Merge topic 'revert-offscreen-rendering-commit'

52780a73 Revert "Better handle off-screen renders in QVTKOpenGLWidget."

Acked-by: Kitware Robot <kwrobot@kitware.com>
Reviewed-by: Utkarsh Ayachit <utkarsh.ayachit@kitware.com>
Merge-request: !2648