swaylock with blurred screenshot

lockscreen.bash

#!/bin/bash
# shellcheck disable=SC2086,SC2064
# vim: set ts=2 sw=2 tw=0 noet :

# Take screenshots, apply gaussian blur, lock screen
# grim -> blur -> swaylock
readonly GRIM=/usr/bin/grim
readonly BLUR="$HOME/bin/blur"

set -Eueo pipefail
# lock with safe config on error
trap "swaylock -feFKc 133337 -C /dev/null" ERR INT

scratch=$(mktemp -d /tmp/lockscreenshot.XXX)
trap "rm -rf ${scratch}" EXIT

# Build swaylock args
ARGS="--daemonize"

# Active monitors, not just .focused
for monitor in $(swaymsg -t get_outputs | jq -r '.[] | select(.active) | .name')
do
    img="${scratch}/${monitor}.png"
    {
        $GRIM -o "${monitor}" "${img}" &&
        $BLUR "${img}" "${img}" > /dev/null
    } &
    ARGS="$ARGS --image=${monitor}:${img}"
done

wait # for all screenhots to blur

exec swaylock $ARGS