Function TryBuildTownHouse

src/town_cmd.cpp:2814–2936

* Tries to build a house at this tile. * @param t The town the house will belong to. * @param tile The tile to try building on. * @return false iff no house can be built on this tile. */

 * @return false iff no house can be built on this tile.
 */
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;