https://bugs.kde.org/show_bug.cgi?id=524470
Bug ID: 524470
Summary: Brief whole-screen brightness/contrast flicker on
internal eDP display in Plasma Wayland on Intel UHD
620
Classification: Plasma
Product: kwin
Version First unspecified
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: platform-drm
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: ---
Created attachment 195285
--> https://bugs.kde.org/attachment.cgi?id=195285&action=edit
kscreen-output
SUMMARY
On Plasma Wayland, the built-in eDP display briefly changes brightness/contrast
for a fraction of a second when screen content changes.
For example, hovering over a UI element that causes it to highlight can
sometimes
cause the rest of the screen to very subtly darken/change contrast for a
fraction
of a second, then immediately return to normal.
The effect is subtle and intermittent, but visible during normal desktop use.
The problem does NOT occur in a Plasma X11 session on the same Fedora
installation.
It also did not occur when running Ubuntu or Linux Mint on the same
laptop/display.
STEPS TO REPRODUCE
1. Log into Plasma Wayland.
2. Use the built-in laptop display.
3. Interact with UI elements that cause small areas of the screen to change
color,
such as hovering over buttons/menu entries/highlights.
4. Occasionally the overall background/display very briefly appears to dim or
change contrast, then returns to normal.
The issue is intermittent and can be difficult to deliberately reproduce.
OBSERVED RESULT
The internal laptop display occasionally undergoes a very brief, subtle
whole-screen brightness/contrast change when displayed content changes.
EXPECTED RESULT
Changing or highlighting a small UI element should not affect the brightness or
contrast of the rest of the display.
SYSTEM INFORMATION
Operating System: Fedora Linux 44
KDE Plasma Version: 6.7.4
Graphics Platform: Wayland
Laptop: Lenovo ThinkPad T480s
GPU:
Intel Corporation Kaby Lake-R GT2 [UHD Graphics 620]
Kernel driver: i915
Internal display:
eDP-1
1920x1080 @ 60.01 Hz
The internal display reports:
- VRR: incapable
- HDR: incapable
- Wide Color Gamut: incapable
- ICC profile: none
- Automatic brightness: unsupported
- Adaptive backlight modulation: unsupported
- PSR: unsupported by panel
TESTING / TROUBLESHOOTING ALREADY PERFORMED
- The problem occurs while plugged into AC power.
- An external display does NOT exhibit the problem.
- Panel Self Refresh was checked through i915 debugfs:
"Sink support: PSR = no"
- Changing display scaling from 110% to 100% does NOT fix it.
- Forcing output color resolution from automatic/10 bpc to 8 bpc does NOT fix
it.
- There is no ICC profile configured.
- VRR, HDR and WCG are unsupported by this panel.
- Ubuntu and Linux Mint do NOT exhibit the problem on the same laptop/display.
- Plasma X11 on the SAME Fedora 44 installation does NOT exhibit the problem.
Therefore the problem appears specific to the Plasma Wayland display path on
this hardware rather than the physical LCD itself.
The effect is extremely brief and subtle, so reliably capturing it in a
screenshot
is not practical.
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