bug#57068: Resizing mcron job in vm-image.tmpl interferes with settings

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

Hi Ludovic,

Ludovic Courtès <ludo@gnu.org> writes:

> Hi,
>
> Mathieu Othacehe <othacehe@gnu.org> skribis:
>
>>> Oh, I wasn’t aware of that, that should certainly be fixed.  (I fixed a
>>> similar issue in GNOME some years ago, and I’m confident it’ll be easier
>>> to fix in Xfce because it doesn’t have all those layers and daemons and
>>> JavaScript and DBus interfaces.  :-))
>>
>> Fixing this behaviour in Xfce seems like the right thing to do to
>> conserve SPICE support and fix the QEMU resizing issue.
>>
>> This also looks like a large development, so I propose to unblock the
>> release with this ticket.
>
> I agree, but it would be nice to find another workaround: invoking
> xrandr every second is undesirable.  It interferes with user settings
> and degrades performance, whether or not one uses SPICE.
>
> Can the guest determine whether SPICE is being used?  That would allow
> us to make the hack conditional.

I've discovered we could use udev to invoke xrandr only on resizing
events, crafted a custom Guile script, and used it to fix this with
commit 1d4db94bebba ("gnu: vm-image.tmpl: Improve SPICE dynamic
resizing.").

I've tested the automatic resizing works with virt-manager and GNOME
Boxes, and that nothing happens when using QEMU (the script still runs,
consuming 14 MiB of RSS about, but that's it).

-- 
Thanks,
Maxim