Bug 456855 - KWin titlebar and Xwayland window contents are blurry on certain screen coordinates when fractional scaling is enabled
Summary: KWin titlebar and Xwayland window contents are blurry on certain screen coord...
Status: RESOLVED FIXED
Alias: None
Product: kwin
Classification: Plasma
Component: wayland-generic (other bugs)
Version First Reported In: 5.26.0
Platform: Neon Linux
: NOR normal
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords: regression
Depends on:
Blocks:
 
Reported: 2022-07-18 12:34 UTC by egor21312
Modified: 2023-12-08 12:27 UTC (History)
7 users (show)

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


Attachments
Picture demonstrating the blurriness on the KWin titlebar in contrast to System Settings app contents (in both cases Wayland 125% scale is used) (33.14 KB, image/png)
2022-07-18 12:41 UTC, egor21312
Details
crisp title bar with window closer to 200% screen (357.26 KB, image/png)
2022-10-30 12:56 UTC, Ye Jingchen
Details
blurry title bar with window closer to 150% screen (297.72 KB, image/png)
2022-10-30 12:57 UTC, Ye Jingchen
Details

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Description egor21312 2022-07-18 12:34:31 UTC
STEPS TO REPRODUCE
1. Enable fractional scaling (125% in this case) in Wayland session (and use "Apply scaling themselves" for X11 applications)
2. Drag any window around

OBSERVED RESULT
KWin titlebar rendering becomes blurry when the window is on certain coordinates, in case of X11 windows same applies to the contents

EXPECTED RESULT
KWin titlebar and X11 window contents render crisply regardless of the window position

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE Neon Unstable 220717-0337
KDE Plasma Version: reported the system as 5.25.80
KDE Frameworks Version: 5.97.0
Qt Version: 5.15.5
Comment 1 egor21312 2022-07-18 12:41:20 UTC
Created attachment 150705 [details]
Picture demonstrating the blurriness on the KWin titlebar in contrast to System Settings app contents (in both cases Wayland 125% scale is used)
Comment 2 Ye Jingchen 2022-10-30 12:54:41 UTC
Can confirm this still happens on KDE Plasma 5.26.2, with KF 5.99 and Qt 5.15.6, on Arch Linux.

This behavior is more obvious when using two monitors: one with 200% integer scaling, the other fractional (e.g. 150%), and put the window across the screen border, with the title bar visible on both sides.

When the window is closer to the 200% screen, title bar is pixel sharp (including text, app icon and control buttons) on the 200% screen, and a little bit blurry due to scaling on the 150% screen (which is normal);
However, if the window is moved closer to the 150% screen, title bar suddenly become blurry even on the 200% screen, and more blurry on the 150% screen, more blurry than it was when window is closer to 200% screen. When moved back closer to 200% screen, title bar become crisp again.

The window content is identical in two scenarios above, that is it didn't become more blurry or more crisp when title bar blurriness changes.
Comment 3 Ye Jingchen 2022-10-30 12:56:33 UTC
Created attachment 153324 [details]
crisp title bar with window closer to 200% screen
Comment 4 Ye Jingchen 2022-10-30 12:57:03 UTC
Created attachment 153325 [details]
blurry title bar with window closer to 150% screen
Comment 5 Nate Graham 2022-10-31 18:14:48 UTC
Possibly Bug 460573? Or related to it?
Comment 6 Ye Jingchen 2022-11-01 12:19:11 UTC
(In reply to Nate Graham from comment #5)
> Possibly Bug 460573? Or related to it?

Doesn't seem like the same problem, as I don't see difference between window content, only the title bar is blurry.

However the blurry title bar does seems a bit clearer when maximized, though it's hard to tell whether it's the title bar really changing, or just some scaling artifact disappeared.
Comment 7 David Edmundson 2023-02-15 09:37:26 UTC
Please confirm if this is still an issue on Plasma 5.27, changes were made to this.
Comment 8 Alexander Sanderson 2023-03-08 04:44:44 UTC
I can confirm that this is still an issue in Plasma 5.27
Comment 9 Ye Jingchen 2023-03-08 16:11:48 UTC
This still happens on Plasma 5.27.2: titlebar becoming sharp or blurry depending on window being closer to integer-scaled or fractional-scaled screens.
Comment 10 David Edmundson 2023-12-08 12:27:34 UTC
We can track window title issues here: 467179

The xwayland side is fixed, so I'll close this MR