Fix timer managmement during shutdown

interface/src/Application.cpp

@@ -1759,10 +1759,12 @@ Application::Application(int& argc, char** argv, QElapsedTimer& startupTimer, bo
 
     // Make sure we don't time out during slow operations at startup
     updateHeartbeat();
-
     QTimer* settingsTimer = new QTimer();
     moveToNewNamedThread(settingsTimer, "Settings Thread", [this, settingsTimer]{
-        connect(qApp, &Application::beforeAboutToQuit, [this, settingsTimer]{
+        // This needs to run on the settings thread, so we need to pass the `settingsTimer` as the 
+        // receiver object, otherwise it will run on the application thread and trigger a warning
+        // about trying to kill the timer on the main thread.
+        connect(qApp, &Application::beforeAboutToQuit, settingsTimer, [this, settingsTimer]{
             // Disconnect the signal from the save settings
             QObject::disconnect(settingsTimer, &QTimer::timeout, this, &Application::saveSettings);
             // Stop the settings timer

libraries/audio-client/src/AudioClient.cpp

@@ -101,6 +101,13 @@ QList<QAudioDeviceInfo> getAvailableDevices(QAudio::Mode mode) {
 
 // now called from a background thread, to keep blocking operations off the audio thread
 void AudioClient::checkDevices() {
+    // Make sure we're not shutting down
+    Lock timerMutex(_checkDevicesMutex);
+    // If we HAVE shut down after we were queued, but prior to execution, early exit
+    if (nullptr == _checkDevicesTimer) {
+        return;
+    }
+
     auto inputDevices = getAvailableDevices(QAudio::AudioInput);
     auto outputDevices = getAvailableDevices(QAudio::AudioOutput);
 
@@ -278,8 +285,8 @@ void AudioClient::customDeleter() {
     _shouldRestartInputSetup = false;
 #endif
     stop();
-    _checkDevicesTimer->stop();
-    _checkPeakValuesTimer->stop();
+    //_checkDevicesTimer->stop();
+    //_checkPeakValuesTimer->stop();
 
     deleteLater();
 }
@@ -648,12 +655,26 @@ void AudioClient::start() {
 }
 
 void AudioClient::stop() {
-
     qCDebug(audioclient) << "AudioClient::stop(), requesting switchInputToAudioDevice() to shut down";
     switchInputToAudioDevice(QAudioDeviceInfo(), true);
 
     qCDebug(audioclient) << "AudioClient::stop(), requesting switchOutputToAudioDevice() to shut down";
     switchOutputToAudioDevice(QAudioDeviceInfo(), true);
+
+    // Stop triggering the checks
+    QObject::disconnect(_checkPeakValuesTimer, &QTimer::timeout, nullptr, nullptr);
+    QObject::disconnect(_checkDevicesTimer, &QTimer::timeout, nullptr, nullptr);
+
+    // Destruction of the pointers will occur when the parent object (this) is destroyed)
+    {
+        Lock lock(_checkDevicesMutex);
+        _checkDevicesTimer = nullptr;
+    }
+    {
+        Lock lock(_checkPeakValuesMutex);
+        _checkPeakValuesTimer = nullptr;
+    }
+
 #if defined(Q_OS_ANDROID)
     _checkInputTimer.stop();
     disconnect(&_checkInputTimer, &QTimer::timeout, 0, 0);

libraries/audio-client/src/AudioClient.h

@@ -432,7 +432,9 @@ private:
     bool _shouldRestartInputSetup { true }; // Should we restart the input device because of an unintended stop?
 #endif
     
+    Mutex _checkDevicesMutex;
     QTimer* _checkDevicesTimer { nullptr };
+    Mutex _checkPeakValuesMutex;
     QTimer* _checkPeakValuesTimer { nullptr };
 
     bool _isRecording { false };

libraries/audio-client/src/AudioPeakValues.cpp

@@ -40,6 +40,12 @@ void release(IAudioClient* audioClient) {
 }
 
 void AudioClient::checkPeakValues() {
+    // Guard against running during shutdown
+    Lock timerMutex(_checkPeakValuesMutex);
+    if (nullptr == _checkPeakValuesTimer) {
+        return;
+    }
+
     // prepare the windows environment
     CoInitialize(NULL);