How do I wait for vertical retrace?

[Johan Walles]

2008/5/6 Samuel Thibault <samuel.thibault at ens-lyon.org>:
> 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, that sounds like *exactly* what I was after.

I don't care about vertical retrace in itself, waiting for vertical
retrace would only be a way for me to achieve flicker-free animation
in a 2D application.  Any other way of doing that would be fine as
well.

  Regards //Johan