Bug 511196

Summary:	Monitors without a Wayland window do not transition to Night light without screen updates
Product:	[Plasma] kwin	Reporter:	anthonyjbarricelli
Component:	night color	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	nate, xaver.hugl
Priority:	NOR
Version First Reported In:	6.5.0
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Had to be on phone as BLF isn't captured through software. Notice how transition works when Konsole moves to other monitor

Description anthonyjbarricelli 2025-10-27 05:34:56 UTC

SUMMARY
*See video to understand what is happening*
Monitors without any Wayland windows do not slowly transition to night mode/blue light filter unless updates occur to the screen, e.g. a timer incrementing 1 second would cause the blue light filter to resync with other monitors each second.

If there is a Wayland window, the screen adjusts as expected (shown in video). This bug does not care for X11 windows like Discord.

The bug creates jarring transitions as the blue light filter eases in on some monitors, but not others.

STEPS TO REPRODUCE
1. Have multiple monitors connected (I have 4 total)
2. Have no or only X11 windows on one monitor
3. Set the night light/blue light filter with a timed transition (30 min)
4. Click the toggle from the bottom task bar tray
5. Observe as the blank monitor doesn't transition
6. Cause an "update"/redraw to the monitor, like moving the mouse to it and observe the "catch up" jolt to the correct color

OBSERVED RESULT
The monitors do not sync the blue light filter transition

EXPECTED RESULT
The monitors should be synced as they slowly transition to full blue light filter value

SOFTWARE/OS VERSIONS

Operating System: Arch Linux
KDE Plasma Version: 6.5.0
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0
Kernel Version: 6.17.5-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 9800X3D 8-Core Processor
Memory: 64 GiB of RAM (60.5 GiB usable)
Graphics Processor 1: NVIDIA GeForce RTX 5090/PCIe/SSE2
Graphics Processor 2: NVIDIA GeForce RTX 5090/PCIe/SSE2

ADDITIONAL INFORMATION
Also the cursor doesn't update its color until it changes form (e.g. cursor to window resizer), however this was noticed in 6.4.5. You can see it in the video as well

Comment 1 anthonyjbarricelli 2025-10-27 05:40:42 UTC

Created attachment 186216 [details]
Had to be on phone as BLF isn't captured through software. Notice how transition works when Konsole moves to other monitor

Comment 2 Zamundaaa 2026-01-22 14:23:30 UTC

I can't reproduce that in git master, so it's probably fixed in Plasma 6.6. There was code to schedule repaints on all screens for quite a while though... so if you can still trigger the issue in 6.6, just reopen this.

Comment 3 anthonyjbarricelli 2026-01-23 00:04:01 UTC

(In reply to Zamundaaa from comment #2)
> I can't reproduce that in git master, so it's probably fixed in Plasma 6.6.
> There was code to schedule repaints on all screens for quite a while
> though... so if you can still trigger the issue in 6.6, just reopen this.

I cannot recreate this either. Can turn this feature back on now :) thank you!