Bug 488111

Created attachment 170204 [details]
Broken kwinoutputconfig.json

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SUMMARY
Selecting "unify outputs" when connecting an external screen to my laptop permanently disables the laptop screen, pretty much bricking the system.

STEPS TO REPRODUCE
1. Connect an external screen to a laptop
2. Select "unify outputs"

OBSERVED RESULT
1. The internal laptop screen goes black.
2. After disconnecting the screen, the screen stays black.
3. After hard-reset, the login screen shows up, but after sign in, it goes black again.
4. Under a different user, the screen works normally.

EXPECTED RESULT
"Unify output" actually unifies output. Both screens work, and after disconnection the internal laptop screen keeps working as usual.

HOW TO RECOVER
1. Find an external screen that works.
2. Create another user.
3. Sign into that user (the internal screen should work normally).
4. Remove .config/kwinoutputconfig.json from your main user home directory.

Note that it is necessary to go through that another user because if you delete the file directly, KDE will simply recreate it with the same content.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora Linux 40
KDE Plasma Version:  6.0.5
KDE Frameworks Version: 6.2.0
Qt Version: 6.7.1

Using Wayland on Lenovo Thinkpad T14s with AMD Ryzen 7 PRO 7840U.

ADDITIONAL INFORMATION

This is very annoying problem because it pretty much bricks the system.

Not sure how I reproducible this is but in my current setup (the aforementioned laptop + a ThinkVision external screen connected via USB-C) I managed to reproduce it immediately on a new account.

I'm attaching kwinoutputconfig.json causing the issue.