Allow the backend chance to process any final changes during shutdown

The QAspectEngine now flushes any pending changes batched up before
telling the aspect manager to exit the simulation loop.

Furthermore, the call to QAspectManager::exitSimulationLoop() now
waits until the aspect thread has completely finished the simulation
loop and has called onEngineShutdown() on each of the aspects. This is
important to ensure that the main thread doesn't call
QAspectEngine::shutdown() too early as this deletes the change queue
which contains the final changes sent from the main thread during
shutdown.

For some reason the backend is unable to find which
QBackendNodeMapper corresponds to each destruction change. Will
investigate that next.

Task-number: QTBUG-42353
Change-Id: Iec4d6a57a163effefd5b60249bf97c76ed187413
Reviewed-by: Kevin Ottens <kevin.ottens@kdab.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/core/aspects/qaspectmanager_p.h b/src/core/aspects/qaspectmanager_p.h
index 5be415533..7f941b2bf 100644
--- a/src/core/aspects/qaspectmanager_p.h
+++ b/src/core/aspects/qaspectmanager_p.h
@@ -112,6 +112,7 @@ private:
     QAtomicInt m_runSimulationLoop;
     QAtomicInt m_runMainLoop;
     QScopedPointer<QServiceLocator> m_serviceLocator;
+    QSemaphore m_waitForEndOfSimulationLoop;
     QSemaphore m_waitForEndOfExecLoop;
     QSemaphore m_waitForQuit;
 };