Bug 503639

Summary:	Display dimming is able to affect a monitor when the monitor is not focused on said input
Product:	[Plasma] plasmashell	Reporter:	Antti Savolainen <antti.savo>
Component:	Power management & brightness	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	CONFIRMED ---
Severity:	minor	CC:	bshah, nate
Priority:	NOR	Keywords:	multiscreen
Version First Reported In:	6.3.4
Target Milestone:	1.0
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Displays

Description Antti Savolainen 2025-05-02 02:40:31 UTC

SUMMARY
If you have 2 computers plugged to the same monitor and the computer currently not being displayed dimms the display due to lack of activity, it dimms the display for the computer that is on the monitor. Not sure if there is a way to detect a computer not having its input tuned in, but I'll report this anyways. 

STEPS TO REPRODUCE
1. Plug 2 computers to the same monitor
2. Do something on one while letting the other go idle

OBSERVED RESULT
Display gets dimmed even if you're doing something

EXPECTED RESULT
The computer not on front should detect that it is not and refrain from dimming when it knows it will interfere with the other computer

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.13.0
Qt Version: 6.9.0
Kernel Version: 6.14.4-arch1-2 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 2600 Six-Core Processor
Memory: 62.7 GiB of RAM
Graphics Processor: AMD Radeon RX 5700

Comment 1 Bhushan Shah 2025-05-07 11:17:33 UTC

I can confirm this bug, although it seems to happen only one monitor of mine and not on other.

Can you me which monitor you have?

Comment 2 Antti Savolainen 2025-05-07 17:09:42 UTC

Created attachment 181035 [details]
Displays

Asus MG279 and Samsung C27JG5x. I guess some monitors have protections against changing the bringtness from sources that are not allowed.

There isn't a need to wait for the computer to dim the screen. Just tweaking the brightness settings is enough.