Starting with GL 3.0 it's legal to have no drawable bound to the current
context. GLX_SGI_video_sync doesn't take a drawable for an argument so
it implicitly operates on... something. NVIDIA's driver throws
GLX_BAD_CONTEXT for GetVideoSync, but WaitVideoSync seems to actually
wait for the next MSC on the context's screen. We could work around this
by internally creating/destroying a GLXWindow for the root window, but
for Xwayland there's not necessarily a good answer it can return.
Just throw GLX_BAD_CONTEXT for both.
Fixes: mesa/mesa#1207
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8334>
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