very slow paint on mac retina

The attached program will show that painting is really slow, and this translates to an awful user experience for our customers when selecting and scrolling in our advanced custom interfaces.  If you right-click the app bundle "app.app" in macos Finder, click "Get Info", select "Open in Low Resolution", you will get good responsiveness with the ugly lowdpi.  The program has a macro to enable opengl to demonstrate an ideal experience, but our large codebase cannot just swap in opengl where qpainter is used due to other show stopper qt bugs (QTBUG-66717 QTBUG-67288).