Plasma 6: Lock screen renders black (troubleshooting help)

I’m trying out Plasma 6 on my Arch install (using the testing repositories on Arch), and I have encountered one consistent issue (and a few inconsistent ones I’m not worried about right now). Whenever I lock my laptop - from putting the laptop to sleep, from the application launcher, or the keyboard shortcut - the lock screen renders black almost all the time. The cursor is visible, and the changing cursor indicates that things like the password field are present, but just isn’t being rendered. If I switch to a different TTY and switch back, the lock screen renders as normal. I can also unlock it still by typing in my password (blind) or using the fingerprint unlock, and the desktop will appear normally.

I figure this is a bug I should report (either make a new bug report or add a comment to an existing one), but I’m having trouble finding any troubleshooting information to provide about the issue. I’ve checked journalctl -r, but the only thing related to the lock screen I could see was a warning about a missing pam_pkcs11 module, but fixing that (by installing it from the AUR) did not fix the issue. What should I be checking to try and troubleshoot this? I would like to make an attempt to resolve this issue myself (if I can), or at least have some relevant information to provide to a bug report, but I just don’t know where to start. Any help would be appreciated.

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This sounds like Bug 481308. As mentioned in the bug report, I think we don’t have enough debug logs built into PowerDevil right now to effectively analyze the root cause. I believe PowerDevil’s DPMS action would trigger this behavior on X11, but I don’t know why. If I were able to reproduce it myself, I’d want to find out why it gets triggered, e.g. what’s the registered idle timeout when the screen goes black.

I’ll be honest, I thought I was using Wayland, but then when I went to double-check, I realized it was set to X11. I think I got my defaults messed up when messing with SDDM settings, which would explain why I only started seeing it after messing with SDDM. Now that I’m back on Wayland, the bug has disappeared. This does work for me, so that’s good to know. I’ll try to use it for a bit on wayland to see if the other issue(s) I noticed on X11 appear there before looking to make any bug reports for them.

Would it help if I add my system information to that bug report? I see it was reported by an AMD graphics user, while my system is using integrated intel graphics (the CPU is a i7-1165G7, for the record), and I also found Bug 477738 that sounds like it might be the same issue, just reported using an Nvidia GPU.

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Yes, I’d appreciate that extra info in the bug. I was wondering if my GPU is responsible for not being able to reproduce the bug here locally, looks like it’s something related to my setup instead.

Doesn’t sound like that to me. That bug report was on 5.27 Wayland and seems to have disappeared on 6.0 Wayland if I skimmed that correctly.


It’s possible this is a Neon packaging bug. See Black screen with cursor after updating KDE Neon to Plasma 6 - #4 by jsalatas.

Not sure it is a packaging issue. It seems to me like it is correlated with the wine32:i386 being installed. Maybe one additional test in future versions of kde neon is if a system with steam (and i386 architecture packages installed) can be upgraded without issues.

See also this KDE Neon cannot be installed wine winehq-stable - #7 by gusarg81

Same thing on Arch (upgraded from 5.27.10) with Xorg. Meta+L → Black Screen and the cursor. It’s OK with Wayland though.

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Isn’t it unsupported to get apps from the distro repos on Neon? I thought you were supposed to exclusively use Flathub and Snap.

Furthermore, while in black & cursor, if you press Esc the monitor switches off. (ofc entering the password brings up the desktop again).

I’m not sure what that means. In any case, if I’m not wrong, you need to explicitly enable the i386 architecture. Right? and my assumption is that by doing so you are on your own. However many users would do so when they try to install steam client, because the command sudo dpkg --add-architecture i386 is literally in every “how to install steam on ubuntu 22.04” tutorial.

It means on Neon you’re supposed to get your apps using Discover, not apt. apt shows you everything in the distro repos, and apps from there are deliberately hidden from Discover in Neon, to prevent people from getting them. So when you use apt anyway, you’re bypassing this and getting apps that have not been tested, have no QA, are not guaranteed to work, and could wreck the rest of the system by pulling in un-upgradable dependencies when installed.

Right, but Neon is not Ubuntu. It may be an Ubuntu-based distro, but it is not Ubuntu.

Also, I’m sure the Ubuntu folks themselves are not exactly thrilled about this! :smiley:

oh well! the apt thing is news to me! I only knew about the update that we should use either pkcon or discover. In any case I’m personally too bored to type commands so I use discover in any case.

However, imho there’s an elephant in the room hard to ignore and at least we should somehow warn users about it, like we warn them about the system updates in the FAQ

I absolutely agree, yeah.

Happens here too (Arch + Nvidia). After 10 to 15 seconds since moving the mouse the lock screen is actually rendered correctly. After unlocking, the screen turns black + cursor again, and after 10 to 15 seconds more the unlocked screen is rendered.

+1 for exact same issue. somethings not in the thread yet:

  • although it is black screen at login, the buttons are all there and you can click them, I was even able to login by noticing cursor change on hovering over the text box and typing in the password.

  • similarly for after logging in, all thing are there, I have set the top screen edge to go to “overview” and the overview render perfectly but coming back to screen; its black again

  • I have a different laptop which I have disable Nvidia GPU and over there the login screen does not recover and I need to logout and login again

I’m having the same issue. I’m on Arco Linux, logging on X11, and every time my screen locks out (or if I press Meta + L), I get the black screen with the mouse cursor. I found out that I can get the monitor back up if I spam ‘stamp’ button, but it doesn’t work super consistently (maybe I just need to spam it more, but I managed to unlock the screen and get back to my desktop a few times already by spamming it). This looks like a bug alright, given that it happens consistently with multiple people.

Hi all, just wanted to note that Plasma 6.0.2 is in the process of getting released right now. It contains some important fixes for the “turn off screen” behavior and I hope that most users will find this working as it should after the upgrade.

So, keep an eye out on your package sources and pick up those fixes as soon as possible. If anything is still broken after the update, please speak up again.

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There is also a bug on X11 if the Plasma Style is Breeze (follows color scheme).

Switching my Plasma Style to either Breeze Dark or Breeze Light fixes the issue for me.

This is still an issue with Plasma 6.0.2 on openSUSE Tumbleweed. I also noticed that it depends on the Plasma Style. With ‘Breeze’ or ‘Breeze dark’ the issue is present while the lock screen works as expected with ‘Breeze twilight’ and ‘openSUSE’.

Plasma Style

Bug 483163 for anyone who has insightful information to add that can help us track down the cause.