On Thu, 17 Jan 2002, Martin Pottendorfer wrote:
> hi,
>
> Mark Vojkovich [EMAIL PROTECTED] wrote on Wed, 16 May 2001 11:32:20 -0700 (PDT)
> > On Wed, 16 May 2001, Peter Ronnquist wrote:
> >
> > > Hello,
> > >
> > > I am trying to figure out how to update the screen
> > > during vertical retrace. Is this possible with Xfree?
> >
> > No. Not in any portable way. Only if the client knows
> > hardware specifics and runs as root and pokes registers.
> >
> > If you are using OpenGL, your OpenGL implementation may
> > be able to do buffer swaps synced to the retrace. Probably
> > not though.
> >
> > Mark.
>
> Sorry to quote a quite old posting.
> Just a short question related to the topic above:
>
> Isn't the following fairly portable without OpenGL (at least to
> architectures where DGA2 is available)?
Yes, if you want to be limited to running under DGA2.
It's not useful outside of DGA.
Mark.
>
> [ From README.DGA ]:
> void XDGASetViewport(
> Display *dpy,
> int screen,
> int x,
> int y,
> int flags
> );
> [...]
> viewportFlags
> Any of the following may be OR'd together:
> XDGAFlipRetrace
> Indicates that the hardware can switch viewports during
> the vertical retrace.
> XDGAFlipImmediate
> Indicates that the hardware can switch viewports immediately
> without waiting for the vertical retrace.
> [...]
>
> I'm using this to get smooth animations with DGA2, and to some extent
> it works. As it's not perfect (probably my fault) I'm still interested
> in this topic.
>
> thanx,
> martin
>
> PS: please CC to my address above, as I'm not subscribed to the Xpert
> list. Thanx.
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