Bug 484592

Summary:	External display rendered unusable due to misconfiguration
Product:	[Plasma] KScreen	Reporter:	Matthias <shalokshalom>
Component:	common	Assignee:	kscreen-bugs-null <kscreen-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	major	CC:	fanzhuyifan, nate
Priority:	NOR	Keywords:	multiscreen
Version First Reported In:	6.0.2
Target Milestone:	---
Platform:	Other
OS:	Linux
See Also:	https://bugs.kde.org/show_bug.cgi?id=485285
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Matthias 2024-03-27 11:50:28 UTC

SUMMARY

I managed to setup the external TV in a way, that it is completely unusable from this installation. 
There is currently no GUI way, to restore its functionality as external display. 
I suggest to implement a functionality, that allows to configure previous output devices even when they are not connected. (Or at least restore their settings)


STEPS TO REPRODUCE
1. Connect an external display
2. Choose an incompatible resolution (2560x1440)
3. Switch to it as the only output source (Fn+F7 in my case)

I also set the TV as the primary display in the KCM, idk if thats important to replicate. 

OBSERVED RESULT

Both devices stay black, once the TV is connected.

EXPECTED RESULT

Either the OS recognizing and accommodating for the issue, or providing an option to reset the ill setting manually before the connection happens. ab 

Operating System: NixOS 24.05
KDE Plasma Version: 6.0.2
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.2
Kernel Version: 6.6.22 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5800U with Radeon Graphics
Memory: 13,5 GiB of RAM
Graphics Processor: AMD Radeon Graphics

ADDITIONAL INFORMATION

I like to add, that the chosen resolution is not only made available by the KCM, it is also a theoretically compatible format (16:9 on this LG E9)

So this can happen easily to common users. 

I actually replicated that based on an issue, 
that a friend of mine just experienced on Windows. 

Seems like we can do better here ;)

Comment 1 Matthias 2024-03-27 12:10:10 UTC

Maybe we add kscreen-doctor to the KCM? (By the way, there is no component for KScreen here in the bugtracker)

Comment 2 fanzhuyifan 2024-03-27 15:57:26 UTC

The configuration should automatically revert after 15 seconds if you don't hit confirm. Is this what you are looking for?

Comment 3 Matthias 2024-03-28 07:05:56 UTC

No. I missed to specify that, but the error occurs, when I confirm a configuration, that doesnt work.

As you can read from my report, I am already in a situation, that prevents me from using that TV as an external display.

There is no way, to restore its functionality so far as I can see. (Not even modifiying a text file can help, sincs that one is generated and cannot be modified seemingly.)

The issue is, that the irrevertable action does not come with the KCM setting itself, but by using the Fn+F7 menu (dont know its name) with which you determine the output configuration.

It allows you to choose between several options, among those: 

) Switch to internal display 
) Switch to external display
) Unify output
) Extend left
) Extend right

If you choose to follow the steps outlined in the original report, and then choose 'Switch to external display' there is no way of changing the setup again. 

And plugging the device in, will always result in a black screen on both devices. 

Since it is only possible to edit it once plugged in, and plugging it in, it switches to 'external screen only' - even though that one is in an ill state. 

The TV rejects the format, and we seem to have no detection for that.

Another possible solution would be, to never except such an illegal state in the first place. 

My TV does not accept a seemingly plausible resolution (2560 x 1440) and shows this on its screen.

I dont know, if it reports this back on an API as well.

Comment 4 Matthias 2024-04-09 21:58:40 UTC


*** This bug has been marked as a duplicate of bug 485285 ***

Comment 5 Matthias 2025-10-06 12:04:42 UTC

I just ran into this again (the confirmation window did not revert to the working state, for some reason) on Arch Linux.