KDE desktop compositing occasionally causes strange visual artifacts. This includes the following problems, which may or may not be related:
- Certain panels flicker when rendering against other panels, which looks as if the two are z-fighting. I often see this with Skype notifications in the system tray as they interfere with the Plasma panel.
- The Plasma desktop no longer executes visual updates unless the user does an action that forces it to. For example: If you have an analog clock with the seconds hand enabled, you will notice that it's stuck and the hands aren't moving any longer... however if you switch desktops to force a redraw, the hands will move to represent the current time but only once at that moment. This problem is rare and always goes away after toggling desktop compositing.
- The contents of certain windows are no longer updated, and a past version of the window is drawn instead. I often think the application has frozen until turning off desktop effects and seeing that it updates again. This problem is rare and always goes away after toggling desktop compositing.
Since I don't know how much this is a KDE problem and how much it's the drivers, I'm reporting it with both of the teams. My OS is openSUSE Tumbleweed x64. Plasma 5.10.4, MESA 17.1.5, Kernel 4.11.8. My CPU is an Intel core i7 920, my video card is a Radeon R7 370 from Gigabyte (RadeonSI / GCN 1.0 / Pitcairn Islands) and I'm running the 'radeon' driver (no 'amdgpu' support yet).
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Screenshot of Skype notification flickering
Screenshot of a Skype notification glitching against the Plasma panel. This shows one frame of the interference, the pattern changes constantly causing flickering. Only edit includes removing the message contents from the white area.
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Output of "qdbus org.kde.KWin /KWin supportInformation"
Please attach the corresponding Xorg log file.
I do suspect that at least some of these are kwin issues. Do they not happen with the Xorg modesetting driver?
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Created attachment 133288 [details]
(In reply to Michel Dänzer from comment #3)
Attached both Xorg logs to be safe. I haven't played around with the drivers, as this is my main desktop and I can't risk a system that doesn't boot.
I'm still seeing this every now and then... very rarely, but apparently it will occur at certain times. I'm curious if anyone else is getting those issues and can confirm them. Is this even a KDE problem or a video driver bug?
Maybe a totally different code-path but I definitely have some moderate artifacting when I enable desktop effects and enough monitors on my RX480. The artifacting appears during desktop effects magic, i.e., during window drags, but goes away as soon as the magic stops.
Usually the artifacts are "medium" sized and always appear on a particular display within a limited (but not fully predictable) area, as if a 3d texture were being rendered there.
The (apparent) texture, itself, always appears to consist of a jumbled mess of pixels sampled "accidentally" from somewhere in video/compositor memory (but not necessarily the pixels from the desktop effect).
While this happens, the "desktop effects" magic works fine, and nothing else wierd happens; it just goes away once I stop moving my window (or whatever).
Forgot to mention: I'm running the amdgpu driver.
I still see occasional flickering and corrupted squares on both me and my mother's computers, both running openSUSE Tumbleweed and AMD video cards but obviously different hardware. Even when changing video cards, the issue will more or less persist just happen at different stages. Sometimes it's just an annoyance that goes away quickly, at other times desktop effects or even the whole computer must be restarted because the graphical corruption covers the entire screen and you can't see anything any more. It also happens with both 'radeon' and 'amdgpu', the problem is not exclusive to any one driver.
This is clearly something deep in the core renderer code or AMD drivers which has been going on for a long time now. I'm pretty surprised it's not being discussed a lot more often, since from what I'm seeing it's something thousands of users should be able to easily confirm.
To be more clear about this, it's not the Radeon driver. It happens with Nvidia as well. This bug has existed for the better part of a decade, it's just that nobody cares to address it. There are even widgets written to toggle compositing off and back on to "fix" your desktop.
It presents in what appears to be several ways but in reality is very few; the gist of it is that screen updates simply stop happening for a large number of methods, they seem to get blocked on something. Screen updates will happen on significant context change. That is, changing virtual desktops, switching to text and back to gui, manual movement of windows, etc. All other triggered updates simply go to narnia.
Symptoms; screen appears to freeze, modal dialogs make screens flash, frozen tearing, very choppy scrolling in browser, etc.
You can restart your compositor by toggling it off and back on; shift-alt-f12 twice with default key bindings for KDE/plasma.
(In reply to David Ford from comment #11)
> To be more clear about this, it's not the Radeon driver. It happens with
> Nvidia as well.
So it's a kwin issue then, not a driver one?