Bug 500683 - Filenames on specific desktop columns blurry with fractional scaling, depending on alignment settings
Summary: Filenames on specific desktop columns blurry with fractional scaling, dependi...
Status: CONFIRMED
Alias: None
Product: plasmashell
Classification: Plasma
Component: Desktop icons & Folder View widget (other bugs)
Version First Reported In: 6.3.1
Platform: Fedora RPMs Linux
: NOR minor
Target Milestone: 1.0
Assignee: Plasma Bugs List
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-02-24 17:49 UTC by madness742
Modified: 2025-09-13 17:56 UTC (History)
5 users (show)

See Also:
Latest Commit:
Version Fixed In:
Sentry Crash Report:


Attachments
Aligned desktop left to right, positioned in the upper left corner. (11.19 KB, image/png)
2025-02-24 17:49 UTC, madness742
Details
Aligned desktop right to left, positioned in the upper left corner. (11.04 KB, image/png)
2025-02-24 17:49 UTC, madness742
Details
Behaviour on 6.4.4. (16.38 KB, image/png)
2025-08-17 10:54 UTC, madness742
Details
Behaviour on 6.4.4 (increased font size). (20.60 KB, image/png)
2025-08-17 10:54 UTC, madness742
Details

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Description madness742 2025-02-24 17:49:13 UTC
Created attachment 178830 [details]
Aligned desktop left to right, positioned in the upper left corner.

SUMMARY
When using fractional monitor scaling, the left row of the desktop, will have a slightly blurry/fuzzy text. 

The affected row also changes depending on the alignment of the desktop icons. Aligning desktop icons to the right, and placing them back at the upper left corner will cause the second row to be blurry. It's also slightly misaligned. I took two screenshots with the "Remember Selected Area" feature of spectacles, but it might be difficult to see on the screenshots due to Bug 487997.

STEPS TO REPRODUCE
1. Set primary monitor to 125% scaling (2560x1440). 
2. Confirm the icons are aligned to the left (Right click the desktop -> Align -> Left).
3. Create two files and place them next to each other.
4. (Optionally) set wallpaper to a black image (Right click the desktop -> Desktop and Wallpaper -> Color -> #000000).

OBSERVED RESULT
The left row will have a blurrier filename compared to the second row with the default icon alignment.

EXPECTED RESULT
The filenames should be sharp on every row.

SOFTWARE/OS VERSIONS
Linux: Fedora 41
KDE Plasma Version: 6.3.1 
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2

ADDITIONAL INFORMATION
- I can reproduce this problem with a single monitor setup using a 27 inch 1440p monitor. 
- This also occurs when using a dual monitor setup using 125% (1440p monitor) and 175% scaling (4k monitor). Made sure to logout/login before re-testing.
Comment 1 madness742 2025-02-24 17:49:30 UTC
Created attachment 178831 [details]
Aligned desktop right to left, positioned in the upper left corner.
Comment 2 Thomas Bertels 2025-03-10 12:23:22 UTC
You probably mean column instead of row.
Comment 3 madness742 2025-05-05 14:29:34 UTC
Defining the following global environment variable has solved the blurriness: `QT_SCALE_FACTOR_ROUNDING_POLICY=Ceil`.

Interestingly, this has also fixed the weird text rendering I'd see in certain places, such as the digital clock settings. (Unrelated to this bug report)
Comment 4 Nate Graham 2025-05-05 14:32:44 UTC
That environment variable essentially turns off fractional scaling support entirely, so KWin is downscaling from an integer scale. This works, but generates a *different* type of blurriness and also wastes CPU and GPU resources and power. So I'm afraid we can't consider that as a fix; we'll need to find the actual cause here and fix it.

It would be helpful if we could find a 100% reproducible test case for the bug. So far I have not been able to trigger it.
Comment 5 madness742 2025-05-05 17:11:26 UTC
(In reply to Nate Graham from comment #4)
> So I'm afraid we can't consider that as a fix; we'll
> need to find the actual cause here and fix it.
Apologies, I should've phrased it differently. I meant it as a workaround (for myself) while the bug gets a proper fix.

> It would be helpful if we could find a 100% reproducible test case for the
> bug. So far I have not been able to trigger it.
I've also been testing it on my ThinkPad T400 (2008) at 125% scaling (1280x800) with #ff1616 as my wallpaper colour, and I can reproduce it using the steps from my first comment. Sadly I have no other machines to test on, but both my desktop (AMD/AMD) and laptop (Intel/Intel) seem to be affected. 

Don't have much to add besides a higher resolution (2560x1440) will make the issue much more apparent. At least compared to 1280x800. On the laptop the affected rows are also different for some reason.

Linux: Fedora 41
KDE Plasma Version: 6.3.4 
KDE Frameworks Version: 6.13.0
Qt Version: 6.8.2
Kernel: 6.14.4
CPU: Intel Core 2 Duo T9400
GPU: Intel GM45 Express chipset
Comment 6 Nate Graham 2025-08-13 22:33:57 UTC
There have been a lot of fixes for desktop icon positioning issues recently; can anyone still reproduce this one in Plasma 6.4.4 or later? Thanks!
Comment 7 madness742 2025-08-17 10:53:30 UTC
(In reply to Nate Graham from comment #6)
> can anyone still reproduce this one in Plasma 6.4.4 or later?

The first column still looks a little bit fuzzy on my 1440p monitor. When increasing the system font size by 2 points (pt) it's hard to notice the fuzzyness, but I do notice that the font is slightly darker for some reason.

Operating System: Fedora Linux 42
KDE Plasma Version: 6.4.4
KDE Frameworks Version: 6.17.0
Qt Version: 6.9.1
Kernel Version: 6.15.9-201.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Comment 8 madness742 2025-08-17 10:54:12 UTC
Created attachment 184176 [details]
Behaviour on 6.4.4.
Comment 9 madness742 2025-08-17 10:54:33 UTC
Created attachment 184177 [details]
Behaviour on 6.4.4 (increased font size).
Comment 10 Thomas Bertels 2025-08-19 11:57:36 UTC
Is this Wayland specific or can you reproduce it with X11?
Comment 11 madness742 2025-09-13 15:02:47 UTC
(In reply to Thomas Bertels from comment #10)
> Is this Wayland specific or can you reproduce it with X11?

This bug is Wayland specific.