Hazel's Zone

[Unit]
Description=Folding@Home Client
After=graphical.target
Requisite=graphical.target
After=multi-user.target
Requisite=multi-user.target

[Service]
Environment=EXTRA_OPTS=
Environment=ENABLE=true
EnvironmentFile=-/etc/default/fahclient
Type=idle
StateDirectory=fahclient
WorkingDirectory=/var/lib/fahclient
PIDFile=/run/fahclient.pid
PassEnvironment=ENABLE
# Make sure ENABLE is set to true in /etc/defaults/fahclient. This is here
# to emulate the behavior of the original init.d script.
ExecCondition=sh -c '[ "x$ENABLE" = "xtrue" ] || exit 255'
User=fahclient
ExecStartPre=/bin/sleep 10
ExecStart=/usr/bin/FAHClient /etc/fahclient/config.xml --pid-file=/run/fahclient.pid --pid
ExecReload=kill -SIGUSR1 $MAINPID
KillMode=mixed
TimeoutStartSec=20
TimeoutStopSec=10
Restart=on-abnormal
RestartSec=60

[Install]
WantedBy=graphical.target

#!/bin/bash

IDLE=300 # time in seconds

function have_command {
    # Determine if we have a command/alias/function/bash builtin
    # without running it.
    # || return $? protects us from set -o errexit
    type -t "$1" >/dev/null || return $?
}

function die {
    echo Error: "$@" >&2
    exit 1
}

function find_xauths {
    # Find X11 servers by looking for the -auth argument passed to them.
    # We need this info to connect to them anyway.
    # -Aww causes ps to print out All procs, and not cut off args (-ww)
    # -o args causes ps to only print out argument strings
    # The filename given after -auth is matched & printed by grep
    # -P is PCRE, allowing us to use negative-width lookbehind assertions
    # (?<=)
    # If this fails, it's probably because there's no X11s running,
    # the script will crash and systemd will restart it to try again later
    ps -Aww --no-headers -o args | grep -o -P -- '(?<=-[a]uth )\S+'
}

function check_idle {
    local f
    local dpy
    # Use 2^31-1 as a canary value to make sure we found at least one X server
    local -i int_max=2147483647
    local -i min_idle=int_max
    for f in $( find_xauths )
    do
        # xauth will retrieve the magic cookie X authority file, and tell us
        # what display its for (and how to connect to it)
        # in the first column, whcich we isolate with cut
        for dpy in $( xauth -f "$f" list | cut -d' ' -f 1 )
        do
            # Despite everything I can see online indicating that a 
            # display value of DISPLAY=host/unix:0 should work, it doesn't,
            # so if the display reported by xauth has that format, we just
            # cut it down to something like :0 by removing the */unix prefix.
            export DISPLAY="${dpy##*/unix}"
            export XAUTHORITY="$f"
            local -i idle
            # Use xprintidle to get us the idle time in milliseconds
            if idle="$(xprintidle 2>/dev/null)" ; then
                # Convert milliseconds to seconds
                idle=$(( idle / 1000 ))
                # Record the idle time in seconds of the least idle X server
                if ((idle < min_idle)) ; then
                    min_idle=idle
                fi
            fi
        done
    done
    if (( min_idle > IDLE && min_idle < int_max )) ; then
        # echo "Idle for $min_idle seconds, starting FAHClient"
        systemctl start FAHClient
    else
        # echo "Idle for $min_idle seconds, stopping FAHClient"
        systemctl stop FAHClient
    fi
}

function main {
    set -o nounset
    set -o pipefail
    set -o errexit

    if ! have_command xprintidle ; then
        die "Need xprintidle"
    fi

    if [[ ! -v IDLE ]] ; then
        IDLE=300 # seconds
    fi

    # Every 10 seconds, we check if all the X servers are idle
    while sleep 10 ; do
        check_idle
    done
}

# using a main function forces bash to read the entire file before doing
# anything, which is necessary because bash reads scripts line by line
# otherwise so if the script file changes while its running, strange stuff
# can happen
main "$@"

[Unit]
Description=Folding@Home Client Idler
After=graphical.target
Requisite=graphical.target
After=multi-user.target
Requisite=multi-user.target

[Service]
Environment=ENABLE=true
EnvironmentFile=-/etc/default/fahclient
Type=idle
PassEnvironment=ENABLE
ExecCondition=sh -c '[ "x$ENABLE" = "xtrue" ] || exit 255'
ExecStart=/opt/fahidle.sh
Restart=always
RestartSec=60

[Install]
WantedBy=graphical.target

systemctl daemon-reload
systemctl disable FAHClient
systemctl stop FAHClient
systemctl enable FAHIdle
systemctl start FAHIdle