Present extension and TearFree on Intel

[Keith Winstein]

Thanks, Keith. Unfortunately UXA (with TearFree off) shows the same problem
-- a tear that slowly moves down the screen over the course of a few
seconds, then repeats soonafter. The application still sees the idle events
at the correct rate with jitter < 1 ms; it's just the on-screen display
shows the tear.

Do you think there is a workable option for us, from the client
application's perspective (or that this is likely to be fixed in future
versions of the X server)? We don't really want to tell users to muck with
their xorg.conf to turn on TearFree. Of course we can certainly switch back
to using OpenGL -- it's just that the Present API is so attractive!

I'm also happy to try to get my hands dirty with debugging it if you have
some suggestions for where to start looking.

Thanks,
Keith

On Tue, Nov 11, 2014 at 3:19 PM, Keith Packard <keithp at keithp.com> wrote:

> Keith Winstein <keithw at cs.stanford.edu> writes:
>
> > Hello all,
> >
> > First off, thank you for making the Present extension -- it looks like a
> > very welcome addition to X11.
> >
> > I am trying to use PresentPixmap to display a pixmap in
> vblank-synchronized
> > manner with Xorg 1.15.1, xserver-xorg-video-intel 2:2.99.910-0ubuntu1.2,
> > and Intel HD Graphics 3000, but in practice we see lots of tearing unless
> > we enable the "TearFree" option. This does not seem to be the default
> with
> > a blank xorg.conf.
>
> You might want to switch to UXA acceleration; the default SNA has
> significant problems with DRI3.
>
> > By contrast, OpenGL code that uses the swap interval extensions works
> great
> > out of the box.
>
> that's good to hear!
>
> --
> keith.packard at intel.com
>
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