Bug 501451

SUMMARY
The previous screen brightness is not restored when power is restored, after the laptop was in a low battery state

STEPS TO REPRODUCE
1. Scroll up over the Brightness and Color widget to set the screen brightness to 100%, if was not already there.
2. Disconnect the power cable or turn off the power outlet, if you have a button on it for that.
3. Wait until the battery is low and the screen brightness has been automatically set to 30%.
4. Connect the power cable or turn on the power out, if you did that instead.


OBSERVED RESULT
1. When battery gets into the 'low' state, the screen brightness goes from 100% to 30%.
2. When the power is back on, meaning that the power comes from the wire and not from battery, the brightness it doesn't go from 30% back to 100% where it was before the power was interrupted.
Restoring the power doesn't also restores the brightness.

EXPECTED RESULT
Restoring the power restores the previous screen brightness level.
In my case it was set to 100%, but if I was setting it to 90% or 80% while the power was connected, then after disconnect and restoring the power again, the screen brightness would be restored to 90% or 80% like before.
Manually setting the screen brightness to a specific value, it's exactly as explaining to the computer what it's my preference for the brightness.
The computer should not decide on it's own to change my preference.
It's understandable and accepted that it's automatically set to 30% when the battery is very low to keep it on as long as possible.
But it's not, that not everything is restored to their previous values when the power comes back again.

SOFTWARE/OS VERSIONS
Linux (Debian 13 - unstable repository)/KDE Plasma:
KDE Plasma Version: 6.3.2
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2
Kernel Version: 6.12.17-amd64 (64-bit)
Mesa  Version: 25.0.0-1
Graphics Platform: Wayland


HARDWARE SPECIFICATIONS
Hardware: Laptop Dell Inspiron 5770 (17" 1080p@60Hz screen)
CPU: Intel® Core™ i5-8250U CPU @ 1.60GHz
GPU 1: Intel® UHD Graphics 620 (main, Vulkan capable)
GPU 2: AMD Radeon R5 M465 Series
RAM: 8 GiB (7.7 GiB usable)


ADDITIONAL INFORMATION
BTW, my laptop also has a illuminated keyboard.
That could be turned off completely when the battery is low, but when the power comes back, I expect that the illumination level goes back to its previous level, like the screen brightness.
So, for both the screen and the keyboard, I expect that their manually set levels (by scrolling over the widgets or by dragging the sliders inside) are restored when the power comes back.
If other changes were made that I'm not aware now, while the battery was low, I expect that those too come back to their previous levels.
BTW, my laptop has a loose power connector and it disconnects a lot while in bet and it's very annoying to have to manually fix the screen brightness too after I plug the power connector back in.