Annoying error message when locking screen

[tsujan]

Expected Behavior

When the screen is locked correctly, no error message should be shown.

Current Behavior

An error message is shown with xscreensaver after unlocking the screen.

Possible Solution

Do we lock the screen twice?!

Steps to Reproduce (for bugs)

1. Install xscreensaver and start it.
2. Check LXQt Session Settings → Basic Settings → Lock screen before suspending/hibernating.
3. Log out and log in.
4. Close the lid of your laptop to suspend it (or suspend it in any way).
5. Open the lid (= resume). The system will be resumed and you could unlock the screen.

Then, after unlocking the screen, you'll see this dialog:

This is redundant because the screen was locked and unlocked correctly.

Context

See lxqt/lxqt#1803 (comment)

System Information

• Distribution & Version:
• Kernel:
• Qt Version:
• libqtxdg Version:
• lxqt-build-tools Version:
• Package version:

[tsujan]

@selairi, @yan12125, do you know why this happens?

[yan12125]

I follow your Steps to Reproduce and do not get the Screen Saver Error dialog after unlocking the screen.

If I lock the screen (not suspend) and run DISPLAY=:0 xscreensaver-command -lock from another tty, that command fails with "already locked" or "no response to command". So, a wild guess is that some other daemon has locked the screen and thus lxqt fails to lock it again.

[kmiernik]

Maybe this will help, but notice that it happens only with xscreensaver 5.44. WIth previous versions it is not. Secondly it happens only when suspend is called, try systemctl suspend, and simply unlock the screen.

[yan12125]

I have xscreensaver 5.44, and I've tried using systemctl suspend as well as suspending from lxqt-leave, and got no error messages in either cases. By the way I also use Arch :)

[tsujan]

So, the problem isn't as clear as it seemed to me and @kmiernik. There should be a hidden parameter somewhere — maybe, in xscreensaver.

I also have xscreensaver 5.42 and 5.43 in /var/cache/pacman/pkg; will test with them later.

[kmiernik]

My next guess for culprit is gdm. If I switch to lxdm I have no error message anymore. Perhaps it is locking the screen before the lxqt.

[tsujan]

My next guess for culprit is gdm.

I use sddm.

[yan12125]

I use sddm, too. tsujan <notifications@github.com> 於 2020年5月31日 週日 19:55 寫道：

…

My next guess for culprit is gdm. I use sddm. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#257 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAOZCGP5256ID6GALLDX2D3RUJASHANCNFSM4NO3EJ7Q> .

[tsujan]

On the computer I did tests, I have gdm too but it's disabled (I needed gdm to install gnome, in order to test some Qt apps under it).

I don't want to install xscreensaver on my main laptop (I'm working under its LXQt session) and can't uninstall gdm on my (older) test laptop (I need its gnome for tests). But I think, sooner or later, we'll find the cause and, most probably, it won't be in LXQt.

[yan12125]

Ah, found something interesting in xscreensaver

X11: On systemd systems, closing your laptop lid might actually lock your screen now, maybe.

(From changelog for version 5.43 on https://www.jwz.org/xscreensaver/changelog.html)

So I tried it - if I uncheck "Lock screen before suspending/hibernating", the screen is still locked after resuming from suspend.

Under the hood, a process xscreensaver-systemd listens to PrepareForSleep signal from systemd-logind (or maybe elogind or similar), and locks the screen. So, "some other daemon" might be xscreensaver itself :)

That also explains why the issue did not exist for older xscreensaver versions - systemd integration is new in xscreensaver 5.43.

[tsujan]

It makes perfect sense.

Then, I guess we don't need to do anything. If new versions of xscreensaver don't need our option, the error message shows the user that he/she should either disable xscreensaver's mechanism or, more easily, uncheck LXQt's option.

@yan12125, if you agree on that, then this issue could be closed.