started qt6 migration

src/OpenMesh/Apps/Subdivider/qtsubdivider.cc

@@ -51,13 +51,20 @@
 #include <QApplication>
 #include <QMessageBox>
 #include "SubdivideWidget.hh"
+#if QT_VERSION_MAJOR > 5
+#include <QOpenGLContext>
+#endif
 
 int main(int argc, char **argv)
 {
   // OpenGL check
   QApplication app(argc,argv);
 
+#if QT_VERSION_MAJOR < 6
   if ( !QGLFormat::hasOpenGL() ) {
+#else
+  if ( QOpenGLContext::openGLModuleType() != QOpenGLContext::LibGL ) {
+#endif
     QString msg = "System has no OpenGL support!";
     QMessageBox::critical( nullptr, "OpenGL", msg + argv[1], QMessageBox::Ok );
     return -1;