Bug 506122

Summary:	Brightness of unused screens is changed to 100% even when configured to a different value
Product:	[Plasma] plasmashell	Reporter:	Juraj <jurajoravec>
Component:	Power management & brightness	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal	CC:	kdedev, nate
Priority:	NOR	Keywords:	multiscreen
Version First Reported In:	6.3.5
Target Milestone:	1.0
Platform:	Other
OS:	Linux
See Also:	https://bugs.kde.org/show_bug.cgi?id=500799
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	kscreen-doctor

Description Juraj 2025-06-24 17:57:29 UTC

SUMMARY
When having multiple monitors connected to the main machine (with plasma/wayland) and some monitors are displaying stuff from other machines.
Plasma wants to set the briughtness of the connected monitors inactive in plasma but used by other devices to 100% even when the given monitor is configured to be at 30% brightnes.

STEPS TO REPRODUCE
1. Have 2 monitors, both connected to plasma machine and one to external machine
2. Have only one monitor enabled is plasma settings, and have the other be used by other machine
2. start the system / login

OBSERVED RESULT
Brightness of the plasma inactive monitor but used by other machine is set to 100%

EXPECTED RESULT
The brightness of NOT enabled monitor is left untouched.

SOFTWARE/OS VERSIONS
Operating System: Artix Linux 
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0
Graphics Platform: Wayland

ADDITIONAL INFORMATION
There is a possibly relevant bug: https://bugs.kde.org/show_bug.cgi?id=494497
I do not know if this is exactly same use case, so feel free to close this one if they are the same.

Comment 1 TraceyC 2025-06-26 00:57:20 UTC

I tested this on git-master and cannot reproduce

Laptop 3840 x 2400 @ 150%, connected to a dock
2 external monitors 3440 x 1440 @100 %

Second external monitor was set to 50% brightness.
Disabled it
Started up another machine which output display to that monitor
Checked the brightness settings on the git-master system - brightness was still at 50%

Can you please copy and paste the output of this into the report? Thanks.

kscreen-doctor -o

Comment 2 Juraj 2025-06-26 07:55:47 UTC

Created attachment 182680 [details]
kscreen-doctor

In power management settings I also have set:
Dim after: 10 mins. (The screen will not be dimmed because it is configured to turn off sooner.)
Turn off after: 10 mins.

> Brightness control: supported, set to 21% and dimming to 100%
How to change the dimmed brightness?

Comment 3 TraceyC 2025-06-26 17:22:49 UTC

Thanks for the additional information.

(In reply to Juraj from comment #2)
> > Brightness control: supported, set to 21% and dimming to 100%
> How to change the dimmed brightness?

There is not a way to change that percentage, which is for dimming, not the dimmed brightness.
It always shows 100% that I've seen, and currently does on my system.

This is possibly related to bug 500799

I'll let the kwin developers take it from here.

Comment 4 TraceyC 2025-07-23 14:55:52 UTC

The reporter in bug 500799 has reported that after switching to Tuxedo OS, the problem is no longer occurring on their system. Are you still seeing this bug with Plasma 6.4.3 and ddcutil 2.2.1? If so, please set this back to REPORTED. Thanks!

Comment 5 Bug Janitor Service 2025-08-07 03:46:39 UTC

🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!

Comment 6 Bug Janitor Service 2025-08-22 03:47:19 UTC

🐛🧹 This bug has been in NEEDSINFO status with no change for at least 30 days. Closing as RESOLVED WORKSFORME.