Function ensureProjCacheDirectory

src/core/georeferencing.cpp:106–143

* Maintains and returns the cache directory for PROJ resource files. * * PROJ resources may change with different versions of Mapper. * This function creates the directory if it is missing, * but also resets it on Mapper version changes. */

	 * but also resets it on Mapper version changes.
	 */
	QDir ensureProjCacheDirectory()
	{
		auto cache = QDir(QStandardPaths::writableLocation(QStandardPaths::CacheLocation));
		auto const proj = QStringLiteral("proj");
		auto const version_filename = QStringLiteral("proj/org.openorienteering.mapper");
		if (cache.exists(proj))
		{
			QFile version_file(cache.filePath(version_filename));
			if (!version_file.open(QIODevice::ReadOnly)
			    || version_file.readAll() != APP_VERSION)
			{
				qDebug("PROJ cache version mismatch");
				auto proj_dir = cache;
				if (!proj_dir.cd(proj) || !proj_dir.removeRecursively())
					qDebug("Failed to remove PROJ cache");
			}
		}
		if (!cache.exists(proj))
		{
			qDebug("Creating PROJ cache, version '" APP_VERSION "'");
			if (cache.mkpath(proj))
			{
				QFile version_file(cache.filePath(version_filename));
				if (!version_file.open(QIODevice::WriteOnly)
				    || version_file.write(APP_VERSION) != qstrlen(APP_VERSION))
				{
					qDebug("Failed to write PROJ cache version file");
				}
			}
			else
			{
				qDebug("Could not create a PROJ cache");
			}
		}
		
		cache.cd(proj);
		return cache;
	}
	
	/**
	 * Provides a cache directory for RROJ resource files.