Function IsConversionNeeded

src/settings.cpp:1347–1369

* Check whether a conversion should be done, and based on what old setting information. * * To prevent errors when switching back and forth between older and newer * version of OpenTTD, the type of a setting is never changed. Instead, the * setting is renamed, and this function is used to check whether a conversion * between the old and new setting is required. * * This checks if the new se

 * @return Whether upgrading should happen; if false, old_item is a nullptr.
 */
bool IsConversionNeeded(const ConfigIniFile &ini, const std::string &group, const std::string &old_var, const std::string &new_var, const IniItem **old_item)
{
	*old_item = nullptr;

	const IniGroup *igroup = ini.GetGroup(group);
	/* If the group doesn't exist, there is nothing to convert. */
	if (igroup == nullptr) return false;

	const IniItem *tmp_old_item = igroup->GetItem(old_var);
	const IniItem *new_item = igroup->GetItem(new_var);

	/* If the old item doesn't exist, there is nothing to convert. */
	if (tmp_old_item == nullptr) return false;

	/* If the new item exists, it means conversion was already done. We only
	 * do the conversion the first time, and after that these settings are
	 * independent. This allows users to freely change between older and
	 * newer clients without breaking anything. */
	if (new_item != nullptr) return false;

	*old_item = tmp_old_item;
	return true;
}

/**
 * Load the values from the configuration files