Force single threaded OSG widget when with Qt5

src/gui/main.cc.in

@@ -40,7 +40,7 @@ int main(int argc, char *argv[])
 
   SafeApplication a(argc, argv);
   a.setStyle(QStyleFactory::create (
-#if USE_QT4
+#ifdef USE_QT4
         "cleanlooks"
 #else // USE_QT4
         "fusion"

src/gui/mainwindow.cc

@@ -216,7 +216,11 @@ namespace gepetto {
         delayedCreateView_.unlock();
         return osgWindows_.last();
       } else {
-        OSGWidget* osgWidget = new OSGWidget (osgViewerManagers_, name, this, 0);
+        OSGWidget* osgWidget = new OSGWidget (osgViewerManagers_, name, this, 0
+#ifndef USE_QT4
+            , osgViewer::Viewer::SingleThreaded
+#endif // USE_QT4
+            );
         osgWidget->setObjectName(name.c_str());
         addOSGWidget (osgWidget);
         emit viewCreated(osgWidget);