Index: window_QT.cpp
===================================================================
--- window_QT.cpp	(revision 1)
+++ window_QT.cpp	(working copy)
@@ -56,6 +56,9 @@
 //that is also the number of pixel per grid
 
 static CvWinProperties* global_control_panel = NULL;
+
+static bool externalQAppExists = false; // whether there already exists an "outside" qApp 
+
 //end static and global
 
 
@@ -438,7 +441,13 @@
 	// check initialization status
 	if( !wasInitialized)
 	{
-		new QApplication(*c,v);
+		// check if another "parent" app has already
+		// created an app object...
+		if (!QApplication::instance()) {
+			new QApplication(*c,v);
+		} else {
+			externalQAppExists = true;
+		}
 
 		wasInitialized = 1;
 		qDebug()<<"init done";
@@ -705,7 +714,10 @@
 	{
 		delete guiMainThread;//delete global_control_panel too
 		guiMainThread = NULL;
-		qApp->quit();
+		// only quit if we created the QApp ourselves...
+		if (!externalQAppExists) {
+			qApp->quit();
+		}
 	}
 }
 
@@ -974,6 +986,9 @@
 
 	if (multiThreads)
 	{
+		// WARNING: this could even close windows from an external parent app
+		//#TODO check externalQAppExists and in case it does, close windows carefully,
+		//      i.e. apply the className-check from below...
 		qApp->closeAllWindows();
 	}else{