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Managing monitors in Void Linux

One of the things I'm most proud of is the script I wrote for managing monitors when I switched to Linux. 🖥️🐧

At first, I tried a few desktop environments, but I quickly realized I didn’t want just another “Windows” experience (with all due respect). So I decided to try my luck with other distros and focus more on window managers rather than full desktop environments. Long story short, I landed on Void Linux, an absolutely amazing distro, and experimented with three window managers that I really loved:

DWM by Suckless
Ultra-minimalist and super fast, with incredibly low battery usage. The configuration isn't very beginner-friendly, but it’s quite straightforward once you get the hang of it. The biggest drawback is having to recompile every time you change something. And since it’s so minimal, you’ll likely need to apply a few patches—which isn’t always easy.
StumpWM
This one’s written in Lisp. Ever since I discovered Emacs, I’ve been a Lisp fan, and I really like how customizable StumpWM is—it integrates beautifully with Emacs. The downside is its relatively high battery consumption, and occasionally, updates can break your setup if you have a complex configuration.
EXWM
This is basically Emacs acting as your window manager. If you’re already comfortable with Emacs, this is a fantastic option (though its setup can get a bit tricky). The main issue is: if Emacs crashes due to a heavy task, your whole window manager goes down with it.

So, I happily switch between these three depending on my mood—and battery level 😄

One of the downsides of moving away from full desktop environments is that they usually come with built-in utilities for things like multi-monitor setups. So, when I first went to the office and plugged in an external monitor, I found myself juggling a bunch of commands just to get it working properly. And then… the same thing happened at home. Things got even messier when a second laptop came into the picture.

Since I’m not a fan of repeating myself, I started thinking about how to automate the whole thing with a script that could detect whether I was at home or in the office and configure the monitors accordingly. I also wanted it to handle wallpapers.

It wasn’t an easy task. I’ll share a diagram below and then walk you through the code. 🚀

hotplug_monitor.svg
Figure 1: Hotplug Monitor Diagram

The code

Let's start initializing some of the variables and putting a loggin function.

#!/bin/bash

MYTAG="hotplug"
STUMPISH_CMD="/home/cnoceda/Qsync/config/bin/stumpish"
host_name=$(hostname)

function write_log(){
        logger -p user.info -t $MYTAG $1
}

The connect function should be called connect2 because it manages the 2 monitor connection. The variable shaHdmi has the id of the monitor. This id it's different for each monitor and helps us detect if we're at the office or at home. The variable $MAX_MODE has the resolution of the main laptop screen, because I’ve got 2 laptops with different resolutions. It’s set at the beginning of the script, down below.

At the office, the second monitor is on the left, so it's configured using the --pos argument.

function connect(){
        case "$shaHdmi" in
                "ba86bc9e7462cb06ec4646c2b3752a64d349d7d4") # Office PC
                        write_log "En Oficina PC"
                        /usr/bin/xrandr --output ${secundario} --mode 1920x1080 --pos 0x0 --scale 1.5x1.5 --output ${principal} --primary --pos 0x1620 --mode ${MAX_MODE}
                        ;;

This code is obsolete. It was the configuration through the dock station at home. But yeah, same idea.

"da39a3ee5e6b4b0d3255bfef95601890afd80709") # En casa con la Dock ¡¡SIN USO!!
        /usr/bin/xrandr --output ${principal} --primary --auto --output ${secundario} --auto --left-of ${principal}
        ;;

Here’s the configuration with the monitor above the laptop.

"c4a2e9b82a2d728fb785dcde3782e1bfbae5910e") #en casa Dell
        write_log "En casa Dell"
        /usr/bin/xrandr --output ${principal} --primary --mode ${MAX_MODE} --pos 0x0 --output ${secundario} --mode 1920x1080 --pos ${MAX_MODE:0:4}x0 --scale 1.5x1.5
        ;;

And finally, the default configuration using --auto for both.

*) # Por defecto arriba
                        write_log "Por defecto"
                        /usr/bin/xrandr --output ${principal} --auto --output HDMI-1 --auto --above ${principal}
                        ;;
esac

Here’s a tricky part. To make things work nicely in EXWM, I have to set some variables in elisp and read them in Emacs' init.el. I use a file to import them.

        echo -e "(setq exwm-randr-workspace-monitor-plist '(1 \"${secundario}\" ))\n;; Set the default number of workspaces as monitors.\n(setq exwm-workspace-number 2)" > ~/.config/emacs/exwm_monitors.el
}

With 3 monitors it’s basically the same, just… more cables 😅

function connect3(){
        case "$shaHdmi" in
                "ba86bc9e7462cb06ec4646c2b3752a64d349d7d4") # Office PC
                        /usr/bin/xrandr --output ${principal} --auto --primary --pos 1800x2470 --output ${tercero} --auto --rotate left --scale 1.5x1.5 --pos 0x0 --rate 59.95 --output ${secundario} --mode 1920x1080 --pos 1800x850 --rotate normal --scale 1.5x1.5 --rate 59.94
                        ;;
                "abccd4f93f27bc1849fc141e78c3905be8e890ed") # En casa
                        /usr/bin/xrandr --output ${principal} --primary --auto --output DP-3 --auto --left-of ${principal}
                        ;;
                "c4a2e9b82a2d728fb785dcde3782e1bfbae5910e") #en casa Dell
                        /usr/bin/xrandr --output ${principal} --primary --auto --output ${secundario} --auto --right-of ${principal} --scale 1.5x1.5
                        ;;
        ,*) # Por defecto arriba
                        /usr/bin/xrandr --output ${principal} --auto --output HDMI-1 --auto --above ${principal}
                        ;;
    esac
        echo -e "(setq exwm-randr-workspace-monitor-plist '(1 \"${secundario}\" 2 \"${tercero}\"))\n;; Set the default number of workspaces as monitors.\n(setq exwm-workspace-number 3)" > ~/.config/emacs/exwm_monitors.el
}

This function is used when I only have one monitor. Yeah, I know the name isn’t super clear. It basically disconnects everything except the main screen and sets the elisp vars too.

function disconnect(){
        # Obtener salidas
        disconnect_params=$(xrandr | grep -i "connected" | awk '{if ($2=="connected") { line = line " --output " $1 " --auto --primary"} else {line = line " --output " $1 " --off"}} END {print line}')

        write_log "disc: ${disconnect_params}"

        # Desconecto todo menos la principal
        /usr/bin/xrandr ${disconnect_params}
        echo -e "(setq exwm-randr-workspace-monitor-plist nil)\n;; Set the default number of workspaces as monitors.\n(setq exwm-workspace-number 1)" > ~/.config/emacs/exwm_monitors.el
}

Here's the beginning of the script. Logs some info and fills in some vars. As you can see, I grab all the data from xrandr.

write_log "Arrancando hotplug_monitor.sh"

case $host_name in
        void-slimx)
                MAX_MODE="2880x1800"
                ;;
        artix-slimx)
                MAX_MODE="2560x1600"
                ;;
        *)
                ;;
esac

NUM_MONITORS="$(xrandr | grep -i " connected "  | /usr/bin/wc -l)"
MONITORS=($(xrandr  | grep -i " connected " | awk '{print $1}' | tr '\n' ' '))

write_log "Monitores: ${NUM_MONITORS}"
write_log "Devs: ${MONITORS}"
write_log "mode: ${MAX_MODE}"

# Selección del nombre de las salidas. Cuando arranco con Intel las cambia.
principal=${MONITORS[0]}
secundario=${MONITORS[1]}
tercero=${MONITORS[2]}

write_log "Principal: ${principal}"
write_log "Segundo: ${secundario}"
write_log "Tercero: ${tercero}"

I use udevadm to query the udev database and get the GPU path. Usually it’s card0 but I’ve got a laptop with 2 graphic cards, so sometimes it’s card1.

# Modificación para arch-linux
syspath=$(/usr/bin/udevadm info -q path -n /dev/dri/card0)

if [ -z $syspath ]; then
        syspath=$(/usr/bin/udevadm info -q path -n /dev/dri/card1)
fi

Now, using the sys path, we get the monitor ID. The ? wildcard is used because of the card differences. Also, HDMI sometimes shows up as HDMI, sometimes as HDMI-1, so I slice with ${secundario:0:4}. Then I log it, in case I need to debug stuff later.

cardPath=/sys${syspath}

if [ ${secundario:0:4} == "HDMI" ]; then
        shaHdmi=$(/usr/bin/sha1sum $cardPath/card?-HDMI*/edid | /usr/bin/cut -f1 -d " " | head -n1)
        shacmd="/usr/bin/sha1sum $cardPath/card?-HDMI/edid"
else
        shaHdmi=$(/usr/bin/sha1sum $cardPath/card?-${secundario:0:4}/edid | /usr/bin/cut -f1 -d " " | head -n1)
        shacmd="/usr/bin/sha1sum $cardPath/card?-${secundario}/edid"
fi

write_log "cardPath: ${cardPath}"
write_log "shacmdr: ${shacmd}"
write_log "shaHdmi: ${shaHdmi}"

Let’s check which monitors are connected. status_2 and status_3 hold the info.

# MODIFICACIÓN para arch-linux
if [ "${secundario:0:4}" == "HDMI" ]; then
        status_2=$(cat /sys/class/drm/*-${secundario:0:4}*/status)
        write_log "status_2 ${secundario:0:4}: ${status_2}"
fi

if [ "${tercero}" != "" ]; then
        status_3=$(cat /sys/class/drm/*-${tercero:0:-2}*/status)
        write_log "status_3 ${tercero}: ${status_3}"
fi

Now we handle unplugging monitors properly. Sometimes xrandr gets confused if you don't do it cleanly.

# Desactivo por completo la pantalla principal y dejo solo la externa, si HDMI conectado
if [ "${status_3}" = "connected" ]; then
        write_log "Desconectando ${secundario} y ${tercero}"
        xrandr --output ${principal} --auto --primary --output ${secundario} --off --output ${tercero} --off
        sleep 3
elif [ "${status_2}" = "connected" ]; then
        write_log "Desconectando ${secundario}"
        xrandr --output ${principal} --auto --primary --output ${secundario} --off
        sleep 3
fi

With all that info in place, let’s plug things in and call refresh-heads in stumpwm (yes, twice—don’t ask 😅).

# Selecciono la conexion en caso de tener 1 o 2 monitores externos.
case ${NUM_MONITORS} in
        "3")
                write_log "Conectando 3 monitores..."
                connect3
                # Si arranco con Stumpwm...
                if [ "$(/usr/bin/pidof stumpwm)" != ""  ] ; then
                        write_log "Configurando Stumpwm..."
                        echo '(refresh-heads)' | ${STUMPISH_CMD} -e eval
                        ${STUMPISH_CMD} refresh-mode-line
                        echo '(refresh-heads)' | ${STUMPISH_CMD} -e eval
                fi
                ;;
        "2")
                write_log "Conectando 2 monitores..."
                connect
                # Si arranco con Stumpwm...
                if [ "$(/usr/bin/pidof stumpwm)" != ""  ] ; then
                        write_log "Configurando Stumpwm..."
                        echo '(refresh-heads)' | ${STUMPISH_CMD} -e eval
                        ${STUMPISH_CMD} refresh-mode-line
                        echo '(refresh-heads)' | ${STUMPISH_CMD} -e eval
                fi
                ;;
        "1")
                write_log "Conectando 1 monitor..."
                disconnect
                # Si arranco con Stumpwm...
                if [ "$(/usr/bin/pidof stumpwm)" != ""  ] ; then
                        write_log "Configurando Stumpwm..."
                        echo '(refresh-heads)' | ${STUMPISH_CMD} -e eval
                fi
                ;;
        *)
                exit
                ;;
esac

write_log "Finalizando hotplug_monitor.sh"

Thanks a ton for making it all the way through this long-ass post 🙏 If you’ve got any questions, feel free to reach out on Mastodon or DeltaChat 🚀

Comments in 🐘 Mastodon or XMPP text or in 📺 Fediverse.tv channel.

Author: Carlos Noceda

Date: 2025-03-27

Emacs 30.1 (Org mode 9.7.11)