https://bugs.kde.org/show_bug.cgi?id=524915
Bug ID: 524915
Summary: Brightness tray applet slider stops updating after
manual drag; ignores later Fn-key/auto-dim brightness
changes (actual brightness and tooltip stay correct)
Classification: Plasma
Product: plasmashell
Version First 6.7.4
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Brightness and Color widget
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: 1.0
Created attachment 195586
--> https://bugs.kde.org/attachment.cgi?id=195586&action=edit
screenshot
DESCRIPTION
The brightness slider in the "Brightness and Color" system tray applet stops
reflecting the actual screen brightness after it has been manually dragged
once. Afterwards it no longer updates when the brightness is changed externally
(Fn keys, or PowerDevil's automatic dimming on low battery), even though the
actual screen brightness does change correctly and the tray icon's hover
tooltip shows the correct value.
STEPS TO REPRODUCE
1. Log in / restart Plasmashell so the system tray is freshly loaded.
2. Open the "Brightness and Color" system tray popup and drag the brightness
slider with the mouse at least once (e.g. to 100%).
3. Close the popup.
4. Change the brightness using a different method, e.g. the keyboard Fn
brightness keys, or let PowerDevil dim the screen automatically (e.g. via the
"dim screen at X% battery" setting).
5. Open the "Brightness and Color" system tray popup again.
OBSERVED RESULT
The slider still shows the value from step 2 (e.g. 100%), not the actual
current brightness. The real screen brightness has changed correctly (confirmed
visually and via the Fn-key OSD, which does show the correct value). Closing
and reopening the popup again does not fix the display — the slider stays stuck
at the stale value.
Only fully restarting Plasmashell (`plasmashell --replace`) makes the slider
show the correct value again — until it is manually dragged once, after which
the same desync reoccurs.
Additionally, the following error is printed to the console every time the
brightness tray icon is clicked (not for other tray icons), while the slider is
in this desynced state:
`qrc:/qt/qml/plasma/applet/org/kde/plasma/systemtray/ExpandedRepresentation.qml:239:
TypeError: Cannot read property 'text' of null`
EXPECTED RESULT
The brightness slider should always reflect the actual current screen
brightness, whether it changed via the slider itself, the Fn keys, or
PowerDevil's automatic dimming — both live while the popup is open and freshly
on every popup open.
SOFTWARE/OS VERSIONS
Operating System: CachyOS (Arch-based)
KDE Plasma Version: 6.7.4
KWin/Session: Wayland
Kernel: Linux 7.2.0-1-cachyos
Qt Version: (please fill in via `plasmashell --version` / `kf6-config
--version` if you want to add it before submitting)
ADDITIONAL INFORMATION
- Hardware: Lenovo ThinkPad E14 Gen 3 (20Y700AJGE), AMD Ryzen 5 5500U, AMD
Radeon (Lucienne, integrated GPU), internal 1920x1080 14" 60Hz display.
- The Fn-key OSD popup (the separate overlay shown centered above the taskbar)
always updates correctly and is not affected by this bug — only the persistent
slider inside the system tray "Brightness and Color" popup is affected.
- The tray icon's own hover tooltip (mouse-over without clicking) also always
shows the correct current brightness — only the expanded popup's slider value
is stale.
- This appears to be an initialization/binding issue: the slider seems to read
the real brightness value only once when the widget/plasmashell is loaded, and
once the user interacts with the slider directly, it appears to stop reflecting
external changes altogether (possibly a broken QML property binding that gets
replaced by a static value on user interaction).
- Not tested yet: whether this also occurs on X11, since I only use Wayland.
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