Makes a firmer attempt at enforcing safe shutdown.

OSBindings/Qt/functionthread.h

@@ -1,36 +1,81 @@
 #ifndef FUNCTIONTHREAD_H
 #define FUNCTIONTHREAD_H
 
+#include <atomic>
+#include <QApplication>
+#include <QDebug>
+#include <QEvent>
 #include <QThread>
 
 /*!
  * \brief The LambdaThread class
  *
- * Provides a QThread which performs a supplied lambda before kicking off its event loop.
+ * Provides a QThread to which lambdas can be posted.
  *
  * Disclaimer: this might be a crutch that reveals a misunderstanding of the Qt
  * threading infrastructure. We'll see.
  */
 class FunctionThread: public QThread {
 	public:
-		FunctionThread() : QThread() {}
-
-		void setFunction(const std::function<void(void)> &function) {
-			this->function = function;
+		FunctionThread() : QThread() {
+			// TODO: I've assumed a race condition here with the creation of performer; if QThread
+			// blocks on completion of `run` when starting then this is redundant.
+			performerFlag = false;
+			start();
+			while(!performerFlag);
 		}
 
 		void run() override {
-			function();
+			// Gymnastics here: events posted directly to the QThread will occur on the thread
+			// that created the QThread. To have events occur within a QThread, they have to be
+			// posted to an object created on that thread. FunctionPerformer fills that role.
+			performer = std::make_unique<FunctionPerformer>();
+			performerFlag = true;
 			exec();
 		}
 
 		void stop() {
-			quit();
+			performAsync([this] {
+				this->quit();
+			});
 			wait();
 		}
 
+		/*!
+		 * \brief Schedules a function to be performed on this thread. Control
+		 * must return to the main event loop for the function to be performed;
+		 * use QCoreApplication::sendPostedEvents() to ensure the function is
+		 * performed before then, if required.
+		 *
+		 * \param function The function to perform.
+		 */
+		void performAsync(const std::function<void(void)> &function) {
+			QApplication::instance()->postEvent(performer.get(), new FunctionEvent(function));
+			QCoreApplication::sendPostedEvents();
+		}
+
 	private:
-		std::function<void(void)> function;
+		struct FunctionEvent: public QEvent {
+			FunctionEvent(const std::function<void(void)> &function) : QEvent(QEvent::Type::User), function(function) {}
+			std::function<void(void)> function;
+		};
+
+		struct FunctionPerformer: public QObject {
+			FunctionPerformer(): QObject() {}
+
+			bool event(QEvent *event) override {
+				if(event->type() == QEvent::Type::User) {
+					const auto functionEvent = dynamic_cast<FunctionEvent *>(event);
+					if(functionEvent) {
+						functionEvent->function();
+						return true;
+					}
+				}
+				return QObject::event(event);
+			}
+		};
+		std::unique_ptr<FunctionPerformer> performer;
+		std::atomic<bool> performerFlag;
 };
 
 #endif // FUNCTIONTHREAD_H

OSBindings/Qt/mainwindow.cpp

@@ -65,7 +65,9 @@ void MainWindow::open() {
 MainWindow::~MainWindow() {
 	// Stop the audio output, and its thread.
 	if(audioOutput) {
-//		QMetaObject::invokeMethod(audioOutput.get(), "stop", Qt::BlockingQueuedConnection);
+		audioThread.performAsync([this] {
+			audioOutput->stop();
+		});
 		audioThread.stop();
 	}
 
@@ -164,7 +166,7 @@ void MainWindow::launchMachine() {
 					speaker->set_output_rate(idealFormat.sampleRate(), samplesPerBuffer, audioIsStereo);
 					speaker->set_delegate(this);
 
-					audioThread.setFunction([this, idealFormat] {
+					audioThread.performAsync([this, idealFormat] {
 						// Create an audio output.
 						audioOutput = std::make_unique<QAudioOutput>(idealFormat);
 
@@ -174,7 +176,6 @@ void MainWindow::launchMachine() {
 						audioOutput->start(&audioBuffer);
 						audioBuffer.setDepth(audioOutput->bufferSize());
 					});
-					audioThread.start();
 				}
 			}
 

OSBindings/Qt/timer.cpp

@@ -5,8 +5,13 @@
 #include <algorithm>
 #include <QDebug>
 
-Timer::Timer(QObject *parent) : QObject(parent) {
-	thread.setFunction([this] {
+Timer::Timer(QObject *parent) : QObject(parent) {}
+
+void Timer::startWithMachine(MachineTypes::TimedMachine *machine, std::mutex *machineMutex) {
+	this->machine = machine;
+	this->machineMutex = machineMutex;
+
+	thread.performAsync([this] {
 		// Set up the emulation timer. Bluffer's guide: the QTimer will post an
 		// event to an event loop. QThread is a thread with an event loop.
 		// My class, Timer, will be wired up to receive the QTimer's events.
@@ -18,13 +23,6 @@ Timer::Timer(QObject *parent) : QObject(parent) {
 	});
 }
 
-void Timer::startWithMachine(MachineTypes::TimedMachine *machine, std::mutex *machineMutex) {
-	this->machine = machine;
-	this->machineMutex = machineMutex;
-
-	thread.start();
-}
-
 void Timer::tick() {
 	const auto now = Time::nanos_now();
 	const auto duration = std::min(now - lastTickNanos, int64_t(500'000'000));
@@ -35,6 +33,8 @@ void Timer::tick() {
 }
 
 Timer::~Timer() {
-	QMetaObject::invokeMethod(timer.get(), "stop", Qt::BlockingQueuedConnection);
+	thread.performAsync([this] {
+		timer->stop();
+	});
 	thread.stop();
 }