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I have screen energy saving enabled, but my monitors never turn off automatically - even when the screen is locked. I can -briefly- manually turn them off using xset dpms force off, but in a couple of seconds both of my monitors turn on again, without any interaction from me.

Is there a way to find out why this keeps happening? Can a running application do this, and if so, how would I identify the culprit?

OS is Debian 10 64-bit with KDE 5.

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  • Does dmesg hint at anything?
    – pfnuesel
    Aug 26, 2021 at 12:58
  • Some mice can generate movement events while laying on an even surface. Disconnect your mouse and check if it helps. Also, some applications can disable monitor power saving, e.g. video players like mpv. Aug 26, 2021 at 13:04
  • I've tried unplugging the mouse, and even unplugging the keyboard (immediately after sleep 5 && xset dpms force off), neither of which worked. dmesg output appears to contain nothing of relevance, neither do ~/.xsession-errors or /var/log/Xorg.0.log. I can't think of anywhere else to check. Aug 26, 2021 at 23:28
  • I had a similar problem in Ubuntu 2204 Gnome, on a 2021 model Asus laptop plugged into a Dell monitor. Take a look at my answer or some of the other answers on this thread: unix.stackexchange.com/a/704934/405507 Jun 3, 2022 at 23:20

2 Answers 2

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I dealt with this problem and it turned out that my monitor was set to "auto" for source. and each time the monitor was powered off via dpms, when it cycled for a new source it turned the monitor back on. I set the source from auto to the dedicated source (HDMI) and the problem was solved.

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  • That was it! I've had auto-off working fine for years. Today I switched my video card out and then this started to happen. They would go off but come back on. Apparently switching from HDMI to DP caused one of my monitors to default back to auto select. (seems I figured this out previously). Interestingly the other two monitors did not but they did not switch from HDMI to DP. Anyway, glad this was such as an easy fix.
    – Daniel R.
    Mar 29 at 19:06
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Of course the solution presents itself within a day of asking the question. While trying to fix an unrelated problem that someone has ran into before, I stopped the kscreen_backend_launcher process (using kill -STOP), and not only do my monitors go to and stay asleep properly, my desktop stops rearranging itself every time I turn my HDMI monitor off.

I don't know why that process wants to keep my monitors awake, but at least I now have a workaround.

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