Added some classes from a stackoverflow to utilize Qt's concurrency functions especially cancellable QFuture's

core/ControllableTask.h

@@ -0,0 +1,18 @@
+#ifndef CONTROLLABLETASK_H
+#define CONTROLLABLETASK_H
+/** From answer by Hatter
+ *
+ * https://stackoverflow.com/questions/5423058/qfuture-that-can-be-cancelled-and-report-progress
+ */
+
+#include "TaskControl.h"
+
+template <class T>
+class ControllableTask
+{
+public:
+	virtual ~ControllableTask() {}
+	virtual T run(TaskControl& control) = 0;
+};
+
+#endif // CONTROLLABLETASK_H

core/RunControllableTask.h

@@ -0,0 +1,45 @@
+#ifndef RUNCONTROLLABLETASK_H
+#define RUNCONTROLLABLETASK_H
+/** From answer by Hatter
+ *
+ * https://stackoverflow.com/questions/5423058/qfuture-that-can-be-cancelled-and-report-progress
+ */
+
+#include <QFutureInterface>
+#include <QRunnable>
+#include "ControllableTask.h"
+
+template <typename T>
+class RunControllableTask : public QFutureInterface<T> , public QRunnable
+{
+public:
+	RunControllableTask(ControllableTask<T>* tsk) : task(tsk) { }
+	virtial ~RunControllableTask() { delete task; }
+
+	QFuture<T> start()
+	{
+		this->setRunnable(this);
+		this->reportStarted();
+		QFuture<T> future = this->future();
+		QThreadPool::globalInstance()->start(this, /*m_priority*/ 0);
+		return future;
+	}
+
+	void run()
+	{
+		if (this->isCanceled()) {
+			this->reportFinished();
+			return;
+		}
+		TaskControl control(this);
+		result = this->task->run(control);
+		if (!this->isCanceled()) {
+			this->reportResult(result);
+		}
+		this->reportFinished();
+	}
+
+	T  result;
+	ControllableTask<T> *task;
+};
+#endif // RUNCONTROLLABLETASK_H

core/TaskControl.h

@@ -0,0 +1,19 @@
+#ifndef TASKCONTROL_H
+#define TASKCONTROL_H
+/** From answer by Hatter
+ *
+ * https://stackoverflow.com/questions/5423058/qfuture-that-can-be-cancelled-and-report-progress
+ */
+
+#include <QFutureInterfaceBase>
+
+class TaskControl
+{
+public:
+	TaskControl(QFutureInterfaceBase *f) : fu(f) {  }
+	bool shouldRun() const { return !fu->isCanceled(); }
+private:
+	QFutureInterfaceBase *fu;
+};
+
+#endif // TASKCONTROL_H

core/TaskExecutor.h

@@ -0,0 +1,32 @@
+#ifndef TASKEXECUTOR_H
+#define TASKEXECUTOR_H
+/* From answer by Hatter
+ *
+ * https://stackoverflow.com/questions/5423058/qfuture-that-can-be-cancelled-and-report-progress
+ */
+#include "ControllableTask.h"
+#include "RunControllableTask.h"
+
+/**
+ * @brief The TaskExecutor class
+ *
+ * The user should sublass ControllableTask, implement background routine which checks sometimes
+ * method shouldRun() of TaskControl instance passed to run(TaskControl&) and then use it like:
+ *
+ * QFututre<int> futureValue = TaskExecutor::run(new SomeControllableTask(inputForThatTask));
+ *
+ * Then she may cancel it by calling futureValue.cancel(), bearing in mind that cancellation is
+ * graceful and not immediate.
+ *
+ */
+class TaskExecutor {
+public:
+	template <class T>
+	static QFuture<T> run(ControllableTask<T>* task) {
+		return (new RunControllableTask<T>(task))->start();
+	}
+};
+
+
+
+#endif // TASKEXECUTOR_H

core/core.pro

@@ -50,7 +50,11 @@ HEADERS += PasswordManager.h \
 	Expected.h \
     ExplainTreeModelItem.h \
     json/json.h \
-    WorkManager.h
+    WorkManager.h \
+    TaskControl.h \
+    ControllableTask.h \
+    RunControllableTask.h \
+    TaskExecutor.h
 	
 unix {
     target.path = /usr/lib