Bug 465965

Summary: blurry red-on-black and black-on-red text with high DPI scaling on Plasma Wayland with Intel UHD Graphics 770
Product: [Plasma] kwin Reporter: Be <be.0>
Component: wayland-genericAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED NOT A BUG    
Severity: normal CC: nate
Priority: NOR    
Version First Reported In: 5.26.5   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Kate with Breeze Dark
Konsole with red text on black background
black text on red background in LibreOffice
red text on black background in LibreOffice
red text on white background in LibreOffice (looks okay)
Kate with Breeze Light (looks okay)
close up photo of Konsole with red text on black

Description Be 2023-02-17 22:27:07 UTC
Created attachment 156394 [details]
Kate with Breeze Dark

SUMMARY
In Plasma Wayland sessions, the interface of red text on a dark background or dark text on a red background is blurry using my Intel UHD Graphics 770 when the screen scale factor is 200%. See attached screenshots.

STEPS TO REPRODUCE
1. Log into Plasma Wayland session
2. Set monitor scale factor to 200% in Display and Monitor system settings
3. Open an application with red text

OBSERVED RESULT
Red text is blurry.

EXPECTED RESULT
Text scales smoothly.

SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 37
KDE Plasma Version: 5.26.5
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
Kernel Version: 6.1.11-200.fc37.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 24 × 12th Gen Intel® Core™ i9-12900K
Memory: 62.1 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 770
Manufacturer: ASUS

ADDITIONAL INFORMATION
I am unable to reproduce this when using my GeForce RTX 3060 Lite Hash Rate, using Plasma X11, or setting the screen scale factor to 100%.
Comment 1 Be 2023-02-17 22:27:40 UTC
Created attachment 156395 [details]
Konsole with red text on black background
Comment 2 Be 2023-02-17 22:27:59 UTC
Created attachment 156396 [details]
black text on red background in LibreOffice
Comment 3 Be 2023-02-17 22:28:28 UTC
Created attachment 156397 [details]
red text on black background in LibreOffice
Comment 4 Be 2023-02-17 22:29:14 UTC
Created attachment 156398 [details]
red text on white background in LibreOffice (looks okay)
Comment 5 Be 2023-02-17 22:29:34 UTC
Created attachment 156399 [details]
Kate with Breeze Light (looks okay)
Comment 6 Be 2023-02-17 22:34:01 UTC
I am unable to reproduce this with Weston or GNOME (Wayland) running the same applications.
Comment 7 Be 2023-02-17 22:57:13 UTC
Created attachment 156403 [details]
close up photo of Konsole with red text on black

I can see the blurriness when looking at the attached screenshots in Plasma Wayland, but not when viewing the screenshots in GNOME. So here is a close up photo of my monitor taken with my phone camera. Notice the jagged edges of the text "HEAD detatched at" compared to the surrounding text, particularly the rounded edges of "b" and "d" and the slanted edges of "A".
Comment 8 Nate Graham 2023-02-22 02:21:44 UTC
I'm genuinely unable to notice any blurriness in the red text in those screenshots. I'm using a similar setup (Intel UHD620, 200% scale, Wayland) and don't see it either.

Any chance you can attach a screenshot that makes it more obvious?
Comment 9 Be 2023-02-22 18:39:08 UTC
Those screenshots were taken with Spectacle. I'm not sure if this bug can be captured by screenshots... which may hint that the bug is pretty low down in the graphics stack. FWIW, I'm using a Samsung QN32Q60AAFXZA 32 inch 3840 x 2160 monitor connected via HDMI.
Comment 10 Be 2023-02-22 21:48:52 UTC
Are you able to see the difference with the photo rather than the screenshots? It's most prominent comparing the red "A" with the purple "A".
Comment 11 Be 2023-02-22 23:30:30 UTC
Well this is interesting. I tried plugging my monitor into my laptop (same software setup, Plasma Wayland with Fedora 37) with a USB-C to HDMI cable and couldn't reproduce the issue. Then I tried using the same cable with my desktop and couldn't reproduce the issue. Then I tried switching back to the HDMI to HDMI cable which reproduced the issue, fiddled around in the monitor's settings, and now the issue is gone. I'm not sure what changed. I think the issue when away when I enabled "game mode" on the monitor, but then I tried disabling it and couldn't reproduce it... anyway, it seems the problem was something in the monitor rather than my desktop computer.
Comment 12 Nate Graham 2023-02-22 23:58:55 UTC
Aha, makes sense! Monitors often have processing modes that will produce weird effects for normal desktop computer usage.