Function TerraformTileHeight

src/terraform_cmd.cpp:99–159

* Terraform the north corner of a tile to a specific height. * * @param ts TerraformerState. * @param tile Tile. * @param height Aimed height. * @return Error code or cost. */

 * @return Error code or cost.
 */
static std::tuple<CommandCost, TileIndex> TerraformTileHeight(TerraformerState *ts, TileIndex tile, int height)
{
	assert(tile < Map::Size());

	/* Check range of destination height */
	if (height < 0) return { CommandCost(STR_ERROR_ALREADY_AT_SEA_LEVEL), INVALID_TILE };
	if (height > _settings_game.construction.map_height_limit) return { CommandCost(STR_ERROR_TOO_HIGH), INVALID_TILE };

	/*
	 * Check if the terraforming has any effect.
	 * This can only be true, if multiple corners of the start-tile are terraformed (i.e. the terraforming is done by towns/industries etc.).
	 * In this case the terraforming should fail. (Don't know why.)
	 */
	if (height == TerraformGetHeightOfTile(ts, tile)) return { CMD_ERROR, INVALID_TILE };

	/* Check "too close to edge of map". Only possible when freeform-edges is off. */
	uint x = TileX(tile);
	uint y = TileY(tile);
	if (!_settings_game.construction.freeform_edges && ((x <= 1) || (y <= 1) || (x >= Map::MaxX() - 1) || (y >= Map::MaxY() - 1))) {
		/*
		 * Determine a sensible error tile
		 */
		if (x == 1) x = 0;
		if (y == 1) y = 0;
		return { CommandCost(STR_ERROR_TOO_CLOSE_TO_EDGE_OF_MAP), TileXY(x, y) };
	}

	/* Mark incident tiles that are involved in the terraforming. */
	TerraformAddDirtyTileAround(ts, tile);

	/* Store the height modification */
	TerraformSetHeightOfTile(ts, tile, height);

	CommandCost total_cost(EXPENSES_CONSTRUCTION);

	/* Increment cost */
	total_cost.AddCost(_price[PR_TERRAFORM]);

	/* Recurse to neighboured corners if height difference is larger than 1 */
	for (DiagDirection dir = DIAGDIR_BEGIN; dir < DIAGDIR_END; dir++) {
		TileIndex neighbour_tile = AddTileIndexDiffCWrap(tile, TileIndexDiffCByDiagDir(dir));

		/* Not using IsValidTile as we want to also change MP_VOID tiles, which IsValidTile excludes. */
		if (neighbour_tile == INVALID_TILE) continue;

		/* Get TileHeight of neighboured tile as of current terraform progress */
		int r = TerraformGetHeightOfTile(ts, neighbour_tile);
		int height_diff = height - r;

		/* Is the height difference to the neighboured corner greater than 1? */
		if (abs(height_diff) > 1) {
			/* Terraform the neighboured corner. The resulting height difference should be 1. */
			height_diff += (height_diff < 0 ? 1 : -1);
			auto [cost, err_tile] = TerraformTileHeight(ts, neighbour_tile, r + height_diff);
			if (cost.Failed()) return { cost, err_tile };
			total_cost.AddCost(cost.GetCost());
		}
	}