Xfce Forum

The Iron Wolf

Member

Registered: 2025-08-29

Posts: 11

[SOLVED] Black screen with mouse cursor on resume from lock

Hi,

I am running Xfce 4.18 with lightdm 1.30.0 and Nvidia 575.64.03 proprietary driver.  Sometimes, when I return from the lock screen, all I get is black screen and mouse cursor.  The only workaround is to restart desktop from TTY.   I am not sure if this is Xfce, lightdm or maybe even greeter used in Mint issue.

All kinds of suspend/sleep/display management is disabled in Power Manger.  However, when I lock my screen, after a while it gets turned off,  so somewhere some sort of power management is still happening.  I am new to Linux, so I would appreciate any inputs on how to diagnose this.

One interesting thing is that I found a way to reliably reproduce the issue:

*    reboot
*    login to desktop
*    lock using /usr/bin/dm-tool switch-to-greeter
*    unlock

Result is black screen with mouse cursor. 

Observations:

*    if I open few programs before locking, it does not happen anymore (only very rarely, so it still a problem). But with nothing opened it is 100% repro.
*    I replaced light-locker with /usr/bin/dm-tool switch-to-greeter in attempts to fix it.
*    nothing stands out in boot session log and xsession log is too noisy, hard to undertstand if it has hints to problem and I lack experience in Linux atm.
*    this does not seem to be related to Power Manager/Display tab settings - happens no matter what you set there.
*    not sure if related, but firefox often crashes upon return from lock screen.

Any suggestions appreciated.

Last edited by The Iron Wolf (2025-09-18 02:18:27)

eriefisher

Wanderer

From: ON, Canada

Registered: 2008-10-25

Posts: 940

Re: [SOLVED] Black screen with mouse cursor on resume from lock

Try removing light-locker all together. Replace with xfce4-screensaver.

---

But it's all right, when you're all in pain and you feel the rain come down
It's alright, when you find your way, then you see it disappear
It's alright....
Chris Cornell

The Iron Wolf

Member

Registered: 2025-08-29

Posts: 11

Re: [SOLVED] Black screen with mouse cursor on resume from lock

Try removing light-locker all together. Replace with xfce4-screensaver.

Thanks. Light-locker is removed and purged.  Do I have to use screensaver?

eriefisher

Wanderer

From: ON, Canada

Registered: 2008-10-25

Posts: 940

Re: [SOLVED] Black screen with mouse cursor on resume from lock

Not really. You can just have it blank the screen or shut it off entirely.

---

But it's all right, when you're all in pain and you feel the rain come down
It's alright, when you find your way, then you see it disappear
It's alright....
Chris Cornell

The Iron Wolf

Member

Registered: 2025-08-29

Posts: 11

Re: [SOLVED] Black screen with mouse cursor on resume from lock

Not really. You can just have it blank the screen or shut it off entirely.

Please, bear with me.  I am curious - how xfce4-screensaver is related to lock screen?   Does it run there?  Just trying to learn. 

My current understanding is that lock screen is handled by lightdm/sleek-greeter.   But even though I have Display management disabled in Power Options and light-locker removed from the system, something still shuts off the monitor while machine is locked, and I suspect this is the reason for at least some of my problems.

EDIT: found docs about screensaver, reading.

Last edited by The Iron Wolf (2025-09-16 21:43:20)

eriefisher

Wanderer

From: ON, Canada

Registered: 2008-10-25

Posts: 940

Re: [SOLVED] Black screen with mouse cursor on resume from lock

Xfce4-screen saver can also lock the screen if thats what you want. Or not.

Where did you switch the locking you mentioned earlier?

lock using /usr/bin/dm-tool switch-to-greeter

This could also be

dm-tool lock

---

But it's all right, when you're all in pain and you feel the rain come down
It's alright, when you find your way, then you see it disappear
It's alright....
Chris Cornell

The Iron Wolf

Member

Registered: 2025-08-29

Posts: 11

Re: [SOLVED] Black screen with mouse cursor on resume from lock

Xfce4-screen saver can also lock the screen if thats what you want. Or not.

Where did you switch the locking you mentioned earlier?

lock using /usr/bin/dm-tool switch-to-greeter

This could also be

dm-tool lock

I have keyboard shortcut for screen lock, and originally in Mint it had light-locker command there.  I read on this forum suggestions that light-locker causes black screen problem, and I removed it a while ago, but black screen still happens sometimes, and it happens reproducibly if I lock with no windows opened.

I am quite confused between all those components.  It sounds that I may not need lightdm at all, and instead use xfce4-screensaver.    If so, will I be able to stilll have same login screen UI (sleek-greeter?), which I like?

Last edited by The Iron Wolf (2025-09-16 22:02:37)

eriefisher

Wanderer

From: ON, Canada

Registered: 2008-10-25

Posts: 940

Re: [SOLVED] Black screen with mouse cursor on resume from lock

Lightdm is your login manager Light-locker is the screen locker. xfce4-screensaver can take care of the screen lock for you. light-lock have been problematic for years now. Unfortunately it's still a recommend for xfce4 packages, at least with Debian anyway.

If you want a graphical login manager keep Lightdm. You could also use GDM, KDM, SDDM............ Lightdm works just fine though. You can also login with startx/xinitrc. What greeter are you using?

---

But it's all right, when you're all in pain and you feel the rain come down
It's alright, when you find your way, then you see it disappear
It's alright....
Chris Cornell

The Iron Wolf

Member

Registered: 2025-08-29

Posts: 11

Re: [SOLVED] Black screen with mouse cursor on resume from lock

Lightdm is your login manager Light-locker is the screen locker. xfce4-screensaver can take care of the screen lock for you. light-lock have been problematic for years now. Unfortunately it's still a recommend for xfce4 packages, at least with Debian anyway.

If you want a graphical login manager keep Lightdm. You could also use GDM, KDM, SDDM............ Lightdm works just fine though. You can also login with startx/xinitrc. What greeter are you using?

I removed light-locker from my system a while ago.  So, occassional black screen with mouse cursor is not caused by that, it is something else.

I believe, I am using slick-greeter for greeter.  This is what I got with Mint 22.1 Xfce.  I tried some other login screens (I don't remember the details), but they are just a bit too much 90s vibe even for me

Let's zoom on one thing.  If I have Display management/Suspend disabled in Xfce Power Manager, which component turns screen off while system is locked?  Is it lightdm?  I am asking, because even though I doubt that is the reason for black screen (see my first post if curious), I have another problem - on resume from lock Firefox crashes, and I suspect it has to do with some sleep/suspend state, and that stuff is problematic even on Windows.

Last edited by The Iron Wolf (2025-09-16 22:18:39)

eriefisher

Wanderer

From: ON, Canada

Registered: 2008-10-25

Posts: 940

Re: [SOLVED] Black screen with mouse cursor on resume from lock

If you have sleep/suspend shut off then it shouldn't have an effect. Likely just hardware blanking the screen. It's possible that the desktop is crashing. Look into the .xsession-errors and .xsession-errors.old if after a restart.

---

But it's all right, when you're all in pain and you feel the rain come down
It's alright, when you find your way, then you see it disappear
It's alright....
Chris Cornell

The Iron Wolf

Member

Registered: 2025-08-29

Posts: 11

Re: [SOLVED] Black screen with mouse cursor on resume from lock

If you have sleep/suspend shut off then it shouldn't have an effect. Likely just hardware blanking the screen. It's possible that the desktop is crashing. Look into the .xsession-errors and .xsession-errors.old if after a restart.

Thanks for all your help so far.   Will update this thread if I figure anything out.

Added later 14 h 57 min 15 s:
So, some update from my side.  At least the reproducible black screen problem seems to get fixed by adjusting vblank setting mentioned here: https://forum.xfce.org/viewtopic.php?id=13233 Right under my nose

I still had black screen happen once, when my screen got blanked based on time set in Power Manager.  After unblanking, black screen and cursor. 

Now, I am trying to understand how to configure the time it takes for slick-greeter to turn off the screen after locking (and how to configure what it does, blank, suspend or turn off).   But, this is more of a Mint issue, not Xfce I guess

Gonna resolve this thread after a while.  Just want to make sure vblank xpresent actually is usable.

Last edited by The Iron Wolf (2025-09-17 13:40:56)

The Iron Wolf

Member

Registered: 2025-08-29

Posts: 11

Re: [SOLVED] Black screen with mouse cursor on resume from lock

For the screen locker timeout configuration, this worked perfectly: https://askubuntu.com/a/1104341/2330510 One caveat - mistakes in this can prevent booting, so be warned.