lqxt-config-monitor saved altered display resolution triggers display fade to black after system startup

[Menno den Hollander]

Steps to reproduce (verified on clean Lubuntu 18.10 install):
- Launch lxqt-config-monitor
- Alter display resolution, accept resolution
- Save configuration
- Restart pc
- Wait up to one minute

What happens:
- The display fades to black (Approximately 10 sec after showing the desktop background)
- (System is still reachable via the network (samba))

What should happen:
- Display shouldn't fade to black almost immediately after start-up

Workarounds:
- Don't save altered resolution, but set it each time manually on start-up
- Deleting the saved setting and restarting the PC doesn't make the issue appear again.

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: lxqt-config 0.13.0-0ubuntu5
ProcVersionSignature: Ubuntu 4.18.0-10.11-generic 4.18.12
Uname: Linux 4.18.0-10-generic x86_64
ApportVersion: 2.20.10-0ubuntu13
Architecture: amd64
CurrentDesktop: LXQt
Date: Fri Nov 2 22:58:36 2018
InstallationDate: Installed on 2018-10-26 (7 days ago)
InstallationMedia: Lubuntu 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.2)
SourcePackage: lxqt-config
UpgradeStatus: No upgrade log present (probably fresh install)

[ԜаӀtеr Ⅼарсһуnѕkі (wxl)]

Does this fade to black occur if you don't make the changes?

[Menno den Hollander (mennodenhollander)]

I am unsure what do you mean by "make the changes"? It only happens when I save a configuration and restart the pc. If I change the display resolution, but don't save it then it doesn't happen (neither immediately and neither after I restarting the PC). I hope this answers your question...

[ԜаӀtеr Ⅼарсһуnѕkі (wxl)]

Are you sure this isn't xscreensaver kicking in?

[ԜаӀtеr Ⅼарсһуnѕkі (wxl)]

Also: how long does it stay black?

[Menno den Hollander (mennodenhollander)]

I disabled screensaver (Mode, select Disable Screen Saver).

After it turns black, it stays black.

I have installed Lubuntu 19.04 and I noticed the same issue. However, I also noticed that the screen fades to black on if auto login is enabled. I searched the internet for autologin and black screen and it seems to be a common problem (unrelated to LXQt).