Hi David. I rebuilt Qt5 with the “-opengl desktop” option, but as far as I can tell the result is identical to what I built before.
I then tried making the changes you suggested to GUISupport/Qt/MakeLists.txt. I now get the same errors in compiling QVTKOpenGLNativeWidget.cxx.
I am starting to wonder if it is in fact possible to build VTK with Qt5.
Thanks again for your suggestions.