Bug 512165

SUMMARY
After powering off my monitor to save some energy and later turning it on again fullscreen does not work anymore. The monitor tells me that it lost the connection to my computer. Inputs are still working fine. If i turn off fullscreen mode the connection to my monitor is restored and i can use the system normally, except entering fullscreen in any application.

STEPS TO REPRODUCE
1. Power off external monitor (So that no active monitor remains)
2. Enable monitor again
3. Enter fullscreen with any application (e.g. F11 in firefox)

OBSERVED RESULT
Monitor loses signal to system. System still works. Exiting fullscreen (e.g. pressing F11 in firefox again) restores connection to monitor. Problem remains until system is rebooted.

EXPECTED RESULT
Fullscreen works without problems.

SOFTWARE/OS VERSIONS
Operating System: NixOS 25.11
KDE Plasma Version: 6.5.2
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0
Kernel Version: 6.12.57 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5800X 8-Core Processor
Memory: 16 GiB of RAM (15,5 GiB usable)
Graphics Processor: NVIDIA GeForce RTX 3070 Ti
Manufacturer: Micro-Star International Co., Ltd.
Product Name: MS-7C91
System Version: 2.0

ADDITIONAL INFORMATION
My monitor is connected via DisplayPort to my dedicated Nvidia gpu. So it might be an nvidia issue. 

I shortly tested it with the nouveau drivers (instead of the proprietary drivers) where i could observe the same issue. But in this setup my session seemed to completley crash as i cloud not restore my visuals in any way.