Bug 484944

Summary:	Wayland session disables internal monitor
Product:	[Plasma] kwin	Reporter:	Michael Magyar <michael.magyar>
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED NOT A BUG
Severity:	major	Keywords:	multiscreen, wayland-only
Priority:	NOR
Version First Reported In:	6.0.3
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	kwinoutputconfig.json from my system

Description Michael Magyar 2024-04-02 20:01:38 UTC

Created attachment 168069 [details]
kwinoutputconfig.json from my system

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SUMMARY
After configuring an external monitor using the wayland session the laptop's built in monitor seems to be stuck in a disabled mode. After disconnecting the external display the internal remains a black screen. Even after a power cycle the wayland session continues to have a black screen on the laptop's internal monitor.

Switching to an X11 session the internal display works correctly. I have attempted to remove the generated kscreen files as suggested by https://bugs.kde.org/show_bug.cgi?id=410674, and removing kwinoutputconfig.json in an attempt to have the file regenerated.

Creating a new user and logging in using that user with a Wayland session the internal display works correctly.

STEPS TO REPRODUCE
1. Connect laptop to external display
2. Attempt to configure screen mirroring
3. 

OBSERVED RESULT
External display works as expected, but internal is blank.

EXPECTED RESULT
Both internal and external displays should show the desktop, either mirrored or as an extended desktop.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 6.0.3
KDE Frameworks Version:  6.0.0
Qt Version: 6.6.3

ADDITIONAL INFORMATION
System is using AMD Ryzen 7 PRO 7840U w/ Radeon 780M Graphics

Comment 1 Michael Magyar 2024-04-08 17:16:49 UTC

Hello,

Poking around I have figured out this situation. I believe this may just be a quirk of the Thinkpad P14s Gen4 AMD ( 21K5001JUS ). At some point the resolution settings for the internal display changed from the display's 16:10 aspect ratio to a 16:9 aspect ratio with the same scaling factor. These settings result in the display remaining blank. I would guess I changed this when connecting to a 16:9 external display in mirroring mode. 

Changing the internal display back to a 16:10 aspect ratio output gets all my displays working correctly again.