Rework Scene3D to fix potential crash on shutdown

- Rework Scene3DRenderer/Scene3DItem to remove coupling and help
  simplify the flow
- Introduce a Scene3DManagerNode to manager lifetime of the
  Scene3DRenderer. Rely on the Scene3DManagerNode dtor to know
  to shutdown the Qt3D renderer in the proper thread.
- Try to handle the fact that destruction order between Item and SGNode
  is random by using an AspectEngineDestroyer helper
- Stop using a sharedptr to store the QEntity on the Scene3DItem side.
  This can lead to crashes as the AspectEngine assumes it is the sole
  owner of the Entity ptr.

Change-Id: I14915705eb9ab1195b2b783cbbb45076acc2ac1a
Task-number: QTBUG-84847
Reviewed-by: Mike Krus <mike.krus@kdab.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/src/plugins/renderers/opengl/renderer/renderer.cpp b/src/plugins/renderers/opengl/renderer/renderer.cpp
index 27e00d9cb..27c3a61ca 100644
--- a/src/plugins/renderers/opengl/renderer/renderer.cpp
+++ b/src/plugins/renderers/opengl/renderer/renderer.cpp
@@ -534,7 +534,11 @@ void Renderer::shutdown()
     QMutexLocker lock(&m_hasBeenInitializedMutex);
 
     qCDebug(Backend) << Q_FUNC_INFO << "Requesting renderer shutdown";
-    m_running.storeRelaxed(0);
+    const bool wasRunning = m_running.testAndSetRelaxed(1, 0);
+
+    // We might have already been shutdown
+    if (!wasRunning)
+        return;
 
     // We delete any renderqueue that we may not have had time to render
     // before the surface was destroyed
@@ -1780,7 +1784,7 @@ bool Renderer::shouldRender() const
 {
     // Only render if something changed during the last frame, or the last frame
     // was not rendered successfully (or render-on-demand is disabled)
-    return (m_settings->renderPolicy() == QRenderSettings::Always
+    return ((m_settings && m_settings->renderPolicy() == QRenderSettings::Always)
             || m_dirtyBits.marked != 0
             || m_dirtyBits.remaining != 0
             || !m_lastFrameCorrect.loadRelaxed());