#!/bin/sh
# Managed by ansible (pi_kiosk role).
#
# kiosk-screen on|off|toggle|status - switch the kiosk's monitor on or off.
#
# "Off" is DPMS: X stops the HDMI signal and the monitor drops into standby. The
# session, the browser and everything playing carry on. The MusicMouse backend runs
# `kiosk-screen toggle` for the IR remote's power key (its config's screen: section);
# it works over ssh as root too.
#
# .xinitrc turns DPMS off so the screen never blanks by itself. Forcing it off has to
# turn DPMS on, so `on` turns it back off again - otherwise the screen would blank on
# its own ten minutes after every switch-on.
#
# `toggle` therefore goes by whether DPMS is enabled, not by whether the monitor is lit:
# only `off` ever enables it. That matters for the keyboard. X wakes the monitor on any
# key press, so by the time the browser hands the Del key to the backend the monitor is
# already on again - going by that, toggle would switch it straight back off. Going by
# DPMS, the press reads as "switch on", which is what it was. (Woken by any other key,
# the screen stays on until the next toggle, which then makes the "on" stick.)

set -e
export DISPLAY=:0
export XAUTHORITY=/home/{{ pi_kiosk_user }}/.Xauthority

# With DPMS disabled `xset q` prints no monitor line at all, and the monitor is on.
status() {
    if xset q | grep -q "Monitor is Off"; then echo off; else echo on; fi
}

switched_off() {
    xset q | grep -q "DPMS is Enabled"
}

# Each prints the state it set: the backend picks the blubb's direction from that word.
screen_on() {
    xset dpms force on
    xset -dpms
    echo on
}

screen_off() {
    xset +dpms
    xset dpms force off
    echo off
}

case "$1" in
    on) screen_on ;;
    off) screen_off ;;
    toggle) if switched_off; then screen_on; else screen_off; fi ;;
    status) status ;;
    *)
        echo "usage: $0 on|off|toggle|status" >&2
        exit 2
        ;;
esac