stereo in Qt using Open GL

I am trying to make a stereo window in Qt. I seem to be lost in the interaction of Qt and OpenGL.

I have set the stereo context in my GL initialization co开发者_Python百科de

QGLFormat fmt
fmt.setStereo(true)

and when I check the value, it comes back true.

I then draw into the GL_BACK_LEFT and GL_BACK_RIGHT buffers (I have also tried just GL_LEFT and GL_RIGHT) but the resultant scene contains both sets of polygons.

I know that my hardware (NVIDIA Quadro FX 3500) supports stereo in a window, since other applications (for which I do not have source code) work fine.

Does this symptom seem familiar to anybody, enough so that it might be obvious what stupid mistake I am making?

Windows XP, Qt 4.4.2, MS Studio 2005

It never fails.
Ask a question, and figure out the answer within minutes of asking for help. Oh well, hopefully somebody else might benefit.

I was doing this

fmt.setStereo(true)

but not this

setFormat(fmt);

now it seems to work more like I want to to.