kiosk-screen: toggle by DPMS state, and print the state it set

X wakes the monitor on any key press, so by the time the Del key reaches the backend
the monitor is already on and a toggle going by the monitor would switch it straight
back off. Only `off` ever enables DPMS, so toggle goes by that instead. on/off now
print the state they set, which the backend uses for its blubb's direction.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

roles/pi_kiosk/templates/kiosk-screen.j2

@@ -11,6 +11,13 @@
 # .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
@@ -21,24 +28,30 @@ 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 "$1" in
     on) screen_on ;;
     off) screen_off ;;
-    toggle) if [ "$(status)" = off ]; then screen_on; else screen_off; fi ;;
-    status) ;;
+    toggle) if switched_off; then screen_on; else screen_off; fi ;;
+    status) status ;;
     *)
         echo "usage: $0 on|off|toggle|status" >&2
         exit 2
         ;;
 esac
-status