How do I wait for vertical retrace?

[Samuel Thibault]

Michel Dänzer, le Tue 06 May 2008 09:37:23 +0200, a écrit :
> On Mon, 2008-05-05 at 15:43 +0100, Samuel Thibault wrote:
> > Michel Dänzer, le Mon 05 May 2008 10:22:19 +0200, a écrit :
> > > On Sun, 2008-05-04 at 20:06 +0200, Johan Walles wrote:
> > > > 
> > > > I would like to wait for vertical retrace in an X application.  How
> > > > can I do that?
> > > > 
> > > > The point would be to avoid flicker in my app by using double
> > > > buffering and update the on-screen image during vertical retrace.
> > > 
> > > There's no mechanism for this yet in X. Your best bet is probably to use
> > > OpenGL, e.g. the GLX_SGI_swap_control extension.
> > 
> > Isn't there a more simple double buffering X extension?
> 
> You mean DOUBLE-BUFFER?

Yes.

> I'm not really familiar with it, but I know that
> at this time it can't synchronize buffer swaps to the refresh.

Eww, that would be a pity.  At the very beginning of the Extension
documentation (Johan: xspecs/Xext/buffer.PS), it is said `Clients should
be able to [...] Display a series of buffers in a window in rapid
succession to achieve a /smooth/ animation', which is what Johan wants
to eventually achieve AIUI (vertical retrace wait being only one method,
I don't know whether which others could be possible).

Samuel