aglSetWindowRef chopping

Hi All

There is a small but annoying problem: aglSetWindowRef clears viewport with background color (with second parameter NULL as well).
As a result window is redrawn “part by part”, irritating user.
I’ve tried

  • glViewPort, glScissor, CGCaptureDisplay, EnableScreenUpdates (all has no effect)

  • set AGL_BUFFER_RECT to empty (or just call aglDestroyContext without aglSetWindowRef) does same unwanted cleanup.

Any idea?