The MainWindow now uses a background task to load the catalog.

As the background task can't be cancelled yet only closing of the window
can block if the task is still running.

core/QueuedBackgroundTask.cpp

@@ -1,4 +1,64 @@
 #include "QueuedBackgroundTask.h"
+#include "ScopeGuard.h"
 
-void QueuedBackgroundTask::requestPause()
-{}
+//void QueuedBackgroundTask::requestPause()
+//{}
+
+QueuedBackgroundTask::QueuedBackgroundTask(CompletionFunction on_completion)
+	: m_completionFunction(on_completion)
+{
+	setAutoDelete(false);
+}
+
+QueuedBackgroundTask::~QueuedBackgroundTask()
+{
+	cancel();
+	wait();
+}
+
+void QueuedBackgroundTask::cancel()
+{
+	QMutexLocker lock(&stateMutex);
+	if (!m_finished)
+		m_canceled = true;
+}
+
+void QueuedBackgroundTask::wait()
+{
+	QMutexLocker lock(&stateMutex);
+	if (!m_finished)
+		finished.wait(&stateMutex);
+}
+
+bool QueuedBackgroundTask::hasException() const
+{
+	return doRunException != nullptr;
+}
+
+void QueuedBackgroundTask::rethrow()
+{
+	std::rethrow_exception(doRunException);
+}
+
+void QueuedBackgroundTask::run()
+{
+	SCOPE_EXIT {
+		m_finished = true;
+		QMutexLocker lock(&stateMutex);
+		finished.notify_all();
+	};
+	QMutexLocker lock(&stateMutex);
+	m_started = true;
+	if (!m_canceled) {
+		lock.unlock();
+		try {
+			doRun();
+		}
+		catch (...) {
+			doRunException = std::current_exception();
+		}
+
+		if (!m_canceled && m_completionFunction)
+			m_completionFunction(this);
+	}
+}