#3768 and #3903 Fix border issue by making OpenGL widget a child of the main window.

ApplicationCode/ProjectDataModel/Rim3dView.cpp

@@ -190,7 +190,7 @@ QWidget* Rim3dView::createViewWidget(QWidget* mainWindowParent)
     QGLFormat glFormat;
     glFormat.setDirectRendering(RiaApplication::instance()->useShaders());
 
-    m_viewer = new RiuViewer(glFormat, nullptr);
+    m_viewer = new RiuViewer(glFormat, mainWindowParent);
     m_viewer->setOwnerReservoirView(this);
 
     cvf::String xLabel;