Hello,

I use a Dell UP2414Q 24" 4K display. On Kubuntu 14.04 I was able to use the display in a normal way. Everything went fine out of the box.
Now I decided to use newer software and installed several linux distros including KDE. Everytime the screen was split into two equal parts with 1920x2160 DPI each.
There was DP1-8 and DP1-9.

Via settings I was unable to get a single screen with full resolution.

Is there a way to get this fixed?

___
Jens

Code: Select all

xrandr --output DP1-8 --auto --output DP1-9 --auto --right-of DP1-8


These are actually two outputs in one frame - seems kscreen thinks it's a good idea to clone ("unify") them by default, check "kcmshell5 kscreen" for the settings.

Output of "kcmshell5 kscreen"

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LOAD
kscreen: launcherDataAvailable: "org.kde.KScreen.Backend.XRandR"
kscreen: Launcher finished with exit code 1 , status 0
kscreen: Service for requested backend already running
kscreen: Primary output changed from KScreen::Output(Id: 68 , Name: "DP1-8" ) ( "DP1-8"
) to KScreen::Output(Id: 68 , Name: "DP1-8" ) ( "DP1-8" )
kscreen: Primary output changed from KScreen::Output(Id: 68 , Name: "DP1-8" ) ( "DP1-8"
) to KScreen::Output(Id: 68 , Name: "DP1-8" ) ( "DP1-8" )
Activate output 68
kscreen: Primary output changed from KScreen::Output(Id: 68 , Name: "DP1-8" ) ( "DP1-8" ) to KS
creen::Output(Id: 68 , Name: "DP1-8" ) ( "DP1-8" )

It's supposed to show a dialog (unless you have that already opened in systemsettings....)

luebking wrote:It's supposed to show a dialog

When opening the display settings, there are two different screens DP1-8 and DP1-9. If I unify them, I have one screen with 1920x2160 DPI resolution.

Yes, you shall *not* "unify" them (that means one screen clones the other), but put them next to each other.
Your monitor is actually two screens that were screwed into the same frame - not sure why the logic is exposed, but you simply want to configure one on the left and the other one on the right (thus the xrandr call)

luebking wrote:Yes, you shall *not* "unify" them (that means one screen clones the other), but put them next to each other.

That is the default.

After installation, I get two separate workspaces caused by two different displays recognized by the software.

What I'm looking for is a correct recognition of my display with a resolution of 3840x2160 pixels. If I'd decide to be in need of two workspaces, I could probably set this up via software.

I think we're talking past each other.
Plasmashell (the desktop process) does not support to span one desktop/panel across two screens (never did), but that's not related to the "workspace"

https://bugs.kde.org/show_bug.cgi?id=273269
https://bugs.kde.org/show_bug.cgi?id=167825

Afaiu, this was a fundamental decision, I'd not expect it to be ever fixed.
However you claimed it worked before, so the driver must have signalled a 3840x2160 from the screen before... (and you're looking for a lower level solution, it's not a KDE specific issue, right? Didn't get that.)

> What I'm looking for is a correct recognition of my display with a resolution of 3840x2160 pixels
The internet says you've to enable DP1.2 + MST in the display to have it report itself as one output (and also the GPU needs to support that), but you claimed "worked fine with 14.04" and didn't mention to have changed things reg. the Hardware?

Remainder could be the GPU driver - maybe used nvidia blob before and are now on nouveau?