QGraphicsEffect doesn't seem to work for QOpenGLWidget

Specifying a graphics effect to a QOpenGLWidget using setGraphicsEffect(QGraphicsEffect *) does not seem to have any effect.

The same code using a QWidget instead of a QOpenGLWidget does render the graphics effect as expected.

It would be nice if I could use graphics effects with QOpenGLWidget in the same way that I use them with QWidget. If that is impractical, I suggest adding a note to the QOpenGLWidget or setGraphicsEffect(QGraphicsEffect *) documentation to point out that limitation.