frame-locking pipes and channels

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Drew Hess (dhess++at++vision.arc.nasa.gov)
Mon, 18 Jul 1994 18:06:55 -0700

I want to frame-lock multiple hardware pipes so that the pfPipes associated with
each hardware pipe swap buffers synchronously. From the man page for pfPipe:

     If you wish to frame lock multiple pfPipes so that each pfPipe swaps its
     color buffers at the same time, then you should create a channel group
     consisting of one or more pfChannels on each pfPipe and make sure
     PFCHAN_SWAPBUFFERS is shared.

     Example 1: How to frame lock pfPipes

        leftChan = pfNewChan(pfGetPipe(0));
        rightChan = pfNewChan(pfGetPipe(1));

        /* BPFCHAN_SWAPBUFFERS is shared by default */
        pfAttachChan(leftChan, rightChan);

        /* Pipe 0 and pipe 1 are now frame-locked */

What if I modify the code fragment above to look like this:

        leftChan1 = pfNewChan(pfGetPipe(0));
        rightChan1 = pfNewChan(pfGetPipe(1));
        leftChan2 = pfNewChan(pfGetPipe(0));
        rightChan2 = pfNewChan(pfGetPipe(1));

        pfAttachChan(leftChan1, rightChan1);

Since leftChan2 and rightChan2 are running on pipe 0 and pipe 1, respectively,
and since those pipes are frame-locked, does this mean that leftChan2 and
rightChan2 will also swap buffers at the same time as leftChan1 and rightChan1,
even though they're not part of the channel group that is sharing the
PFCHAN_SWAPBUFFERS attribute?

Thanks
-dwh-
dhess++at++vision.arc.nasa.gov

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