problems with swapbuffers() on a VGX

[Ron Janzen]

I am having a peculiar problem with the swapbuffers() call on our
320/VGX running 3.3.2.  I was wondering if anybody else has seen this
problem. When our application runs in color map mode on the VGX,
swapbuffers seems to behave properly. However when we run in RGB mode,
swapbuffers() doesn't appear to wait for the vertical retrace before
swapping the buffers (ie. there is a tear across the screen).  If I put
a gsync() in front of the swapbuffers() the tearing goes away.  This is
kind of grudgy since it would slow things down on systems that don't
have this problem. We don't call swapinterval() anywhere in the code.
I tried explicitly calling swapinterval(1) before the swapbuffers().
This didn't help. The funny thing is that other (smaller) applications
that I have that run in doublebuffered RGB seem to work OK. I have also
run the identical code on a PI with Turbo option and a 70/GT and it
didn't exhibit the same behaviour. Does anybody know of any combination
of GL calls that could invoke this kind of behaviour?

There is some mention in the 3.3.2 release notes of a bug in swapinterval()
on VGX's that was fixed in 3.3.2. Perhaps there is still a problem in
there somewhere.

Ron Janzen
Alias Research Inc., Toronto
rjanzen%alias at csri.utoronto.ca