I have an issue with the lockscreen behaviour in KDE Plasma that I think started happening since v6.4.
In System Settings > Power Management > Display and Brightness, I set “Turn off screen” to “when locked: 1 minute”. That worked as you would expect before I updated plasma. Now, here’s what happens when I lock my session:
after 1 minutes, the screen turns black
roughly 10 seconds later, it turns itself back on and shows the lock screen. At that point it stays on and won’t ever turn itself off again.
What’s particularly weird about this is that I usually use two screens together, and this only happens on one of the two screens. So, on screen A only, what I described above happens; on screen B only it works as expected (aka the screen does turn off after one minute on the lockscreen), and when both screens are connected screen B works normally but screen A still bugs out as described above. The two screens are new and were bought together, if that matters. The bugged screen is connected through hdmi, the working one through DP.
Writing this post made me think of a couple more things I could do to troubleshoot this and I think I’ve found something relevant: I described above that the buggy screen was connected via hdmi, well if I connect if through DP instead there’s no bug anymore. So it definitely looks related to hdmi somehow.
(I know that one workaround would be to use DP only but that’s not a possibility for me right now unfortunately as I don’t have a GPU, only the CPU’s integrated graphics, and my motherboard only has 1 hdmi and 1 DP outputs)
They do not unfortunately. And in any case this would not have been a fix nor explain the issue, but I appreciate you trying to find me workarounds in the meantime.
So after a bit more testing it looks like the issue has little or nothing to do with screenlocking, it’s just the “turn off screen” feature that is bugged. I tried setting that to 10min and screen locking to 20 to see what would happen if the screen goes to sleep before the session gets locked, and after 10 minutes I get the same behaviour described in the original post: hdmi screen never turns off, DP screen does. Even more troubling, the session never locks at that point for some reason (whereas in this testing it should have after 20min), it’s like something in this bug is preventing the locking to be triggered afterwards.
I had the same monitor setup as well (HDMI motherboard+ DP monitors), and did encounter the same bug… Its annoying I had to pull the HDMI cable out after the update since my screen do not want to turn off…