It appears that the QMdiSubWindow's 'Qt::WA_DeleteOnClose' attribute is not having any effect anymore when the application's style sheet was changed. This leaves us with dangling sub windows after the main windows were closed. In order to make sure these sub windows are closed anyways, the sub windows are now explicitly deleted in 'RiuMainWindowBase::removeViewerFromMdiArea'.

ApplicationCode/UserInterface/RiuMainWindowBase.cpp

@@ -293,6 +293,8 @@ void RiuMainWindowBase::removeViewerFromMdiArea( QMdiArea* mdiArea, QWidget* vie
     }
     mdiArea->removeSubWindow( subWindowBeingClosed );
 
+    delete subWindowBeingClosed;
+
     QList<QMdiSubWindow*> subWindowList = mdiArea->subWindowList( QMdiArea::ActivationHistoryOrder );
     if ( !subWindowList.empty() )
     {