Manual Implementation of Auto Resizing For Non-Gnome Environments (like XFCE) running under Spice/Libvirt

x-resize

#!/bin/bash
# Steps:
# 1) Make sure bash is available
# 2) Create udev rule
# - path to new udev rule: /etc/udev/rules.d/50-x-resize.rules
# - udev rule content: 
# ACTION=="change", KERNEL=="card[0-9]*", SUBSYSTEM=="drm", RUN+="/usr/local/bin/x-resize" 
# 3) Create /var/log/autores directory
# 4) Create script /usr/local/bin/x-resize (this file) and make executable
# 5) Reload udev rules with `sudo udevadm control --reload-rules`
# 6) Make sure auto-resize is enabled in virt-viewer/spicy
# 7) Make sure qemu-guest-agent spice-vdagent xserver-xspice xserver-xorg-video-qxl  are installed
# 8) Make sure spice-vdagentd is loaded and running fine
# Debugging:
# - Watch udev events on resize with `udevadm monitor`
# - Watch dmesg (may not be super useful) with `dmesg -w`
# - Watch autores logs with `tail -f /var/log/autores/autores.log`
# Credits:
# - Credit for Finding Sessions as Root: https://unix.stackexchange.com/questions/117083/how-to-get-the-list-of-all-active-x-sessions-and-owners-of-them
# - Credit for Resizing via udev: https://superuser.com/questions/1183834/no-auto-resize-with-spice-and-virt-manager

## Only run as root user
if [ "${EUID}" -ne 0 ]; then
    >&2 echo "Please run as root."
    exit 1
fi

## Ensure Log Directory Exists
LOG_DIR=/var/log/autores;
if [ ! -d $LOG_DIR ]; then
    mkdir $LOG_DIR;
fi
LOG_FILE=${LOG_DIR}/autores.log

## Function to find User Sessions & Resize their display
function x_resize() {
    declare -A disps usrs
    usrs=()
    disps=()

    for i in $(users);do
        [[ $i = root ]] && continue # skip root
        usrs[$i]=1
    done

    for u in "${!usrs[@]}"; do
        for i in $(ps e -u "$u" | sed -rn 's/.* DISPLAY=(:[0-9]*).*/\1/p');do
            disps[$i]=$u
        done
    done

    for d in "${!disps[@]}";do
	    session_user="${disps[$d]}"
	    session_display="$d"
	    session_output=$(su - "$session_user" -c "PATH=/usr/bin DISPLAY="$session_display" xrandr | awk '/ connected/{print \$1; exit; }'")
	    echo "Session User: $session_user" | tee -a $LOG_FILE;
	    echo "Session Display: $session_display" | tee -a $LOG_FILE;
	    echo "Session Output: $session_output" | tee -a $LOG_FILE;
	    su - "$session_user" -c "PATH=/usr/bin DISPLAY="$session_display" xrandr --output "$session_output" --auto" | tee -a $LOG_FILE;
    done
}

echo "Resize Event: $(date)" | tee -a $LOG_FILE
x_resize