ok, the culprit is
glRasterPos2i(0, 0);
in
void vtkOpenGLFreeTypeTextMapper::RenderOverlay(vtkViewport* viewport,
vtkActor2D* actor)
but failed tests are a result of updating my NVIDIA driver as of last week.
Any advice on how to proceed in a case such as this, other than
reverting back to my old NVIDIA driver?
Dean