Weird Plasma display issue - AMD GPU

For the past few updates I have had this weird issue with my main display not…displayed correctly. Here is a picture I took:

As you can see, it’s like it is bleeding over into my secondary display. This is the currently resolution and orientation set:

I am currently running KDE Plasma 40. My GPU is this (from lshw):

  *-display                 
       description: VGA compatible controller
       product: Navi 21 [Radeon RX 6800/6800 XT / 6900 XT]
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       physical id: 0
       bus info: pci@0000:03:00.0
       version: c3
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
       configuration: driver=amdgpu latency=0
       resources: iomemory:f80-f7f iomemory:fc0-fbf irq:105 memory:f800000000-fbffffffff memory:fc00000000-fc0fffffff ioport:f000(size=256) memory:f6a00000-f6afffff memory:f6b00000-f6b1ffff
  *-display
       description: VGA compatible controller
       product: Raphael
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       physical id: 0
       bus info: pci@0000:13:00.0
       version: c5
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi msix vga_controller bus_master cap_list
       configuration: driver=amdgpu latency=0
       resources: iomemory:fc0-fbf iomemory:fc0-fbf irq:66 memory:fc20000000-fc2fffffff memory:fc30000000-fc301fffff ioport:e000(size=256) memory:f6500000-f657ffff

The second is an onboard video card.
To me, and I could be wrong, it looks as if a plasmashell is confused being that there are two GPUs. I can log out and log back in and it will correct itself. However, I may have to repeat that several times before it does correct itself.
Anyone have any idea the issue and how to fix it?
Thanks in advance.

From the screenshot, the displays are arranged on top of each other, that is: both display areas form an area.

From the photo, whatever displays the purple part is a window which is taller than 1080px (probably 1440px) and - consequently - extends into the lower part.

How does this look if you arrange them differently, for example next to each other, or with a “gap”? Note that a gap may keep the mouse from moving between displays, unless you use a key for switching or such.

That display arrangement from the second screenshot represents how I want to navigate. When I move my mouse from the main display at the bottom to the top, I want the mouse to move to the display above. That is the way it has always worked. That is the way it is supposed to work. And, will work if I log out and log back in.

@mjg is suggestion you change the arrangement as an experiment to get an understanding of the issue, not as a solution.

Yes, experimental approach :slight_smile:

Also, I wasn’t sure whether @t3kg33k is aware of the effect of “oversize” windows protruding into a different display. If that’s all that is at works here (which could be proven by this experiment), then the only problem is that “that window” picks up the wrong height; in this case there is no “display glitch” here.

Understood. I will try that experiment when I get home after work and report back.

Added amdgpu, kde-plasma, multiple-displays

So, changing the arrangement fixed the issue.

What does this tell us, then? What is the root cause? That this is a driver issue?
How would I correct this permanently so that the Dell device is on the bottom and work correctly?

FOLLOW UP: After applying the change and going back in later to test moving back to the original arrangement with the Dell display on the bottom and the Ancor on the top, all is well. It has righted itself, somehow. This seems to be a “band-aid” fix without a root cause yet.

It tells us that it’s most probably not a driver issue.
I stlll don’t know what that purple window is, but the app which it belongs to seemed to get the height from the wrong display.

Indeed: Between the fist screenshot and the latest, you seem to have changed the “primary” display setting. It’s quite likely that that app took the height of the primary display (or asked Gnome in a way which gives the primary’s height).

The purple is just one of the random Halloween wallpapers selected. Within KDE, for each monitor, I have selected Wallpaper settings as type Slideshow and it is picking Halloween images from a folder.
It is my belief that this is not the root cause. But, related to something within KDE (plasmashell?) that is not arranging the displays correctly.
Is this something that maybe I should be reporting to KDE somehow? Should I post this issue on their forum?

So, I am still having this issue. And, my temporary “band-aid” doesn’t always work.
Any thoughts or suggestions on how I can permanently fix this issue?

UPDATE: I would like to report that I tried logging in using Wayland (not my preference as it seems wonky to me) and I no longer have the issue.
So, it would seem this may be a Plasma X11 issue? Which, to me, doesn’t seem like it would be an X11 issue. I don’t know. I’m floundering here. As stated before, this is a new, problem as of the past few months.