https://bugs.kde.org/show_bug.cgi?id=518040
Bug ID: 518040
Summary: Brightness capped after resuming from
suspend/unplugging external monitor
Classification: Plasma
Product: kwin
Version First unspecified
Reported In:
Platform: openSUSE
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
Not sure this is really a KWin bug, but I'm pretty sure it is a Plasma bug.
I work with a laptop connected to an external monitor. The external monitor is
set up to extend the laptop's screen on the left. Sometimes, after I resume the
laptop from suspend (the laptop always stays plugged into the monitor), the
laptop's screen brightness is noticeably reduced (around half of what it was
before suspending), even though KDE shows that the laptop's screen brightness
value is unchanged. Basically, the 100% brightness value now corresponds to a
backlight intensity that is only around half of the real maximum, and all lower
values are reduced as a consequence too. Adjusting the brightness using the
brightness applet or the hardware keys works, but as I've said, the available
adjustment range seems to be [0, <incorrect, dim max value reported as 100>]
instead of the correct, expected, "true" [0, 100] range supported by the
hardware.
Sometimes, the same happens if I unplug and replug the external monitor.
When this happens, the only way to fix the issue is to reboot the computer. I
am unsure if logging out and then back in is enough, as I have never tried
doing so yet.
The external monitor's brightness is never affected by this issue.
To me, this seems an instance of the problem described by Reddit user jpetso
here:
https://www.reddit.com/r/kde/comments/1g3wzka/plasma_62_display_brightness_incorrect_after/
Which in turn seems to be possibly related to this issue:
https://bugs.kde.org/show_bug.cgi?id=482713
STEPS TO REPRODUCE
1. Use a laptop connected to an external monitor. Set the laptop's brightness
to 100%.
2. Suspend and resume the laptop, or unplug and replug the monitor (neither
trigger is reliable, the issue only arises sometimes)
3. Observe that KDE still reports the brightness to be 100%, but the laptop
screen is noticeably dimmer.
OBSERVED RESULT
The brightness of the laptop's display is reduced, e.g. the maximum value is
much dimmer than it should.
EXPECTED RESULT
The laptop's display brightness works as it should.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: openSUSE Tumbleweed
KDE Plasma Version: 6.6.2
KDE Frameworks Version: 6.24.0
Qt Version: 6.10.2
ADDITIONAL INFORMATION
Please let me know if I can further help you debug or test possible fixes for
this issue.
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