouseZone::TownEdge)] = mass * 15 - 40;
    t->cache.squared_town_zone_radius[to_underlying(HouseZone::TownOutskirt)] = mass * 9 - 15;
    t->cache.squared_town_zone_radius[to_underlying(HouseZone::TownOuterSuburb)] = 0;
    t->cache.squared_town_zone_radius[to_underlying(HouseZone::TownInnerSuburb)] = mass * 5 - 5;
    t->cache.squared_town_zone_radius[to_underlying(HouseZone::TownCentre)] = mass * 3 + 5;
  }
}
void UpdateTownRadius(Town *t) {…}
 
void UpdateTownMaxPass(Town *t)
{
  for (const CargoSpec *cs : CargoSpec::town_production_cargoes[TPE_PASSENGERS]) {
    uint32_t production = ScaleByCargoScale(t->cache.population >> 3, true);
    if (production == 0) continue;
 
    auto &supplied = t->GetOrCreateCargoSupplied(cs->Index());
    supplied.history[LAST_MONTH].production = production;
  }
 
  for (const CargoSpec *cs : CargoSpec::town_production_cargoes[TPE_MAIL]) {
    uint32_t production = ScaleByCargoScale(t->cache.population >> 4, true);
    if (production == 0) continue;
 
    auto &supplied = t->GetOrCreateCargoSupplied(cs->Index());
    supplied.history[LAST_MONTH].production = production;
  }
}
void UpdateTownMaxPass(Town *t) {…}
 
static void UpdateTownGrowthRate(Town *t);
static void UpdateTownGrowth(Town *t);
 
static void DoCreateTown(Town *t, TileIndex tile, uint32_t townnameparts, TownSize size, bool city, TownLayout layout, bool manual)
{
  AutoRestoreBackup backup(_generating_town, true);
 
  t->xy = tile;
  t->cache.num_houses = 0;
  t->time_until_rebuild = 10;
  UpdateTownRadius(t);
  t->flags = 0;
  t->cache.population = 0;
  InitializeBuildingCounts(t);
  /* Spread growth across ticks so even if there are many
   * similar towns they're unlikely to grow all in one tick */
  t->grow_counter = t->index % Ticks::TOWN_GROWTH_TICKS;
  t->growth_rate = TownTicksToGameTicks(250);
  t->show_zone = false;
 
  _town_kdtree.Insert(t->index);
 
  /* Set the default cargo requirement for town growth */
  switch (_settings_game.game_creation.landscape) {
    case LandscapeType::Arctic:
      if (FindFirstCargoWithTownAcceptanceEffect(TAE_FOOD) != nullptr) t->goal[TAE_FOOD] = TOWN_GROWTH_WINTER;
      break;
 
    case LandscapeType::Tropic:
      if (FindFirstCargoWithTownAcceptanceEffect(TAE_FOOD) != nullptr) t->goal[TAE_FOOD] = TOWN_GROWTH_DESERT;
      if (FindFirstCargoWithTownAcceptanceEffect(TAE_WATER) != nullptr) t->goal[TAE_WATER] = TOWN_GROWTH_DESERT;
      break;
 
    default:
      break;
  }
 
  t->fund_buildings_months = 0;
 
  for (uint i = 0; i != MAX_COMPANIES; i++) t->ratings[i] = RATING_INITIAL;
 
  t->have_ratings = {};
  t->exclusivity = CompanyID::Invalid();
  t->exclusive_counter = 0;
  t->statues = {};
 
  {
    TownNameParams tnp(_settings_game.game_creation.town_name);
    t->townnamegrfid = tnp.grfid;
    t->townnametype = tnp.type;
  }
  t->townnameparts = townnameparts;
 
  t->InitializeLayout(layout);
 
  t->larger_town = city;
 
  int x = (int)size * 16 + 3;
  if (size == TSZ_RANDOM) x = (Random() & 0xF) + 8;
  /* Don't create huge cities when founding town in-game */
  if (city && (!manual || _game_mode == GM_EDITOR)) x *= _settings_game.economy.initial_city_size;
 
  t->cache.num_houses += x;
  UpdateTownRadius(t);
 
  int i = x * 4;
  do {
    GrowTown(t, {TownExpandMode::Buildings, TownExpandMode::Roads});
  } while (--i);
 
  t->UpdateVirtCoord();
  InvalidateWindowData(WC_TOWN_DIRECTORY, 0, TDIWD_FORCE_REBUILD);
 
  t->cache.num_houses -= x;
  UpdateTownRadius(t);
  UpdateTownGrowthRate(t);
  UpdateTownMaxPass(t);
  UpdateAirportsNoise();
}
static void DoCreateTown(Town *t, TileIndex tile, uint32_t townnameparts, TownSize size, bool city, TownLayout layout, bool manual) {…}
 
static CommandCost TownCanBePlacedHere(TileIndex tile)
{
  /* Check if too close to the edge of map */
  if (DistanceFromEdge(tile) < 12) {
    return CommandCost(STR_ERROR_TOO_CLOSE_TO_EDGE_OF_MAP_SUB);
  }
 
  /* Check distance to all other towns. */
  if (IsCloseToTown(tile, 20)) {
    return CommandCost(STR_ERROR_TOO_CLOSE_TO_ANOTHER_TOWN);
  }
 
  /* Can only build on clear flat areas, possibly with trees. */
  if ((!IsTileType(tile, MP_CLEAR) && !IsTileType(tile, MP_TREES)) || !IsTileFlat(tile)) {
    return CommandCost(STR_ERROR_SITE_UNSUITABLE);
  }
 
  return CommandCost(EXPENSES_OTHER);
}
static CommandCost TownCanBePlacedHere(TileIndex tile) {…}
 
static bool IsUniqueTownName(const std::string &name)
{
  for (const Town *t : Town::Iterate()) {
    if (!t->name.empty() && t->name == name) return false;
  }
 
  return true;
}
static bool IsUniqueTownName(const std::string &name) {…}
 
std::tuple<CommandCost, Money, TownID> CmdFoundTown(DoCommandFlags flags, TileIndex tile, TownSize size, bool city, TownLayout layout, bool random_location, uint32_t townnameparts, const std::string &text)
{
  TownNameParams par(_settings_game.game_creation.town_name);
 
  if (size >= TSZ_END) return { CMD_ERROR, 0, TownID::Invalid() };
  if (layout >= NUM_TLS) return { CMD_ERROR, 0, TownID::Invalid() };
 
  /* Some things are allowed only in the scenario editor and for game scripts. */
  if (_game_mode != GM_EDITOR && _current_company != OWNER_DEITY) {
    if (_settings_game.economy.found_town == TF_FORBIDDEN) return { CMD_ERROR, 0, TownID::Invalid() };
    if (size == TSZ_LARGE) return { CMD_ERROR, 0, TownID::Invalid() };
    if (random_location) return { CMD_ERROR, 0, TownID::Invalid() };
    if (_settings_game.economy.found_town != TF_CUSTOM_LAYOUT && layout != _settings_game.economy.town_layout) {
      return { CMD_ERROR, 0, TownID::Invalid() };
    }
  } else if (_current_company == OWNER_DEITY && random_location) {
    /* Random parameter is not allowed for Game Scripts. */
    return { CMD_ERROR, 0, TownID::Invalid() };
  }
 
  if (text.empty()) {
    /* If supplied name is empty, townnameparts has to generate unique automatic name */
    if (!VerifyTownName(townnameparts, &par)) return { CommandCost(STR_ERROR_NAME_MUST_BE_UNIQUE), 0, TownID::Invalid() };
  } else {
    /* If name is not empty, it has to be unique custom name */
    if (Utf8StringLength(text) >= MAX_LENGTH_TOWN_NAME_CHARS) return { CMD_ERROR, 0, TownID::Invalid() };
    if (!IsUniqueTownName(text)) return { CommandCost(STR_ERROR_NAME_MUST_BE_UNIQUE), 0, TownID::Invalid() };
  }
 
  /* Allocate town struct */
  if (!Town::CanAllocateItem()) return { CommandCost(STR_ERROR_TOO_MANY_TOWNS), 0, TownID::Invalid() };
 
  if (!random_location) {
    CommandCost ret = TownCanBePlacedHere(tile);
    if (ret.Failed()) return { ret, 0, TownID::Invalid() };
  }
 
  static const uint8_t price_mult[][TSZ_RANDOM + 1] = {{ 15, 25, 40, 25 }, { 20, 35, 55, 35 }};
  /* multidimensional arrays have to have defined length of non-first dimension */
  static_assert(lengthof(price_mult[0]) == 4);
 
  CommandCost cost(EXPENSES_OTHER, _price[PR_BUILD_TOWN]);
  uint8_t mult = price_mult[city][size];
 
  cost.MultiplyCost(mult);
 
  /* Create the town */
  TownID new_town = TownID::Invalid();
  if (flags.Test(DoCommandFlag::Execute)) {
    if (cost.GetCost() > GetAvailableMoneyForCommand()) {
      return { CommandCost(EXPENSES_OTHER), cost.GetCost(), TownID::Invalid() };
    }
 
    Backup<bool> old_generating_world(_generating_world, true);
    UpdateNearestTownForRoadTiles(true);
    Town *t;
    if (random_location) {
      t = CreateRandomTown(20, townnameparts, size, city, layout);
    } else {
      t = new Town(tile);
      DoCreateTown(t, tile, townnameparts, size, city, layout, true);
    }
 
    UpdateNearestTownForRoadTiles(false);
    old_generating_world.Restore();
 
    if (t == nullptr) return { CommandCost(STR_ERROR_NO_SPACE_FOR_TOWN), 0, TownID::Invalid() };
 
    new_town = t->index;
 
    if (!text.empty()) {
      t->name = text;
      t->UpdateVirtCoord();
    }
 
    if (_game_mode != GM_EDITOR) {
      /* 't' can't be nullptr since 'random' is false outside scenedit */
      assert(!random_location);
 
      if (_current_company == OWNER_DEITY) {
        AddTileNewsItem(GetEncodedString(STR_NEWS_NEW_TOWN_UNSPONSORED, t->index), NewsType::IndustryOpen, tile);
      } else {
        std::string company_name = GetString(STR_COMPANY_NAME, _current_company);
        AddTileNewsItem(GetEncodedString(STR_NEWS_NEW_TOWN, company_name, t->index), NewsType::IndustryOpen, tile);
      }
      AI::BroadcastNewEvent(new ScriptEventTownFounded(t->index));
      Game::NewEvent(new ScriptEventTownFounded(t->index));
    }
  }
  return { cost, 0, new_town };
}
std::tuple<CommandCost, Money, TownID> CmdFoundTown(DoCommandFlags flags, TileIndex tile, TownSize size, bool city, TownLayout layout, bool random_location, uint32_t townnameparts, const std::string &text) {…}
 
static TileIndex AlignTileToGrid(TileIndex tile, TownLayout layout)
{
  switch (layout) {
    case TL_2X2_GRID: return TileXY(TileX(tile) - TileX(tile) % 3, TileY(tile) - TileY(tile) % 3);
    case TL_3X3_GRID: return TileXY(TileX(tile) & ~3, TileY(tile) & ~3);
    default:          return tile;
  }
}
static TileIndex AlignTileToGrid(TileIndex tile, TownLayout layout) {…}
 
static bool IsTileAlignedToGrid(TileIndex tile, TownLayout layout)
{
  switch (layout) {
    case TL_2X2_GRID: return TileX(tile) % 3 == 0 && TileY(tile) % 3 == 0;
    case TL_3X3_GRID: return TileX(tile) % 4 == 0 && TileY(tile) % 4 == 0;
    default:          return true;
  }
}
static bool IsTileAlignedToGrid(TileIndex tile, TownLayout layout) {…}
 
static TileIndex FindNearestGoodCoastalTownSpot(TileIndex tile, TownLayout layout)
{
  for (auto coast : SpiralTileSequence(tile, 40)) {
    /* Find nearest land tile */
    if (!IsTileType(tile, MP_CLEAR)) continue;
 
    TileIndex furthest = INVALID_TILE;
    uint max_dist = 0;
    for (auto test : SpiralTileSequence(coast, 10)) {
      if (!IsTileType(test, MP_CLEAR) || !IsTileFlat(test) || !IsTileAlignedToGrid(test, layout)) continue;
 
      uint dist = GetClosestWaterDistance(test, true);
      if (dist > max_dist) {
        furthest = test;
        max_dist = dist;
      }
    }
    return furthest;
  }
 
  /* if we get here just give up */
  return INVALID_TILE;
}
static TileIndex FindNearestGoodCoastalTownSpot(TileIndex tile, TownLayout layout) {…}
 
HouseZones GetClimateMaskForLandscape()
{
  switch (_settings_game.game_creation.landscape) {
    case LandscapeType::Temperate: return HouseZone::ClimateTemperate;
    case LandscapeType::Arctic: return {HouseZone::ClimateSubarcticAboveSnow, HouseZone::ClimateSubarcticBelowSnow};
    case LandscapeType::Tropic: return HouseZone::ClimateSubtropic;
    case LandscapeType::Toyland: return HouseZone::ClimateToyland;
    default: NOT_REACHED();
  }
}
HouseZones GetClimateMaskForLandscape() {…}
 
static Town *CreateRandomTown(uint attempts, uint32_t townnameparts, TownSize size, bool city, TownLayout layout)
{
  assert(_game_mode == GM_EDITOR || _generating_world); // These are the preconditions for CMD_DELETE_TOWN
 
  if (!Town::CanAllocateItem()) return nullptr;
 
  do {
    /* Generate a tile index not too close from the edge */
    TileIndex tile = AlignTileToGrid(RandomTile(), layout);
 
    /* if we tried to place the town on water, slide it over onto
     * the nearest likely-looking spot */
    if (IsTileType(tile, MP_WATER)) {
      tile = FindNearestGoodCoastalTownSpot(tile, layout);
      if (tile == INVALID_TILE) continue;
    }
 
    /* Make sure town can be placed here */
    if (TownCanBePlacedHere(tile).Failed()) continue;
 
    /* Allocate a town struct */
    Town *t = new Town(tile);
 
    DoCreateTown(t, tile, townnameparts, size, city, layout, false);
 
    /* if the population is still 0 at the point, then the
     * placement is so bad it couldn't grow at all */
    if (t->cache.population > 0) return t;
 
    Backup<CompanyID> cur_company(_current_company, OWNER_TOWN);
    [[maybe_unused]] CommandCost rc = Command<CMD_DELETE_TOWN>::Do(DoCommandFlag::Execute, t->index);
    cur_company.Restore();
    assert(rc.Succeeded());
 
    /* We already know that we can allocate a single town when
     * entering this function. However, we create and delete
     * a town which "resets" the allocation checks. As such we
     * need to check again when assertions are enabled. */
    assert(Town::CanAllocateItem());
  } while (--attempts != 0);
 
  return nullptr;
}
static Town *CreateRandomTown(uint attempts, uint32_t townnameparts, TownSize size, bool city, TownLayout layout) {…}
 
uint GetDefaultTownsForMapSize()
{
  static const uint8_t num_initial_towns[4] = {5, 11, 23, 46};  // very low, low, normal, high
  if (_settings_game.difficulty.number_towns == static_cast<uint>(CUSTOM_TOWN_NUMBER_DIFFICULTY)) {
    return _settings_newgame.game_creation.custom_town_number;
  }
  return Map::ScaleBySize(num_initial_towns[_settings_game.difficulty.number_towns]);
}
uint GetDefaultTownsForMapSize() {…}
 
bool GenerateTowns(TownLayout layout, std::optional<uint> number)
{
  uint current_number = 0;
  uint total;
  if (number.has_value()) {
    total = number.value();
  } else if (_settings_game.difficulty.number_towns == static_cast<uint>(CUSTOM_TOWN_NUMBER_DIFFICULTY)) {
    total = GetDefaultTownsForMapSize();
  } else {
    total = GetDefaultTownsForMapSize() + (Random() & 7);
  }
 
  total = std::min<uint>(TownPool::MAX_SIZE, total);
  uint32_t townnameparts;
  TownNames town_names;
 
  SetGeneratingWorldProgress(GWP_TOWN, total);
 
  /* Pre-populate the town names list with the names of any towns already on the map */
  for (const Town *town : Town::Iterate()) {
    town_names.insert(town->GetCachedName());
  }
 
  /* Randomised offset for city status. This means with e.g. 1-in-4 towns being cities, a map with 10 towns
   * may have 2 or 3 cities, instead of always 3. */
  uint city_random_offset = _settings_game.economy.larger_towns == 0 ? 0 : (Random() % _settings_game.economy.larger_towns);
 
  /* First attempt will be made at creating the suggested number of towns.
   * Note that this is really a suggested value, not a required one.
   * We would not like the system to lock up just because the user wanted 100 cities on a 64*64 map, would we? */
  do {
    bool city = (_settings_game.economy.larger_towns != 0 && ((city_random_offset + current_number) % _settings_game.economy.larger_towns) == 0);
    IncreaseGeneratingWorldProgress(GWP_TOWN);
    /* Get a unique name for the town. */
    if (!GenerateTownName(_random, &townnameparts, &town_names)) continue;
    /* try 20 times to create a random-sized town for the first loop. */
    if (CreateRandomTown(20, townnameparts, TSZ_RANDOM, city, layout) != nullptr) current_number++; // If creation was successful, raise a flag.
  } while (--total);
 
  town_names.clear();
 
  /* Build the town k-d tree again to make sure it's well balanced */
  RebuildTownKdtree();
 
  if (current_number != 0) return true;
 
  /* If current_number is still zero at this point, it means that not a single town has been created.
   * So give it a last try, but now more aggressive */
  if (GenerateTownName(_random, &townnameparts) &&
      CreateRandomTown(10000, townnameparts, TSZ_RANDOM, _settings_game.economy.larger_towns != 0, layout) != nullptr) {
    return true;
  }
 
  /* If there are no towns at all and we are generating new game, bail out */
  if (Town::GetNumItems() == 0 && _game_mode != GM_EDITOR) {
    ShowErrorMessage(GetEncodedString(STR_ERROR_COULD_NOT_CREATE_TOWN), {}, WL_CRITICAL);
  }
 
  return false;  // we are still without a town? we failed, simply
}
bool GenerateTowns(TownLayout layout, std::optional<uint> number) {…}
 
 
HouseZone GetTownRadiusGroup(const Town *t, TileIndex tile)
{
  uint dist = DistanceSquare(tile, t->xy);
 
  if (t->fund_buildings_months != 0 && dist <= 25) return HouseZone::TownCentre;
 
  HouseZone smallest = HouseZone::TownEdge;
  for (HouseZone i : HZ_ZONE_ALL) {
    if (dist < t->cache.squared_town_zone_radius[to_underlying(i)]) smallest = i;
  }
 
  return smallest;
}
HouseZone GetTownRadiusGroup(const Town *t, TileIndex tile) {…}
 
static inline void ClearMakeHouseTile(TileIndex tile, Town *t, uint8_t counter, uint8_t stage, HouseID type, uint8_t random_bits, bool is_protected)
{
  [[maybe_unused]] CommandCost cc = Command<CMD_LANDSCAPE_CLEAR>::Do({DoCommandFlag::Execute, DoCommandFlag::Auto, DoCommandFlag::NoWater}, tile);
  assert(cc.Succeeded());
 
  IncreaseBuildingCount(t, type);
  MakeHouseTile(tile, t->index, counter, stage, type, random_bits, is_protected);
  if (HouseSpec::Get(type)->building_flags.Test(BuildingFlag::IsAnimated)) AddAnimatedTile(tile, false);
 
  MarkTileDirtyByTile(tile);
}
static inline void ClearMakeHouseTile(TileIndex tile, Town *t, uint8_t counter, uint8_t stage, HouseID type, uint8_t random_bits, bool is_protected) {…}
 
 
static void MakeTownHouse(TileIndex tile, Town *t, uint8_t counter, uint8_t stage, HouseID type, uint8_t random_bits, bool is_protected)
{
  BuildingFlags size = HouseSpec::Get(type)->building_flags;
 
  ClearMakeHouseTile(tile, t, counter, stage, type, random_bits, is_protected);
  if (size.Any(BUILDING_2_TILES_Y))   ClearMakeHouseTile(tile + TileDiffXY(0, 1), t, counter, stage, ++type, random_bits, is_protected);
  if (size.Any(BUILDING_2_TILES_X))   ClearMakeHouseTile(tile + TileDiffXY(1, 0), t, counter, stage, ++type, random_bits, is_protected);
  if (size.Any(BUILDING_HAS_4_TILES)) ClearMakeHouseTile(tile + TileDiffXY(1, 1), t, counter, stage, ++type, random_bits, is_protected);
 
  ForAllStationsAroundTiles(TileArea(tile, size.Any(BUILDING_2_TILES_X) ? 2 : 1, size.Any(BUILDING_2_TILES_Y) ? 2 : 1), [t](Station *st, TileIndex) {
    t->stations_near.insert(st);
    return true;
  });
}
static void MakeTownHouse(TileIndex tile, Town *t, uint8_t counter, uint8_t stage, HouseID type, uint8_t random_bits, bool is_protected) {…}
 
 
static inline bool CanBuildHouseHere(TileIndex tile, bool noslope)
{
  /* cannot build on these slopes... */
  Slope slope = GetTileSlope(tile);
  if ((noslope && slope != SLOPE_FLAT) || IsSteepSlope(slope)) return false;
 
  /* at least one RoadTypes allow building the house here? */
  if (!RoadTypesAllowHouseHere(tile)) return false;
 
  /* building under a bridge? */
  if (IsBridgeAbove(tile)) return false;
 
  /* can we clear the land? */
  return Command<CMD_LANDSCAPE_CLEAR>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater}, tile).Succeeded();
}
static inline bool CanBuildHouseHere(TileIndex tile, bool noslope) {…}
 
 
static inline bool CheckBuildHouseSameZ(TileIndex tile, int z, bool noslope)
{
  if (!CanBuildHouseHere(tile, noslope)) return false;
 
  /* if building on slopes is allowed, there will be flattening foundation (to tile max z) */
  if (GetTileMaxZ(tile) != z) return false;
 
  return true;
}
static inline bool CheckBuildHouseSameZ(TileIndex tile, int z, bool noslope) {…}
 
 
static bool CheckFree2x2Area(TileIndex tile, int z, bool noslope)
{
  /* we need to check this tile too because we can be at different tile now */
  if (!CheckBuildHouseSameZ(tile, z, noslope)) return false;
 
  for (DiagDirection d = DIAGDIR_SE; d < DIAGDIR_END; d++) {
    tile += TileOffsByDiagDir(d);
    if (!CheckBuildHouseSameZ(tile, z, noslope)) return false;
  }
 
  return true;
}
static bool CheckFree2x2Area(TileIndex tile, int z, bool noslope) {…}
 
 
static inline bool TownLayoutAllowsHouseHere(Town *t, TileIndex tile, TownExpandModes modes)
{
  if (!modes.Test(TownExpandMode::Buildings)) return false;
 
  /* Allow towns everywhere when we don't build roads */
  if (!TownAllowedToBuildRoads(modes)) return true;
 
  TileIndexDiffC grid_pos = TileIndexToTileIndexDiffC(t->xy, tile);
 
  switch (t->layout) {
    case TL_2X2_GRID:
      if ((grid_pos.x % 3) == 0 || (grid_pos.y % 3) == 0) return false;
      break;
 
    case TL_3X3_GRID:
      if ((grid_pos.x % 4) == 0 || (grid_pos.y % 4) == 0) return false;
      break;
 
    default:
      break;
  }
 
  return true;
}
static inline bool TownLayoutAllowsHouseHere(Town *t, TileIndex tile, TownExpandModes modes) {…}
 
 
static inline bool TownLayoutAllows2x2HouseHere(Town *t, TileIndex tile, TownExpandModes modes)
{
  if (!modes.Test(TownExpandMode::Buildings)) return false;
 
  /* Allow towns everywhere when we don't build roads */
  if (!TownAllowedToBuildRoads(modes)) return true;
 
  /* Compute relative position of tile. (Positive offsets are towards north) */
  TileIndexDiffC grid_pos = TileIndexToTileIndexDiffC(t->xy, tile);
 
  switch (t->layout) {
    case TL_2X2_GRID:
      grid_pos.x %= 3;
      grid_pos.y %= 3;
      if ((grid_pos.x != 2 && grid_pos.x != -1) ||
        (grid_pos.y != 2 && grid_pos.y != -1)) return false;
      break;
 
    case TL_3X3_GRID:
      if ((grid_pos.x & 3) < 2 || (grid_pos.y & 3) < 2) return false;
      break;
 
    default:
      break;
  }
 
  return true;
}
static inline bool TownLayoutAllows2x2HouseHere(Town *t, TileIndex tile, TownExpandModes modes) {…}
 
 
static bool CheckTownBuild2House(TileIndex *tile, Town *t, int maxz, bool noslope, DiagDirection second, TownExpandModes modes)
{
  /* 'tile' is already checked in BuildTownHouse() - CanBuildHouseHere() and slope test */
 
  TileIndex tile2 = *tile + TileOffsByDiagDir(second);
  if (TownLayoutAllowsHouseHere(t, tile2, modes) && CheckBuildHouseSameZ(tile2, maxz, noslope)) return true;
 
  tile2 = *tile + TileOffsByDiagDir(ReverseDiagDir(second));
  if (TownLayoutAllowsHouseHere(t, tile2, modes) && CheckBuildHouseSameZ(tile2, maxz, noslope)) {
    *tile = tile2;
    return true;
  }
 
  return false;
}
static bool CheckTownBuild2House(TileIndex *tile, Town *t, int maxz, bool noslope, DiagDirection second, TownExpandModes modes) {…}
 
 
static bool CheckTownBuild2x2House(TileIndex *tile, Town *t, int maxz, bool noslope, TownExpandModes modes)
{
  TileIndex tile2 = *tile;
 
  for (DiagDirection d = DIAGDIR_SE;; d++) { // 'd' goes through DIAGDIR_SE, DIAGDIR_SW, DIAGDIR_NW, DIAGDIR_END
    if (TownLayoutAllows2x2HouseHere(t, tile2, modes) && CheckFree2x2Area(tile2, maxz, noslope)) {
      *tile = tile2;
      return true;
    }
    if (d == DIAGDIR_END) break;
    tile2 += TileOffsByDiagDir(ReverseDiagDir(d)); // go clockwise
  }
 
  return false;
}
static bool CheckTownBuild2x2House(TileIndex *tile, Town *t, int maxz, bool noslope, TownExpandModes modes) {…}
 
static void BuildTownHouse(Town *t, TileIndex tile, const HouseSpec *hs, HouseID house, uint8_t random_bits, bool house_completed, bool is_protected)
{
  /* build the house */
  t->cache.num_houses++;
 
  uint8_t construction_counter = 0;
  uint8_t construction_stage = 0;
 
  if (_generating_world || _game_mode == GM_EDITOR || house_completed) {
    uint32_t construction_random = Random();
 
    construction_stage = TOWN_HOUSE_COMPLETED;
    if (_generating_world && !hs->extra_flags.Test(HouseExtraFlag::BuildingIsHistorical) && Chance16(1, 7)) construction_stage = GB(construction_random, 0, 2);
 
    if (construction_stage == TOWN_HOUSE_COMPLETED) {
      ChangePopulation(t, hs->population);
    } else {
      construction_counter = GB(construction_random, 2, 2);
    }
  }
 
  MakeTownHouse(tile, t, construction_counter, construction_stage, house, random_bits, is_protected);
  UpdateTownRadius(t);
  UpdateTownGrowthRate(t);
 
  BuildingFlags size = hs->building_flags;
 
  TriggerHouseAnimation_ConstructionStageChanged(tile, true);
  if (size.Any(BUILDING_2_TILES_Y)) TriggerHouseAnimation_ConstructionStageChanged(tile + TileDiffXY(0, 1), true);
  if (size.Any(BUILDING_2_TILES_X)) TriggerHouseAnimation_ConstructionStageChanged(tile + TileDiffXY(1, 0), true);
  if (size.Any(BUILDING_HAS_4_TILES)) TriggerHouseAnimation_ConstructionStageChanged(tile + TileDiffXY(1, 1), true);
}
static void BuildTownHouse(Town *t, TileIndex tile, const HouseSpec *hs, HouseID house, uint8_t random_bits, bool house_completed, bool is_protected) {…}
 
static bool TryBuildTownHouse(Town *t, TileIndex tile, TownExpandModes modes)
{
  /* forbidden building here by town layout */
  if (!TownLayoutAllowsHouseHere(t, tile, modes)) return false;
 
  /* no house allowed at all, bail out */
  if (!CanBuildHouseHere(tile, false)) return false;
 
  Slope slope = GetTileSlope(tile);
  int maxz = GetTileMaxZ(tile);
 
  /* Get the town zone type of the current tile, as well as the climate.
   * This will allow to easily compare with the specs of the new house to build */
  HouseZones zones = GetTownRadiusGroup(t, tile);
 
  switch (_settings_game.game_creation.landscape) {
    case LandscapeType::Temperate: zones.Set(HouseZone::ClimateTemperate); break;
    case LandscapeType::Arctic: zones.Set(maxz > HighestSnowLine() ? HouseZone::ClimateSubarcticAboveSnow : HouseZone::ClimateSubarcticBelowSnow); break;
    case LandscapeType::Tropic: zones.Set(HouseZone::ClimateSubtropic); break;
    case LandscapeType::Toyland: zones.Set(HouseZone::ClimateToyland); break;
  }
 
  /* bits 0-4 are used
   * bits 11-15 are used
   * bits 5-10 are not used. */
  static std::vector<std::pair<HouseID, uint>> probs;
  probs.clear();
 
  uint probability_max = 0;
 
  /* Generate a list of all possible houses that can be built. */
  for (const auto &hs : HouseSpec::Specs()) {
    /* Verify that the candidate house spec matches the current tile status */
    if (!hs.building_availability.All(zones) || !hs.enabled || hs.grf_prop.override_id != INVALID_HOUSE_ID) continue;
 
    /* Don't let these counters overflow. Global counters are 32bit, there will never be that many houses. */
    if (hs.class_id != HOUSE_NO_CLASS) {
      /* id_count is always <= class_count, so it doesn't need to be checked */
      if (t->cache.building_counts.class_count[hs.class_id] == UINT16_MAX) continue;
    } else {
      /* If the house has no class, check id_count instead */
      if (t->cache.building_counts.id_count[hs.Index()] == UINT16_MAX) continue;
    }
 
    uint cur_prob = hs.probability;
    probability_max += cur_prob;
    probs.emplace_back(hs.Index(), cur_prob);
  }
 
  TileIndex base_tile = tile;
 
  while (probability_max > 0) {
    /* Building a multitile building can change the location of tile.
     * The building would still be built partially on that tile, but
     * its northern tile would be elsewhere. However, if the callback
     * fails we would be basing further work from the changed tile.
     * So a next 1x1 tile building could be built on the wrong tile. */
    tile = base_tile;
 
    uint r = RandomRange(probability_max);
    uint i;
    for (i = 0; i < probs.size(); i++) {
      if (probs[i].second > r) break;
      r -= probs[i].second;
    }
 
    HouseID house = probs[i].first;
    probability_max -= probs[i].second;
 
    /* remove tested house from the set */
    probs[i] = probs.back();
    probs.pop_back();
 
    const HouseSpec *hs = HouseSpec::Get(house);
 
    if (!_generating_world && _game_mode != GM_EDITOR && hs->extra_flags.Test(HouseExtraFlag::BuildingIsHistorical)) {
      continue;
    }
 
    if (TimerGameCalendar::year < hs->min_year || TimerGameCalendar::year > hs->max_year) continue;
 
    /* Special houses that there can be only one of. */
    uint oneof = 0;
 
    if (hs->building_flags.Test(BuildingFlag::IsChurch)) {
      SetBit(oneof, TOWN_HAS_CHURCH);
    } else if (hs->building_flags.Test(BuildingFlag::IsStadium)) {
      SetBit(oneof, TOWN_HAS_STADIUM);
    }
 
    if (t->flags & oneof) continue;
 
    /* Make sure there is no slope? */
    bool noslope = hs->building_flags.Test(BuildingFlag::NotSloped);
    if (noslope && slope != SLOPE_FLAT) continue;
 
    if (hs->building_flags.Test(BuildingFlag::Size2x2)) {
      if (!CheckTownBuild2x2House(&tile, t, maxz, noslope, modes)) continue;
    } else if (hs->building_flags.Test(BuildingFlag::Size2x1)) {
      if (!CheckTownBuild2House(&tile, t, maxz, noslope, DIAGDIR_SW, modes)) continue;
    } else if (hs->building_flags.Test(BuildingFlag::Size1x2)) {
      if (!CheckTownBuild2House(&tile, t, maxz, noslope, DIAGDIR_SE, modes)) continue;
    } else {
      /* 1x1 house checks are already done */
    }
 
    uint8_t random_bits = Random();
 
    if (hs->callback_mask.Test(HouseCallbackMask::AllowConstruction)) {
      uint16_t callback_res = GetHouseCallback(CBID_HOUSE_ALLOW_CONSTRUCTION, 0, 0, house, t, tile, {}, true, random_bits);
      if (callback_res != CALLBACK_FAILED && !Convert8bitBooleanCallback(hs->grf_prop.grffile, CBID_HOUSE_ALLOW_CONSTRUCTION, callback_res)) continue;
    }
 
    /* Special houses that there can be only one of. */
    t->flags |= oneof;
 
    BuildTownHouse(t, tile, hs, house, random_bits, false, hs->extra_flags.Test(HouseExtraFlag::BuildingIsProtected));
 
    return true;
  }
 
  return false;
}
static bool TryBuildTownHouse(Town *t, TileIndex tile, TownExpandModes modes) {…}
 
CommandCost CmdPlaceHouse(DoCommandFlags flags, TileIndex tile, HouseID house, bool is_protected)
{
  if (_game_mode != GM_EDITOR && _settings_game.economy.place_houses == PH_FORBIDDEN) return CMD_ERROR;
 
  if (Town::GetNumItems() == 0) return CommandCost(STR_ERROR_MUST_FOUND_TOWN_FIRST);
 
  if (static_cast<size_t>(house) >= HouseSpec::Specs().size()) return CMD_ERROR;
  const HouseSpec *hs = HouseSpec::Get(house);
  if (!hs->enabled) return CMD_ERROR;
 
  Town *t = ClosestTownFromTile(tile, UINT_MAX);
 
  /* cannot build on these slopes... */
  Slope slope = GetTileSlope(tile);
  if (IsSteepSlope(slope)) return CommandCost(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
 
  /* building under a bridge? */
  if (IsBridgeAbove(tile)) return CommandCost(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
 
  /* can we clear the land? */
  CommandCost cost = Command<CMD_LANDSCAPE_CLEAR>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater}, tile);
  if (!cost.Succeeded()) return cost;
 
  int maxz = GetTileMaxZ(tile);
 
  /* Make sure there is no slope? */
  bool noslope = hs->building_flags.Test(BuildingFlag::NotSloped);
  if (noslope && slope != SLOPE_FLAT) return CommandCost(STR_ERROR_FLAT_LAND_REQUIRED);
 
  TileArea ta = tile;
  if (hs->building_flags.Test(BuildingFlag::Size2x2)) ta.Add(TileAddXY(tile, 1, 1));
  if (hs->building_flags.Test(BuildingFlag::Size2x1)) ta.Add(TileAddByDiagDir(tile, DIAGDIR_SW));
  if (hs->building_flags.Test(BuildingFlag::Size1x2)) ta.Add(TileAddByDiagDir(tile, DIAGDIR_SE));
 
  /* Check additional tiles covered by this house. */
  for (const TileIndex &subtile : ta) {
    cost = Command<CMD_LANDSCAPE_CLEAR>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater}, subtile);
    if (!cost.Succeeded()) return cost;
 
    if (!CheckBuildHouseSameZ(subtile, maxz, noslope)) return CommandCost(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
  }
 
  if (flags.Test(DoCommandFlag::Execute)) {
    bool house_completed = _settings_game.economy.place_houses == PH_ALLOWED_CONSTRUCTED;
    BuildTownHouse(t, tile, hs, house, Random(), house_completed, is_protected);
  }
 
  return CommandCost();
}
CommandCost CmdPlaceHouse(DoCommandFlags flags, TileIndex tile, HouseID house, bool is_protected) {…}
 
static void DoClearTownHouseHelper(TileIndex tile, Town *t, HouseID house)
{
  assert(IsTileType(tile, MP_HOUSE));
  DecreaseBuildingCount(t, house);
  DoClearSquare(tile);
 
  DeleteNewGRFInspectWindow(GSF_HOUSES, tile.base());
}
static void DoClearTownHouseHelper(TileIndex tile, Town *t, HouseID house) {…}
 
TileIndexDiff GetHouseNorthPart(HouseID &house)
{
  if (house >= 3) { // house id 0,1,2 MUST be single tile houses, or this code breaks.
    if (HouseSpec::Get(house - 1)->building_flags.Test(BuildingFlag::Size2x1)) {
      house--;
      return TileDiffXY(-1, 0);
    } else if (HouseSpec::Get(house - 1)->building_flags.Any(BUILDING_2_TILES_Y)) {
      house--;
      return TileDiffXY(0, -1);
    } else if (HouseSpec::Get(house - 2)->building_flags.Any(BUILDING_HAS_4_TILES)) {
      house -= 2;
      return TileDiffXY(-1, 0);
    } else if (HouseSpec::Get(house - 3)->building_flags.Any(BUILDING_HAS_4_TILES)) {
      house -= 3;
      return TileDiffXY(-1, -1);
    }
  }
  return TileDiffXY(0, 0);
}
TileIndexDiff GetHouseNorthPart(HouseID &house) {…}
 
void ClearTownHouse(Town *t, TileIndex tile)
{
  assert(IsTileType(tile, MP_HOUSE));
 
  HouseID house = GetHouseType(tile);
 
  /* The northernmost tile of the house is the main house. */
  tile += GetHouseNorthPart(house);
 
  const HouseSpec *hs = HouseSpec::Get(house);
 
  /* Remove population from the town if the house is finished. */
  if (IsHouseCompleted(tile)) {
    ChangePopulation(t, -hs->population);
  }
 
  t->cache.num_houses--;
 
  /* Clear flags for houses that only may exist once/town. */
  if (hs->building_flags.Test(BuildingFlag::IsChurch)) {
    ClrBit(t->flags, TOWN_HAS_CHURCH);
  } else if (hs->building_flags.Test(BuildingFlag::IsStadium)) {
    ClrBit(t->flags, TOWN_HAS_STADIUM);
  }
 
  /* Do the actual clearing of tiles */
  DoClearTownHouseHelper(tile, t, house);
  if (hs->building_flags.Any(BUILDING_2_TILES_Y))   DoClearTownHouseHelper(tile + TileDiffXY(0, 1), t, ++house);
  if (hs->building_flags.Any(BUILDING_2_TILES_X))   DoClearTownHouseHelper(tile + TileDiffXY(1, 0), t, ++house);
  if (hs->building_flags.Any(BUILDING_HAS_4_TILES)) DoClearTownHouseHelper(tile + TileDiffXY(1, 1), t, ++house);
 
  RemoveNearbyStations(t, tile, hs->building_flags);
 
  UpdateTownRadius(t);
}
void ClearTownHouse(Town *t, TileIndex tile) {…}
 
CommandCost CmdRenameTown(DoCommandFlags flags, TownID town_id, const std::string &text)
{
  Town *t = Town::GetIfValid(town_id);
  if (t == nullptr) return CMD_ERROR;
 
  bool reset = text.empty();
 
  if (!reset) {
    if (Utf8StringLength(text) >= MAX_LENGTH_TOWN_NAME_CHARS) return CMD_ERROR;
    if (!IsUniqueTownName(text)) return CommandCost(STR_ERROR_NAME_MUST_BE_UNIQUE);
  }
 
  if (flags.Test(DoCommandFlag::Execute)) {
    t->cached_name.clear();
    if (reset) {
      t->name.clear();
    } else {
      t->name = text;
    }
 
    t->UpdateVirtCoord();
    InvalidateWindowData(WC_TOWN_DIRECTORY, 0, TDIWD_FORCE_RESORT);
    ClearAllStationCachedNames();
    ClearAllIndustryCachedNames();
    UpdateAllStationVirtCoords();
  }
  return CommandCost();
}
CommandCost CmdRenameTown(DoCommandFlags flags, TownID town_id, const std::string &text) {…}
 
const CargoSpec *FindFirstCargoWithTownAcceptanceEffect(TownAcceptanceEffect effect)
{
  for (const CargoSpec *cs : CargoSpec::Iterate()) {
    if (cs->town_acceptance_effect == effect) return cs;
  }
  return nullptr;
}
const CargoSpec *FindFirstCargoWithTownAcceptanceEffect(TownAcceptanceEffect effect) {…}
 
CommandCost CmdTownCargoGoal(DoCommandFlags flags, TownID town_id, TownAcceptanceEffect tae, uint32_t goal)
{
  if (_current_company != OWNER_DEITY) return CMD_ERROR;
 
  if (tae < TAE_BEGIN || tae >= TAE_END) return CMD_ERROR;
 
  Town *t = Town::GetIfValid(town_id);
  if (t == nullptr) return CMD_ERROR;
 
  /* Validate if there is a cargo which is the requested TownEffect */
  const CargoSpec *cargo = FindFirstCargoWithTownAcceptanceEffect(tae);
  if (cargo == nullptr) return CMD_ERROR;
 
  if (flags.Test(DoCommandFlag::Execute)) {
    t->goal[tae] = goal;
    UpdateTownGrowth(t);
    InvalidateWindowData(WC_TOWN_VIEW, town_id);
  }
 
  return CommandCost();
}
CommandCost CmdTownCargoGoal(DoCommandFlags flags, TownID town_id, TownAcceptanceEffect tae, uint32_t goal) {…}
 
CommandCost CmdTownSetText(DoCommandFlags flags, TownID town_id, const EncodedString &text)
{
  if (_current_company != OWNER_DEITY) return CMD_ERROR;
  Town *t = Town::GetIfValid(town_id);
  if (t == nullptr) return CMD_ERROR;
 
  if (flags.Test(DoCommandFlag::Execute)) {
    t->text.clear();
    if (!text.empty()) t->text = text;
    InvalidateWindowData(WC_TOWN_VIEW, town_id);
  }
 
  return CommandCost();
}
CommandCost CmdTownSetText(DoCommandFlags flags, TownID town_id, const EncodedString &text) {…}
 
CommandCost CmdTownGrowthRate(DoCommandFlags flags, TownID town_id, uint16_t growth_rate)
{
  if (_current_company != OWNER_DEITY) return CMD_ERROR;
 
  Town *t = Town::GetIfValid(town_id);
  if (t == nullptr) return CMD_ERROR;
 
  if (flags.Test(DoCommandFlag::Execute)) {
    if (growth_rate == 0) {
      /* Just clear the flag, UpdateTownGrowth will determine a proper growth rate */
      ClrBit(t->flags, TOWN_CUSTOM_GROWTH);
    } else {
      uint old_rate = t->growth_rate;
      if (t->grow_counter >= old_rate) {
        /* This also catches old_rate == 0 */
        t->grow_counter = growth_rate;
      } else {
        /* Scale grow_counter, so half finished houses stay half finished */
        t->grow_counter = t->grow_counter * growth_rate / old_rate;
      }
      t->growth_rate = growth_rate;
      SetBit(t->flags, TOWN_CUSTOM_GROWTH);
    }
    UpdateTownGrowth(t);
    InvalidateWindowData(WC_TOWN_VIEW, town_id);
  }
 
  return CommandCost();
}
CommandCost CmdTownGrowthRate(DoCommandFlags flags, TownID town_id, uint16_t growth_rate) {…}
 
CommandCost CmdTownRating(DoCommandFlags flags, TownID town_id, CompanyID company_id, int16_t rating)
{
  if (_current_company != OWNER_DEITY) return CMD_ERROR;
 
  Town *t = Town::GetIfValid(town_id);
  if (t == nullptr) return CMD_ERROR;
 
  if (!Company::IsValidID(company_id)) return CMD_ERROR;
 
  int16_t new_rating = Clamp(rating, RATING_MINIMUM, RATING_MAXIMUM);
  if (flags.Test(DoCommandFlag::Execute)) {
    t->ratings[company_id] = new_rating;
    InvalidateWindowData(WC_TOWN_AUTHORITY, town_id);
  }
 
  return CommandCost();
}
CommandCost CmdTownRating(DoCommandFlags flags, TownID town_id, CompanyID company_id, int16_t rating) {…}
 
CommandCost CmdExpandTown(DoCommandFlags flags, TownID town_id, uint32_t grow_amount, TownExpandModes modes)
{
  if (_game_mode != GM_EDITOR && _current_company != OWNER_DEITY) return CMD_ERROR;
  if (modes.None()) return CMD_ERROR;
  Town *t = Town::GetIfValid(town_id);
  if (t == nullptr) return CMD_ERROR;
 
  if (flags.Test(DoCommandFlag::Execute)) {
    /* The more houses, the faster we grow */
    if (grow_amount == 0) {
      uint amount = RandomRange(ClampTo<uint16_t>(t->cache.num_houses / 10)) + 3;
      t->cache.num_houses += amount;
      UpdateTownRadius(t);
 
      uint n = amount * 10;
      do GrowTown(t, modes); while (--n);
 
      t->cache.num_houses -= amount;
    } else {
      for (; grow_amount > 0; grow_amount--) {
        /* Try several times to grow, as we are really suppose to grow */
        for (uint i = 0; i < 25; i++) if (GrowTown(t, modes)) break;
      }
    }
    UpdateTownRadius(t);
 
    UpdateTownMaxPass(t);
  }
 
  return CommandCost();
}
CommandCost CmdExpandTown(DoCommandFlags flags, TownID town_id, uint32_t grow_amount, TownExpandModes modes) {…}
 
CommandCost CmdDeleteTown(DoCommandFlags flags, TownID town_id)
{
  if (_game_mode != GM_EDITOR && !_generating_world) return CMD_ERROR;
  Town *t = Town::GetIfValid(town_id);
  if (t == nullptr) return CMD_ERROR;
 
  /* Stations refer to towns. */
  for (const Station *st : Station::Iterate()) {
    if (st->town == t) {
      /* Non-oil rig stations are always a problem. */
      if (!st->facilities.Test(StationFacility::Airport) || st->airport.type != AT_OILRIG) return CMD_ERROR;
      /* We can only automatically delete oil rigs *if* there's no vehicle on them. */
      CommandCost ret = Command<CMD_LANDSCAPE_CLEAR>::Do(flags, st->airport.tile);
      if (ret.Failed()) return ret;
    }
  }
 
  /* Waypoints refer to towns. */
  for (const Waypoint *wp : Waypoint::Iterate()) {
    if (wp->town == t) return CMD_ERROR;
  }
 
  /* Depots refer to towns. */
  for (const Depot *d : Depot::Iterate()) {
    if (d->town == t) return CMD_ERROR;
  }
 
  /* Check all tiles for town ownership. First check for bridge tiles, as
   * these do not directly have an owner so we need to check adjacent
   * tiles. This won't work correctly in the same loop if the adjacent
   * tile was already deleted earlier in the loop. */
  for (const auto current_tile : Map::Iterate()) {
    if (IsTileType(current_tile, MP_TUNNELBRIDGE) && TestTownOwnsBridge(current_tile, t)) {
      CommandCost ret = Command<CMD_LANDSCAPE_CLEAR>::Do(flags, current_tile);
      if (ret.Failed()) return ret;
    }
  }
 
  /* Check all remaining tiles for town ownership. */
  for (const auto current_tile : Map::Iterate()) {
    bool try_clear = false;
    switch (GetTileType(current_tile)) {
      case MP_ROAD:
        try_clear = HasTownOwnedRoad(current_tile) && GetTownIndex(current_tile) == t->index;
        break;
 
      case MP_HOUSE:
        try_clear = GetTownIndex(current_tile) == t->index;
        break;
 
      case MP_INDUSTRY:
        try_clear = Industry::GetByTile(current_tile)->town == t;
        break;
 
      case MP_OBJECT:
        if (Town::GetNumItems() == 1) {
          /* No towns will be left, remove it! */
          try_clear = true;
        } else {
          Object *o = Object::GetByTile(current_tile);
          if (o->town == t) {
            if (o->type == OBJECT_STATUE) {
              /* Statue... always remove. */
              try_clear = true;
            } else {
              /* Tell to find a new town. */
              if (flags.Test(DoCommandFlag::Execute)) o->town = nullptr;
            }
          }
        }
        break;
 
      default:
        break;
    }
    if (try_clear) {
      CommandCost ret = Command<CMD_LANDSCAPE_CLEAR>::Do(flags, current_tile);
      if (ret.Failed()) return ret;
    }
  }
 
  /* The town destructor will delete the other things related to the town. */
  if (flags.Test(DoCommandFlag::Execute)) {
    _town_kdtree.Remove(t->index);
    if (t->cache.sign.kdtree_valid) _viewport_sign_kdtree.Remove(ViewportSignKdtreeItem::MakeTown(t->index));
    delete t;
  }
 
  return CommandCost();
}
CommandCost CmdDeleteTown(DoCommandFlags flags, TownID town_id) {…}
 
uint8_t GetTownActionCost(TownAction action)
{
  static const uint8_t town_action_costs[] = {
    2, 4, 9, 35, 48, 53, 117, 175
  };
  static_assert(std::size(town_action_costs) == to_underlying(TownAction::End));
 
  assert(to_underlying(action) < std::size(town_action_costs));
  return town_action_costs[to_underlying(action)];
}
uint8_t GetTownActionCost(TownAction action) {…}
 
static CommandCost TownActionAdvertiseSmall(Town *t, DoCommandFlags flags)
{
  if (flags.Test(DoCommandFlag::Execute)) {
    ModifyStationRatingAround(t->xy, _current_company, 0x40, 10);
  }
  return CommandCost();
}
static CommandCost TownActionAdvertiseSmall(Town *t, DoCommandFlags flags) {…}
 
static CommandCost TownActionAdvertiseMedium(Town *t, DoCommandFlags flags)
{
  if (flags.Test(DoCommandFlag::Execute)) {
    ModifyStationRatingAround(t->xy, _current_company, 0x70, 15);
  }
  return CommandCost();
}
static CommandCost TownActionAdvertiseMedium(Town *t, DoCommandFlags flags) {…}
 
static CommandCost TownActionAdvertiseLarge(Town *t, DoCommandFlags flags)
{
  if (flags.Test(DoCommandFlag::Execute)) {
    ModifyStationRatingAround(t->xy, _current_company, 0xA0, 20);
  }
  return CommandCost();
}
static CommandCost TownActionAdvertiseLarge(Town *t, DoCommandFlags flags) {…}
 
static CommandCost TownActionRoadRebuild(Town *t, DoCommandFlags flags)
{
  /* Check if the company is allowed to fund new roads. */
  if (!_settings_game.economy.fund_roads) return CMD_ERROR;
 
  if (flags.Test(DoCommandFlag::Execute)) {
    t->road_build_months = 6;
 
    std::string company_name = GetString(STR_COMPANY_NAME, _current_company);
 
    AddNewsItem(
      GetEncodedString(TimerGameEconomy::UsingWallclockUnits() ? STR_NEWS_ROAD_REBUILDING_MINUTES : STR_NEWS_ROAD_REBUILDING_MONTHS, t->index, company_name),
      NewsType::General, NewsStyle::Normal, {}, t->index);
    AI::BroadcastNewEvent(new ScriptEventRoadReconstruction(_current_company, t->index));
    Game::NewEvent(new ScriptEventRoadReconstruction(_current_company, t->index));
  }
  return CommandCost();
}
static CommandCost TownActionRoadRebuild(Town *t, DoCommandFlags flags) {…}
 
static bool CheckClearTile(TileIndex tile)
{
  Backup<CompanyID> cur_company(_current_company, OWNER_NONE);
  CommandCost r = Command<CMD_LANDSCAPE_CLEAR>::Do({}, tile);
  cur_company.Restore();
  return r.Succeeded();
}
static bool CheckClearTile(TileIndex tile) {…}
 
static CommandCost TownActionBuildStatue(Town *t, DoCommandFlags flags)
{
  if (!Object::CanAllocateItem()) return CommandCost(STR_ERROR_TOO_MANY_OBJECTS);
 
  static const int STATUE_NUMBER_INNER_TILES = 25; // Number of tiles int the center of the city, where we try to protect houses.
 
  TileIndex best_position = INVALID_TILE; 
  uint tile_count = 0; 
  for (auto tile : SpiralTileSequence(t->xy, 9)) {
    tile_count++;
 
    /* Statues can be build on slopes, just like houses. Only the steep slopes is a no go. */
    if (IsSteepSlope(GetTileSlope(tile))) continue;
    /* Don't build statues under bridges. */
    if (IsBridgeAbove(tile)) continue;
 
    /* A clear-able open space is always preferred. */
    if ((IsTileType(tile, MP_CLEAR) || IsTileType(tile, MP_TREES)) && CheckClearTile(tile)) {
      best_position = tile;
      break;
    }
 
    bool house = IsTileType(tile, MP_HOUSE);
 
    /* Searching inside the inner circle. */
    if (tile_count <= STATUE_NUMBER_INNER_TILES) {
      /* Save first house in inner circle. */
      if (house && best_position == INVALID_TILE && CheckClearTile(tile)) {
        best_position = tile;
      }
 
      /* If we have reached the end of the inner circle, and have a saved house, terminate the search. */
      if (tile_count == STATUE_NUMBER_INNER_TILES && best_position != INVALID_TILE) break;
    }
 
    /* Searching outside the circle, just pick the first possible spot. */
    if (!house || !CheckClearTile(tile)) continue;
    best_position = tile;
    break;
  }
  if (best_position == INVALID_TILE) return CommandCost(STR_ERROR_STATUE_NO_SUITABLE_PLACE);
 
  if (flags.Test(DoCommandFlag::Execute)) {
    Backup<CompanyID> cur_company(_current_company, OWNER_NONE);
    Command<CMD_LANDSCAPE_CLEAR>::Do(DoCommandFlag::Execute, best_position);
    cur_company.Restore();
    BuildObject(OBJECT_STATUE, best_position, _current_company, t);
    t->statues.Set(_current_company); // Once found and built, "inform" the Town.
    MarkTileDirtyByTile(best_position);
  }
  return CommandCost();
}
static CommandCost TownActionBuildStatue(Town *t, DoCommandFlags flags) {…}
 
static CommandCost TownActionFundBuildings(Town *t, DoCommandFlags flags)
{
  /* Check if it's allowed to buy the rights */
  if (!_settings_game.economy.fund_buildings) return CMD_ERROR;
 
  if (flags.Test(DoCommandFlag::Execute)) {
    /* And grow for 3 months */
    t->fund_buildings_months = 3;
 
    /* Enable growth (also checking GameScript's opinion) */
    UpdateTownGrowth(t);
 
    /* Build a new house, but add a small delay to make sure
     * that spamming funding doesn't let town grow any faster
     * than 1 house per 2 * TOWN_GROWTH_TICKS ticks.
     * Also emulate original behaviour when town was only growing in
     * TOWN_GROWTH_TICKS intervals, to make sure that it's not too
     * tick-perfect and gives player some time window where they can
     * spam funding with the exact same efficiency.
     */
    t->grow_counter = std::min<uint16_t>(t->grow_counter, 2 * Ticks::TOWN_GROWTH_TICKS - (t->growth_rate - t->grow_counter) % Ticks::TOWN_GROWTH_TICKS);
 
    SetWindowDirty(WC_TOWN_VIEW, t->index);
  }
  return CommandCost();
}
static CommandCost TownActionFundBuildings(Town *t, DoCommandFlags flags) {…}
 
static CommandCost TownActionBuyRights(Town *t, DoCommandFlags flags)
{
  /* Check if it's allowed to buy the rights */
  if (!_settings_game.economy.exclusive_rights) return CMD_ERROR;
  if (t->exclusivity != CompanyID::Invalid()) return CMD_ERROR;
 
  if (flags.Test(DoCommandFlag::Execute)) {
    t->exclusive_counter = 12;
    t->exclusivity = _current_company;
 
    ModifyStationRatingAround(t->xy, _current_company, 130, 17);
 
    SetWindowClassesDirty(WC_STATION_VIEW);
 
    /* Spawn news message */
    auto cni = std::make_unique<CompanyNewsInformation>(STR_NEWS_EXCLUSIVE_RIGHTS_TITLE, Company::Get(_current_company));
    EncodedString message = GetEncodedString(TimerGameEconomy::UsingWallclockUnits() ? STR_NEWS_EXCLUSIVE_RIGHTS_DESCRIPTION_MINUTES : STR_NEWS_EXCLUSIVE_RIGHTS_DESCRIPTION_MONTHS, t->index, cni->company_name);
    AddNewsItem(std::move(message),
      NewsType::General, NewsStyle::Company, {}, t->index, {}, std::move(cni));
    AI::BroadcastNewEvent(new ScriptEventExclusiveTransportRights(_current_company, t->index));
    Game::NewEvent(new ScriptEventExclusiveTransportRights(_current_company, t->index));
  }
  return CommandCost();
}
static CommandCost TownActionBuyRights(Town *t, DoCommandFlags flags) {…}
 
static CommandCost TownActionBribe(Town *t, DoCommandFlags flags)
{
  if (flags.Test(DoCommandFlag::Execute)) {
    if (Chance16(1, 14)) {
      /* set as unwanted for 6 months */
      t->unwanted[_current_company] = 6;
 
      /* set all close by station ratings to 0 */
      for (Station *st : Station::Iterate()) {
        if (st->town == t && st->owner == _current_company) {
          for (GoodsEntry &ge : st->goods) ge.rating = 0;
        }
      }
 
      /* only show error message to the executing player. All errors are handled command.c
       * but this is special, because it can only 'fail' on a DoCommandFlag::Execute */
      if (IsLocalCompany()) ShowErrorMessage(GetEncodedString(STR_ERROR_BRIBE_FAILED), {}, WL_INFO);
 
      /* decrease by a lot!
       * ChangeTownRating is only for stuff in demolishing. Bribe failure should
       * be independent of any cheat settings
       */
      if (t->ratings[_current_company] > RATING_BRIBE_DOWN_TO) {
        t->ratings[_current_company] = RATING_BRIBE_DOWN_TO;
        SetWindowDirty(WC_TOWN_AUTHORITY, t->index);
      }
    } else {
      ChangeTownRating(t, RATING_BRIBE_UP_STEP, RATING_BRIBE_MAXIMUM, DoCommandFlag::Execute);
      if (t->exclusivity != _current_company && t->exclusivity != CompanyID::Invalid()) {
        t->exclusivity = CompanyID::Invalid();
        t->exclusive_counter = 0;
      }
    }
  }
  return CommandCost();
}
static CommandCost TownActionBribe(Town *t, DoCommandFlags flags) {…}
 
typedef CommandCost TownActionProc(Town *t, DoCommandFlags flags);
static TownActionProc * const _town_action_proc[] = {
  TownActionAdvertiseSmall,
  TownActionAdvertiseMedium,
  TownActionAdvertiseLarge,
  TownActionRoadRebuild,
  TownActionBuildStatue,
  TownActionFundBuildings,
  TownActionBuyRights,
  TownActionBribe
};
static_assert(std::size(_town_action_proc) == to_underlying(TownAction::End));
 
TownActions GetMaskOfTownActions(CompanyID cid, const Town *t)
{
  TownActions buttons{};
 
  /* Spectators and unwanted have no options */
  if (cid != COMPANY_SPECTATOR && !(_settings_game.economy.bribe && t->unwanted[cid])) {
 
    /* Actions worth more than this are not able to be performed */
    Money avail = GetAvailableMoney(cid);
 
    /* Check the action bits for validity and
     * if they are valid add them */
    for (TownAction cur = {}; cur != TownAction::End; ++cur) {
 
      /* Is the company prohibited from bribing ? */
      if (cur == TownAction::Bribe) {
        /* Company can't bribe if setting is disabled */
        if (!_settings_game.economy.bribe) continue;
        /* Company can bribe if another company has exclusive transport rights,
         * or its standing with the town is less than outstanding. */
        if (t->ratings[cid] >= RATING_BRIBE_MAXIMUM) {
          if (t->exclusivity == _current_company) continue;
          if (t->exclusive_counter == 0) continue;
        }
      }
 
      /* Is the company not able to buy exclusive rights ? */
      if (cur == TownAction::BuyRights && (!_settings_game.economy.exclusive_rights || t->exclusive_counter != 0)) continue;
 
      /* Is the company not able to fund buildings ? */
      if (cur == TownAction::FundBuildings && !_settings_game.economy.fund_buildings) continue;
 
      /* Is the company not able to fund local road reconstruction? */
      if (cur == TownAction::RoadRebuild && !_settings_game.economy.fund_roads) continue;
 
      /* Is the company not able to build a statue ? */
      if (cur == TownAction::BuildStatue && t->statues.Test(cid)) continue;
 
      if (avail >= GetTownActionCost(cur) * _price[PR_TOWN_ACTION] >> 8) {
        buttons.Set(cur);
      }
    }
  }
 
  return buttons;
}
TownActions GetMaskOfTownActions(CompanyID cid, const Town *t) {…}
 
CommandCost CmdDoTownAction(DoCommandFlags flags, TownID town_id, TownAction action)
{
  Town *t = Town::GetIfValid(town_id);
  if (t == nullptr || to_underlying(action) >= std::size(_town_action_proc)) return CMD_ERROR;
 
  if (!GetMaskOfTownActions(_current_company, t).Test(action)) return CMD_ERROR;
 
  CommandCost cost(EXPENSES_OTHER, _price[PR_TOWN_ACTION] * GetTownActionCost(action) >> 8);
 
  CommandCost ret = _town_action_proc[to_underlying(action)](t, flags);
  if (ret.Failed()) return ret;
 
  if (flags.Test(DoCommandFlag::Execute)) {
    SetWindowDirty(WC_TOWN_AUTHORITY, town_id);
  }
 
  return cost;
}
CommandCost CmdDoTownAction(DoCommandFlags flags, TownID town_id, TownAction action) {…}
 
template <typename Func>
static void ForAllStationsNearTown(Town *t, Func func)
{
  /* Ideally the search radius should be close to the actual town zone 0 radius.
   * The true radius is not stored or calculated anywhere, only the squared radius. */
  /* The efficiency of this search might be improved for large towns and many stations on the map,
   * by using an integer square root approximation giving a value not less than the true square root. */
  uint search_radius = t->cache.squared_town_zone_radius[to_underlying(HouseZone::TownEdge)] / 2;
  ForAllStationsRadius(t->xy, search_radius, [&](const Station * st) {
    if (DistanceSquare(st->xy, t->xy) <= t->cache.squared_town_zone_radius[to_underlying(HouseZone::TownEdge)]) {
      func(st);
    }
  });
}
 
static void UpdateTownRating(Town *t)
{
  /* Increase company ratings if they're low */
  for (const Company *c : Company::Iterate()) {
    if (t->ratings[c->index] < RATING_GROWTH_MAXIMUM) {
      t->ratings[c->index] = std::min((int)RATING_GROWTH_MAXIMUM, t->ratings[c->index] + RATING_GROWTH_UP_STEP);
    }
  }
 
  ForAllStationsNearTown(t, [&](const Station *st) {
    if (st->time_since_load <= 20 || st->time_since_unload <= 20) {
      if (Company::IsValidID(st->owner)) {
        int new_rating = t->ratings[st->owner] + RATING_STATION_UP_STEP;
        t->ratings[st->owner] = std::min<int>(new_rating, INT16_MAX); // do not let it overflow
      }
    } else {
      if (Company::IsValidID(st->owner)) {
        int new_rating = t->ratings[st->owner] + RATING_STATION_DOWN_STEP;
        t->ratings[st->owner] = std::max(new_rating, INT16_MIN);
      }
    }
  });
 
  /* clamp all ratings to valid values */
  for (uint i = 0; i < MAX_COMPANIES; i++) {
    t->ratings[i] = Clamp(t->ratings[i], RATING_MINIMUM, RATING_MAXIMUM);
  }
 
  SetWindowDirty(WC_TOWN_AUTHORITY, t->index);
}
static void UpdateTownRating(Town *t) {…}
 
 
static void UpdateTownGrowCounter(Town *t, uint16_t prev_growth_rate)
{
  if (t->growth_rate == TOWN_GROWTH_RATE_NONE) return;
  if (prev_growth_rate == TOWN_GROWTH_RATE_NONE) {
    t->grow_counter = std::min<uint16_t>(t->growth_rate, t->grow_counter);
    return;
  }
  t->grow_counter = RoundDivSU((uint32_t)t->grow_counter * (t->growth_rate + 1), prev_growth_rate + 1);
}
static void UpdateTownGrowCounter(Town *t, uint16_t prev_growth_rate) {…}
 
static int CountActiveStations(Town *t)
{
  int n = 0;
  ForAllStationsNearTown(t, [&](const Station * st) {
    if (st->time_since_load <= 20 || st->time_since_unload <= 20) {
      n++;
    }
  });
  return n;
}
static int CountActiveStations(Town *t) {…}
 
static uint GetNormalGrowthRate(Town *t)
{
  static const uint16_t _grow_count_values[2][6] = {
    { 120, 120, 120, 100,  80,  60 }, // Fund new buildings has been activated
    { 320, 420, 300, 220, 160, 100 }  // Normal values
  };
 
  int n = CountActiveStations(t);
  uint16_t m = _grow_count_values[t->fund_buildings_months != 0 ? 0 : 1][std::min(n, 5)];
 
  uint growth_multiplier = _settings_game.economy.town_growth_rate != 0 ? _settings_game.economy.town_growth_rate - 1 : 1;
 
  m >>= growth_multiplier;
  if (t->larger_town) m /= 2;
 
  return TownTicksToGameTicks(m / (t->cache.num_houses / 50 + 1));
}
static uint GetNormalGrowthRate(Town *t) {…}
 
static void UpdateTownGrowthRate(Town *t)
{
  if (HasBit(t->flags, TOWN_CUSTOM_GROWTH)) return;
  uint old_rate = t->growth_rate;
  t->growth_rate = GetNormalGrowthRate(t);
  UpdateTownGrowCounter(t, old_rate);
  SetWindowDirty(WC_TOWN_VIEW, t->index);
}
static void UpdateTownGrowthRate(Town *t) {…}
 
static void UpdateTownGrowth(Town *t)
{
  UpdateTownGrowthRate(t);
 
  ClrBit(t->flags, TOWN_IS_GROWING);
  SetWindowDirty(WC_TOWN_VIEW, t->index);
 
  if (_settings_game.economy.town_growth_rate == 0 && t->fund_buildings_months == 0) return;
 
  if (t->fund_buildings_months == 0) {
    /* Check if all goals are reached for this town to grow (given we are not funding it) */
    for (int i = TAE_BEGIN; i < TAE_END; i++) {
      switch (t->goal[i]) {
        case TOWN_GROWTH_WINTER:
          if (TileHeight(t->xy) >= GetSnowLine() && t->received[i].old_act == 0 && t->cache.population > 90) return;
          break;
        case TOWN_GROWTH_DESERT:
          if (GetTropicZone(t->xy) == TROPICZONE_DESERT && t->received[i].old_act == 0 && t->cache.population > 60) return;
          break;
        default:
          if (t->goal[i] > t->received[i].old_act) return;
          break;
      }
    }
  }
 
  if (HasBit(t->flags, TOWN_CUSTOM_GROWTH)) {
    if (t->growth_rate != TOWN_GROWTH_RATE_NONE) SetBit(t->flags, TOWN_IS_GROWING);
    SetWindowDirty(WC_TOWN_VIEW, t->index);
    return;
  }
 
  if (t->fund_buildings_months == 0 && CountActiveStations(t) == 0 && !Chance16(1, 12)) return;
 
  SetBit(t->flags, TOWN_IS_GROWING);
  SetWindowDirty(WC_TOWN_VIEW, t->index);
}
static void UpdateTownGrowth(Town *t) {…}
 
CommandCost CheckIfAuthorityAllowsNewStation(TileIndex tile, DoCommandFlags flags)
{
  /* The required rating is hardcoded to RATING_VERYPOOR (see below), not the authority attitude setting, so we can bail out like this. */
  if (_settings_game.difficulty.town_council_tolerance == TOWN_COUNCIL_PERMISSIVE) return CommandCost();
 
  if (!Company::IsValidID(_current_company) || flags.Test(DoCommandFlag::NoTestTownRating)) return CommandCost();
 
  Town *t = ClosestTownFromTile(tile, _settings_game.economy.dist_local_authority);
  if (t == nullptr) return CommandCost();
 
  if (t->ratings[_current_company] > RATING_VERYPOOR) return CommandCost();
 
  return CommandCostWithParam(STR_ERROR_LOCAL_AUTHORITY_REFUSES_TO_ALLOW_THIS, t->index);
}
CommandCost CheckIfAuthorityAllowsNewStation(TileIndex tile, DoCommandFlags flags) {…}
 
Town *CalcClosestTownFromTile(TileIndex tile, uint threshold)
{
  if (Town::GetNumItems() == 0) return nullptr;
 
  TownID tid = _town_kdtree.FindNearest(TileX(tile), TileY(tile));
  Town *town = Town::Get(tid);
  if (DistanceManhattan(tile, town->xy) < threshold) return town;
  return nullptr;
}
Town *CalcClosestTownFromTile(TileIndex tile, uint threshold) {…}
 
Town *ClosestTownFromTile(TileIndex tile, uint threshold)
{
  switch (GetTileType(tile)) {
    case MP_ROAD:
      if (IsRoadDepot(tile)) return CalcClosestTownFromTile(tile, threshold);
 
      if (!HasTownOwnedRoad(tile)) {
        TownID tid = GetTownIndex(tile);
 
        if (tid == TownID::Invalid()) {
          /* in the case we are generating "many random towns", this value may be TownID::Invalid() */
          if (_generating_world) return CalcClosestTownFromTile(tile, threshold);
          assert(Town::GetNumItems() == 0);
          return nullptr;
        }
 
        assert(Town::IsValidID(tid));
        Town *town = Town::Get(tid);
 
        if (DistanceManhattan(tile, town->xy) >= threshold) town = nullptr;
 
        return town;
      }
      [[fallthrough]];
 
    case MP_HOUSE:
      return Town::GetByTile(tile);
 
    default:
      return CalcClosestTownFromTile(tile, threshold);
  }
}
Town *ClosestTownFromTile(TileIndex tile, uint threshold) {…}
 
static bool _town_rating_test = false; 
static std::map<const Town *, int> _town_test_ratings; 
 
void SetTownRatingTestMode(bool mode)
{
  static int ref_count = 0; // Number of times test-mode is switched on.
  if (mode) {
    if (ref_count == 0) {
      _town_test_ratings.clear();
    }
    ref_count++;
  } else {
    assert(ref_count > 0);
    ref_count--;
  }
  _town_rating_test = !(ref_count == 0);
}
void SetTownRatingTestMode(bool mode) {…}
 
static int GetRating(const Town *t)
{
  if (_town_rating_test) {
    auto it = _town_test_ratings.find(t);
    if (it != _town_test_ratings.end()) {
      return it->second;
    }
  }
  return t->ratings[_current_company];
}
static int GetRating(const Town *t) {…}
 
void ChangeTownRating(Town *t, int add, int max, DoCommandFlags flags)
{
  /* if magic_bulldozer cheat is active, town doesn't penalize for removing stuff */
  if (t == nullptr || flags.Test(DoCommandFlag::NoModifyTownRating) ||
      !Company::IsValidID(_current_company) ||
      (_cheats.magic_bulldozer.value && add < 0)) {
    return;
  }
 
  int rating = GetRating(t);
  if (add < 0) {
    if (rating > max) {
      rating += add;
      if (rating < max) rating = max;
    }
  } else {
    if (rating < max) {
      rating += add;
      if (rating > max) rating = max;
    }
  }
  if (_town_rating_test) {
    _town_test_ratings[t] = rating;
  } else {
    t->have_ratings.Set(_current_company);
    t->ratings[_current_company] = rating;
    SetWindowDirty(WC_TOWN_AUTHORITY, t->index);
  }
}
void ChangeTownRating(Town *t, int add, int max, DoCommandFlags flags) {…}
 
CommandCost CheckforTownRating(DoCommandFlags flags, Town *t, TownRatingCheckType type)
{
  /* if magic_bulldozer cheat is active, town doesn't restrict your destructive actions */
  if (t == nullptr || !Company::IsValidID(_current_company) ||
      _cheats.magic_bulldozer.value || flags.Test(DoCommandFlag::NoTestTownRating)) {
    return CommandCost();
  }
 
  /* minimum rating needed to be allowed to remove stuff */
  static const int needed_rating[][TOWN_RATING_CHECK_TYPE_COUNT] = {
    /*                  ROAD_REMOVE,                    TUNNELBRIDGE_REMOVE */
    {    RATING_ROAD_NEEDED_LENIENT,    RATING_TUNNEL_BRIDGE_NEEDED_LENIENT}, // Lenient
    {    RATING_ROAD_NEEDED_NEUTRAL,    RATING_TUNNEL_BRIDGE_NEEDED_NEUTRAL}, // Neutral
    {    RATING_ROAD_NEEDED_HOSTILE,    RATING_TUNNEL_BRIDGE_NEEDED_HOSTILE}, // Hostile
    { RATING_ROAD_NEEDED_PERMISSIVE, RATING_TUNNEL_BRIDGE_NEEDED_PERMISSIVE}, // Permissive
  };
 
  /* check if you're allowed to remove the road/bridge/tunnel
   * owned by a town no removal if rating is lower than ... depends now on
   * difficulty setting. Minimum town rating selected by difficulty level
   */
  int needed = needed_rating[_settings_game.difficulty.town_council_tolerance][type];
 
  if (GetRating(t) < needed) {
    return CommandCostWithParam(STR_ERROR_LOCAL_AUTHORITY_REFUSES_TO_ALLOW_THIS, t->index);
  }
 
  return CommandCost();
}
CommandCost CheckforTownRating(DoCommandFlags flags, Town *t, TownRatingCheckType type) {…}
 
template <>
Town::SuppliedHistory SumHistory(std::span<const Town::SuppliedHistory> history)
{
  uint32_t production = std::accumulate(std::begin(history), std::end(history), 0, [](uint32_t r, const auto &s) { return r + s.production; });
  uint32_t transported = std::accumulate(std::begin(history), std::end(history), 0, [](uint32_t r, const auto &s) { return r + s.transported; });
  auto count = std::size(history);
  return {.production = ClampTo<uint16_t>(production / count), .transported = ClampTo<uint16_t>(transported / count)};
}
 
static const IntervalTimer<TimerGameEconomy> _economy_towns_monthly({TimerGameEconomy::MONTH, TimerGameEconomy::Priority::TOWN}, [](auto)
{
  for (Town *t : Town::Iterate()) {
    /* Check for active town actions and decrement their counters. */
    if (t->road_build_months != 0) t->road_build_months--;
    if (t->fund_buildings_months != 0) t->fund_buildings_months--;
 
    if (t->exclusive_counter != 0) {
      if (--t->exclusive_counter == 0) t->exclusivity = CompanyID::Invalid();
    }
 
    /* Check for active failed bribe cooloff periods and decrement them. */
    for (const Company *c : Company::Iterate()) {
      if (t->unwanted[c->index] > 0) t->unwanted[c->index]--;
    }
 
    UpdateValidHistory(t->valid_history, HISTORY_YEAR, TimerGameEconomy::month);
 
    /* Update cargo statistics. */
    for (auto &s : t->supplied) RotateHistory(s.history, t->valid_history, HISTORY_YEAR, TimerGameEconomy::month);
    for (auto &received : t->received) received.NewMonth();
 
    UpdateTownGrowth(t);
    UpdateTownRating(t);
 
    SetWindowDirty(WC_TOWN_VIEW, t->index);
  }
});
 
static const IntervalTimer<TimerGameEconomy> _economy_towns_yearly({TimerGameEconomy::YEAR, TimerGameEconomy::Priority::TOWN}, [](auto)
{
  /* Increment house ages */
  for (const auto t : Map::Iterate()) {
    if (!IsTileType(t, MP_HOUSE)) continue;
    IncrementHouseAge(t);
  }
});
 
static CommandCost TerraformTile_Town(TileIndex tile, DoCommandFlags flags, int z_new, Slope tileh_new)
{
  if (AutoslopeEnabled()) {
    HouseID house = GetHouseType(tile);
    GetHouseNorthPart(house); // modifies house to the ID of the north tile
    const HouseSpec *hs = HouseSpec::Get(house);
 
    /* Here we differ from TTDP by checking BuildingFlag::NotSloped */
    if (!hs->building_flags.Test(BuildingFlag::NotSloped) && !IsSteepSlope(tileh_new) &&
        (GetTileMaxZ(tile) == z_new + GetSlopeMaxZ(tileh_new))) {
      bool allow_terraform = true;
 
      /* Call the autosloping callback per tile, not for the whole building at once. */
      house = GetHouseType(tile);
      hs = HouseSpec::Get(house);
      if (hs->callback_mask.Test(HouseCallbackMask::Autoslope)) {
        /* If the callback fails, allow autoslope. */
        uint16_t res = GetHouseCallback(CBID_HOUSE_AUTOSLOPE, 0, 0, house, Town::GetByTile(tile), tile);
        if (res != CALLBACK_FAILED && ConvertBooleanCallback(hs->grf_prop.grffile, CBID_HOUSE_AUTOSLOPE, res)) allow_terraform = false;
      }
 
      if (allow_terraform) return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
    }
  }
 
  return Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile);
}
 
extern const TileTypeProcs _tile_type_town_procs = {
  DrawTile_Town,           // draw_tile_proc
  GetSlopePixelZ_Town,     // get_slope_z_proc
  ClearTile_Town,          // clear_tile_proc
  AddAcceptedCargo_Town,   // add_accepted_cargo_proc
  GetTileDesc_Town,        // get_tile_desc_proc
  GetTileTrackStatus_Town, // get_tile_track_status_proc
  nullptr,                    // click_tile_proc
  AnimateTile_Town,        // animate_tile_proc
  TileLoop_Town,           // tile_loop_proc
  ChangeTileOwner_Town,    // change_tile_owner_proc
  AddProducedCargo_Town,   // add_produced_cargo_proc
  nullptr,                    // vehicle_enter_tile_proc
  GetFoundation_Town,      // get_foundation_proc
  TerraformTile_Town,      // terraform_tile_proc
};
 
std::span<const DrawBuildingsTileStruct> GetTownDrawTileData()
{
  return _town_draw_tile_data;
}