xfwm: Setting `--vblank=off` as a user

[Olivier Fourdan]

Hi,

On Thu, 4 Oct 2018 at 15:18, Paul Menzel <pmenzel+xfce at molgen.mpg.de> wrote:
> With
>
> ```
> $ xfwm4 --version
>         This is xfwm4 version 4.13.1 (revision 942156e4) for Xfce 4.12

So you're build predates and does not feature the fix for GL vblank
(commit 0e6b940/bug #14564)

>         Released under the terms of the GNU General Public License.
>         Compiled against GTK+-3.22.30, using GTK+-3.22.30.
>
>         Build configuration and supported features:
>         - Startup notification support:                 Yes
>         - XSync support:                                Yes
>         - Render support:                               Yes
>         - Xrandr support:                               Yes
>         - Xpresent support:                             No

And your build is incomplete, Xpresent should be the default but it's
not enabled in your build.

>         - Embedded compositor:                          Yes
>         - Epoxy support:                                Yes
>         - KDE systray proxy (deprecated):               No
> ```
>
> one of our users has an issue with the amdgpu graphics driver.

So you're defaulting to GL for vblank which is broken in the version you use.

> `xfwm4 --replace --vblank=off` works around that problem, so we would
> like to disable it, on only that system, and it’d be nice, if the
> users could do it themselves.
>
> Reading [1], it should be possible, but there is no option
> *Synchronize drawing to the vertical blank* in the tab *Compositor*
> in xfwm4-tweaks-settings.
>
> I am now going to configure it in `/etc/Xmor erecent11/xorg.conf.d/`, but it’d
> be great if the user could do it.

No, this is not meant to be a user option - Having an option to
"unbreak things" is usually suboptimal, I would advise to 1. enable
Xpresent in your build and 2. use a more current source tree for your
build.

Cheers,
Olivier