Wayland rest external screen brightness

Hey - experiencing something extremely weird behaviour using KDE Wayland

After logging in - during the splash screen KDE will always set the screen to a certain brightness.

I’ve noticed today that my external monitor being extremely dim after restarting the computer without apparent reason…

After testing this also happens anytime a monitor gets connected

Here’s the setup -
HP Omen 17 Laptop, Intel CPU + Nvidia GPU
KDE Wayland
Arch Linux (EndevourOS)
LG 45GR95QE Monitor, connected via DP

at first its setting it to 9% brightness each time i login into a session, to diagnose i’ve tried a few things but to no apparent avail, but here’s what i’ve found

  • this does not happen under x11 (Tested GNOME, Budgie, KDE, Cinnimon) , the screen brightness remains unchanged
  • this does not happen under GNOME Wayland
  • Always happens under KDE Wayland. I’ve went as far as reinstall the entire system (and accidentally lost some data… should have been more careful on the backup). Before the reinstall its setting it to 9% but after reinstallation its setting it to 100%, which is blinding my eye :joy:
  • I am able to set the monitor bright using ddcui, but it always get overwritten the next time i login, which does raise some concern that if each time that i login some data get written into the monitor’s memory, this could potentially wear the memory out a lot faster than we anticipated
  • all powerdevil brightness auto adjustment was disabled - while they do work on my laptop’s built in display, it doesn’t work on external monitor anyway
  • tried to mask systemd-backlight, nothing happens
  • tried different cable, external setup, nothing changed

I’ve tested another machine (desktop setup this time) - its the same behavior, that the screen get set to 100% brightness

Setup - 5800x, 32GB RAM with Arc A770, Mesa Driver

and turns out its even worse - its either when i login, or when i switch the monitor from one device to another the brightness got reset to 100%

This does not happen during the login screen or if i use x11 session

Pretty sure this is a bug, not too sure which components though

not too sure whats going on… i am stuck under x11 at the moment and there are a few applications that i really wants to use on wayland as its way smoother

potentially related to thread - Powerdevil is (re)setting my display brightness after the display wakes up

Hello,

I have a similar issue, detailed here: https://discuss.kde.org/t/powerdevil-is-re-setting-my-display-brightness-after-the-display-wakes-up/23079/17.

For me the solution was to use the new Brightness slider in Brightness and Color applet in panel, and set the brightness to the value that I had earlier (before this new feature reset it). This persisted reboots and resolved the issue.

Though X11 is the simplest workaround, for someone using Wayland we still would like it to be fixed.

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