Bug 494588

SUMMARY
Monitor screen brightness is reduced after monitors are automatically turned off and on. This is with a dual-monitor setup (unsure if relevant).

STEPS TO REPRODUCE
1. enable "Turn off screen" setting, set screen brightness to 100%
2. wait for monitors to turn off
3. use mouse/keyboards to re-enable the monitors

OBSERVED RESULT
The monitor brightness is set to 30% instead of 100%. The new brightness is always 30%, but it is unclear where the 30% value is coming from - I do not have the "Dim" option set, and there's no 30% in any related config tool that I can find.

Of note is that sometimes only one monitor is set to 30%, and sometimes both are. If I turn a monitor off+on manually, the brightness change is not observed (in limited testing).

EXPECTED RESULT
Monitors set to 100%.

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20241007
KDE Plasma Version: 6.2.0
KDE Frameworks Version: 6.6.0
Qt Version: 6.7.3
Kernel Version: 6.11.2-1-default (64-bit)
Graphics Platform: Wayland
Processors: 4 × AMD Ryzen 3 3200G with Radeon Vega Graphics
Memory: 29.3 GiB of RAM
Graphics Processor: AMD Radeon Vega 8 Graphics

In a similar report, it was noted that the ~/.config/kwinoutputconfig.json file may change when this happens, and indeed it does, here's the diff:

6c6
<                 "brightness": 0.3,
---
>                 "brightness": 1,
29c29
<                 "brightness": 0.3,
---
>                 "brightness": 1,