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.h

@@ -1,52 +1,81 @@
-#pragma once 
+#pragma once 
 
+#include <functional>
 #include <QRunnable>
-#include <QVector>
+//#include <QVector>
+#include <QMutex>
+#include <QWaitCondition>
 
 /** Base class for an object that can be queued for execution in the background.
  * 
- * It is meaned for long running processes the end user might want to abort, pause and check progress on.
+ * It is meaned for long running processes the end user might want to abort,
+ * pause and check progress on.
  */
-class QueuedBackgroundTask: public QRunnable
-{
-    /** Task should exit it's run method but remember it's state, it might be resumed later.
-     */
-    void requestPause();
-    
-    /** Request to stop running and forget progress
-     */
-    void requestAbort();
-    
-    QString getProgressInfo();
-};
-
-class BackgroundTaskInfo {
-public:   
-};
-
-/** Manages objects of type QueuedBackgroundTask
- * 
- * The basic operation of this queue is hand everything directly of to the default
- * threadpool and that will decide when to run each task. But extra functions are 
- * provided to control tasks to allow the program to have a UI for controlling the tasks
- */
-class BackgroundTaskQueue {
-    
+class QueuedBackgroundTask: public QRunnable {
 public:
+	using CompletionFunction = std::function<void(QRunnable *)>;
+
+	explicit QueuedBackgroundTask(CompletionFunction on_completion);
+	virtual ~QueuedBackgroundTask();
+
+	void cancel();
+	void wait();
+	bool hasException() const;
+	void rethrow();
+
+protected:
+
+	bool m_canceled = false;
+	bool m_started = false;
+	bool m_finished = false;
+	std::exception_ptr doRunException = nullptr;
+	CompletionFunction m_completionFunction = nullptr;
+
+	QMutex stateMutex;
+	QWaitCondition finished;
+
+	virtual void run() override;
+
+	virtual void doRun() = 0;
+
+//    /** Task should exit it's run method but remember it's state, it might be resumed later.
+//     */
+//    void requestPause();
     
-    /** Returns a list of tasks in the queue and their progress.
-     * 
-     * When building a UI to show realtime activity then make sure to first register the update events
-     * then get the snapshot. After that you can use the events to update the contents of the UI.
-     */
-    QVector<BackgroundTaskInfo> getTaskInfoSnapshort();
-    
-    void pauseTask( );
-    
-    /** Resume a paused task
-     */
-    void resumeTask( );
-    
-    void abortTask( );
+//    /** Request to stop running and forget progress
+//     */
+//    void requestAbort();
     
+//    QString getProgressInfo();
 };
+
+//class BackgroundTaskInfo {
+//public:
+//};
+
+///** Manages objects of type QueuedBackgroundTask
+// *
+// * The basic operation of this queue is hand everything directly of to the default
+// * threadpool and that will decide when to run each task. But extra functions are
+// * provided to control tasks to allow the program to have a UI for controlling the tasks
+// */
+//class BackgroundTaskQueue {
+    
+//public:
+    
+//    /** Returns a list of tasks in the queue and their progress.
+//     *
+//     * When building a UI to show realtime activity then make sure to first register the update events
+//     * then get the snapshot. After that you can use the events to update the contents of the UI.
+//     */
+//    QVector<BackgroundTaskInfo> getTaskInfoSnapshort();
+    
+//    void pauseTask( );
+    
+//    /** Resume a paused task
+//     */
+//    void resumeTask( );
+    
+//    void abortTask( );
+    
+//};