xdg-open-current-seat

#!/bin/bash
# yes - bash - because <() is really nice to have in a while read loop

set -e

SESSIONS="$(loginctl list-sessions --no-legend)"
SEAT=""
while read session; do
    maybe="$( echo $session|cut -f4 -d" " )"
    if [ -z "$maybe" ]; then
        continue 
    fi
    if [ -n "$SEAT" ] && [ "$maybe" != "$SEAT" ]; then
        echo "cannot continue, found multiple seats: $SEAT and $maybe"
        exit 1
    fi
    SEAT="$maybe"
done < <(echo "$SESSIONS")
if [ -z "$SEAT" ]; then
    echo "cannot find a seat"
    exit 1
fi

SESSION_ID="$(echo $SESSIONS | cut -f1 -d" ")"
SCOPE="$(loginctl show-session -pScope --value "${SESSION_ID}")"
SESSION_UID="$(loginctl show-session -pUser --value "${SESSION_ID}")"

CGROUP="$(systemctl show  -pControlGroup --value "$SCOPE")"

# this is where it gets ugly
cat /sys/fs/cgroup/pids/"$CGROUP"/cgroup.procs |while read pid; do
    ENV="$(cat /proc/"$pid"/environ | tr '\0' '\n')"
    if echo "$ENV" | grep -q '^XAUTHORITY='; then
        # found a env with the right env, copy it
        envstr=""
        while read line; do
            envstr="--setenv=$line $envstr"
        done < <(echo "$ENV")
        systemd-run --scope  --uid="$SESSION_UID" $envstr xdg-open "$1"
        break
    fi
done