Function LoadTownData

src/genworld.cpp:359–510

* Load town data from _file_to_saveload, place towns at the appropriate locations, and expand them to their target populations. */

 * Load town data from _file_to_saveload, place towns at the appropriate locations, and expand them to their target populations.
 */
void LoadTownData()
{
	/* Load the JSON file as a string initially. We'll parse it soon. */
	size_t filesize;
	auto f = FioFOpenFile(_file_to_saveload.name, "rb", HEIGHTMAP_DIR, &filesize);

	if (!f.has_value()) {
		ShowErrorMessage(GetEncodedString(STR_TOWN_DATA_ERROR_LOAD_FAILED),
			GetEncodedString(STR_TOWN_DATA_ERROR_JSON_FORMATTED_INCORRECTLY), WL_ERROR);
		return;
	}

	std::string text(filesize, '\0');
	size_t len = fread(text.data(), filesize, 1, *f);
	f.reset();
	if (len != 1) {
		ShowErrorMessage(GetEncodedString(STR_TOWN_DATA_ERROR_LOAD_FAILED),
			GetEncodedString(STR_TOWN_DATA_ERROR_JSON_FORMATTED_INCORRECTLY), WL_ERROR);
		return;
	}

	/* Now parse the JSON. */
	nlohmann::json town_data;
	try {
		town_data = nlohmann::json::parse(text);
	} catch (nlohmann::json::exception &) {
		ShowErrorMessage(GetEncodedString(STR_TOWN_DATA_ERROR_LOAD_FAILED), GetEncodedString(STR_TOWN_DATA_ERROR_JSON_FORMATTED_INCORRECTLY), WL_ERROR);
		return;
	}

	/* Check for JSON formatting errors with the array of towns. */
	if (!town_data.is_array()) {
		ShowErrorMessage(GetEncodedString(STR_TOWN_DATA_ERROR_LOAD_FAILED), GetEncodedString(STR_TOWN_DATA_ERROR_JSON_FORMATTED_INCORRECTLY), WL_ERROR);
		return;
	}

	std::vector<std::pair<Town *, uint> > towns;
	uint failed_towns = 0;

	/* Iterate through towns and attempt to found them. */
	for (auto &feature : town_data) {
		std::string name; // The name of the town.
		uint population; // The target population of the town when created in OpenTTD. If input is blank, defaults to 0.
		bool is_city; // Should it be created as a city in OpenTTD? If input is blank, defaults to false.
		float x_proportion; // The X coordinate of the town, as a proportion 0..1 of the maximum X coordinate.
		float y_proportion; // The Y coordinate of the town, as a proportion 0..1 of the maximum Y coordinate.

		/* Ensure JSON is formatted properly. */
		if (!feature.is_object()) {
			ShowErrorMessage(GetEncodedString(STR_TOWN_DATA_ERROR_LOAD_FAILED), GetEncodedString(STR_TOWN_DATA_ERROR_JSON_FORMATTED_INCORRECTLY), WL_ERROR);
			return;
		}

		/* Check to ensure all fields exist and are of the correct type.
		 * If the town name is formatted wrong, all we can do is give a general warning. */
		if (!feature.contains("name") || !feature.at("name").is_string()) {
			ShowErrorMessage(GetEncodedString(STR_TOWN_DATA_ERROR_LOAD_FAILED), GetEncodedString(STR_TOWN_DATA_ERROR_JSON_FORMATTED_INCORRECTLY), WL_ERROR);
			return;