Bug 498277

Summary:	Power Management KCM "Change screen brightness" settings never take effect
Product:	[Plasma] plasmashell	Reporter:	Oded Arbel <oded>
Component:	Power management & brightness	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	normal	CC:	john.kizer, jpetso, nate
Priority:	NOR
Version First Reported In:	master
Target Milestone:	1.0
Platform:	Neon
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Oded Arbel 2025-01-05 10:40:39 UTC

SUMMARY
On Plasma 6.2, setting the "Change screen brightness" slider to any value, on any power state - does not appear to have any effect on the system at any point.

STEPS TO REPRODUCE
1. Make sure the laptop is connected to AC power.
2. Open Power Management KCM
3. Under "On AC Power" check the "Change screen brightness" checkbox and set the slider to some value (lets say - 75%").
4. Under "On Battery" check the "Change screen brightness" checkbox and set the slider to some other value (lets say - 50%).
5. Unplug the AC power cable.
6. Re-plug the AC power cable.

OBSERVED RESULT
The laptop screen brightness does not change.

EXPECTED RESULT
The laptop screen brightness should change to 50% when power is disconnected, and then change to 75% when the power is reconnected (I think, regardless of what the brightness was set to before).

SOFTWARE/OS VERSIONS
Operating System: KDE neon Testing Edition
KDE Plasma Version: 6.2.5
KDE Frameworks Version: 6.10.0
Qt Version: 6.8.1
Kernel Version: 6.8.0-51-generic (64-bit)
Graphics Platform: Wayland
Processors: 20 × 12th Gen Intel® Core™ i7-12700H
Memory: 31.0 GiB of RAM
Graphics Processor: Mesa Intel® Graphics

ADDITIONAL INFORMATION
It appears that all of the other "Display and Brightness" toggles in the Power Management KCM do not function either: setting "Dim automatically" doesn't dim the screen after the specified time, no "Turn off screen". I haven't played with "Change keyboard brightness" yet, so can't verify if that works.

Comment 1 Nate Graham 2025-01-06 19:17:45 UTC

This could be a kernel or upower bug.

Comment 2 Oded Arbel 2025-01-07 12:55:07 UTC

I think there may have been a misunderstanding:

1. I understand "RESOLVED INTENTIONAL" to mean that the behavior described is "as intended" - which I don't understand how can that be the case: are you saying that having a bunch of UI that does nothing is intentional?
2. The comment makes more sense - is this an issue with another software lower down the stack (in which case "RESOLVED UPSTERAM" or "RESOLVED NOTABUG") may have been more suitable.

Regarding the actual content of the comment:

To my understanding this is not an issue with either the ability of powerdevil to control brightness (the brightness control widget works fine, as well as keyboard shortcut binding and the D-Bus API), nor with the ability of powerdevil to detect the power state:

```
$ qdbus org.kde.Solid.PowerManagement /org/kde/Solid/PowerManagement org.kde.Solid.PowerManagement.currentProfile
AC
...
$ qdbus org.kde.Solid.PowerManagement /org/kde/Solid/PowerManagement org.kde.Solid.PowerManagement.currentProfile
Battery
```

So it doesn't seem like lack of information that is needed for PowerDevil to perform actions, nor lack of ability to perform actions - it seems that PowerDevil just fails to perform actions it promised to take, that it can take, on the basis of information that it has.

Comment 3 Nate Graham 2025-01-07 16:47:45 UTC

Oops, I didn't actually intent to close this, sorry.

Comment 4 John Kizer 2025-01-13 19:30:43 UTC

Hi - merging this in with the existing issue report where this one is being tracked. Thanks!

*** This bug has been marked as a duplicate of bug 494956 ***