Xfce4: Automatic screen resize does not work when resizing SPICE client window

Publication date: 2022-04-08

Issue: Automatic screen resize does not work

Normally, with "spice-vdagent" installed, screen resolution of the guest is automatically adjusted so that it fits the resolution of the SPICE client window. However, since Xfce4 does not handle the resize events triggered when resizing SPICE client window, the screen resolution of the guest system is not adjusted automatically.

Solution: Resize with xrandr

Within a terminal window within the guest system, adjustment of screen resolution can be triggered manually like this:

xrandr --output Virtual-1 --auto

This can be automized by listening and reacting on resize events ourselves.

Create an ".xsessionrc" in your home directory in your guest system and start a script that does the job:

#!/bin/sh

if [ -x /usr/bin/spice-vdagent ] ; then
    /opt/scripts/observe_resizeevents.sh &
fi

Create the script ("/opt/scripts/observe_resizeevents.sh") like this:

#!/bin/sh

# Uses code from: https://superuser.com/questions/1183834/no-auto-resize-with-sp
ice-and-virt-manager

sleep 10

xrandr --output "$(xrandr | awk '/ connected/{print $1; exit; }')" --auto

xev -root -event randr | \
grep --line-buffered 'subtype XRROutputChangeNotifyEvent' | \
while read foo ; do \
    xrandr --output "$(xrandr | awk '/ connected/{print $1; exit; }')" --auto
done

This listens to the events. Whenever a relevant one is received, we trigger "xrandr" to adjust the screen resolution. Note that this is a nice example of the power of piping.

Hint towards the solution

Multiple users experienced the issue; but no solution for years: https://stackoverflow.com/questions/41990600/virt-manager-guest-resize-not-working
Two workarounds are posted here: https://superuser.com/questions/1183834/no-auto-resize-with-spice-and-virt-manager. The solution given above is a slight adaptation of the second workaround.