display-setup-script does not execute on resume from sleep

[o-alquimista]

/etc/lightdm/lightdm.conf.d/99-dpms.conf:

[Seat:*]
display-setup-script=/usr/local/bin/dpms-enable

The script makes the screen turn off after 30 seconds of inactivity, to work around this bug in elementary OS.

/usr/local/bin/dpms-enable:

#!/bin/sh

(sleep 5; xset dpms 0 0 30) &

It's running as expected in all but one situation: when you suspend and resume the system while at the greeter.

Apparently, resuming from suspend resets the DPMS settings to default and does not trigger a display-setup-script to correct it.

lightdm 1.30.0 on elementary OS 8.1 (based on Ubuntu 24.04).

[o-alquimista]

All I get from its debug logs at the moment the system is resumed is this:

lightdm[19964]: [+1176.52s] DEBUG: Continue authentication