Bug 474738

Summary:	XWayland apps look blurry when one of screens has fractional scaling enabled
Product:	[Plasma] kwin	Reporter:	indx <l0rmin>
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED INTENTIONAL
Severity:	normal	CC:	aleixpol, alois.ma, caderry, kde, kdedev, kole3600, nate, rohan
Priority:	NOR	Keywords:	multiscreen, usability, wayland-only
Version First Reported In:	5.27.4
Target Milestone:	---
Platform:	Kubuntu
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	VSCode with laptop's montor enabled VSCode with laptop's montor disabled screenshor 1

Description indx 2023-09-20 14:04:05 UTC

SUMMARY
XWayland apps look very good, when I use only one monitor (Laptop's built-in monitor, 150% scaling). But when I use my laptop with a second monitor (Laptop's built-in monitor, 150% scaling + MSI (Primary), 100% Scaling) apps still look good on built-in monitor, but they look blurry on a second monitor, compared to what they look like when I disable built-in screen.


STEPS TO REPRODUCE
1. Login to Plasma Wayland session, set laptop's built-in monitor scaling to 150%.
2. Re-login
3. Launch any XWayland app
4. Move it to the second monitor
5. Compare app's fonts with built-in monitor enabled and disabled

OBSERVED RESULT
Apps look blurry on the second monitor


EXPECTED RESULT
Apps look fine on the second monitor

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Kubuntu 23.04
(available in About System)
KDE Plasma Version: 5.27.4
KDE Frameworks Version: 5.104.0
Qt Version: 5.15.8

ADDITIONAL INFORMATION

Comment 1 indx 2023-09-20 14:05:52 UTC

Created attachment 161749 [details]
VSCode with laptop's montor enabled

Comment 2 indx 2023-09-20 14:06:17 UTC

Created attachment 161750 [details]
VSCode with laptop's montor disabled

Comment 3 Nate Graham 2023-09-20 18:12:00 UTC

Can't reproduce in Plasma 6.

Comment 4 indx 2023-09-20 19:57:56 UTC

Tried on Neon Unstable with P6. Same bug, still reproducible

Comment 5 Nate Graham 2023-09-20 20:05:25 UTC

In that case I am suspecting a problem in the Hidpi support in the apps themselves. Do the affected apps look better on X11 when you with a fractional global scale?

Comment 6 indx 2023-09-21 09:26:40 UTC

On x11 they look better, but x11 supports only global scale, and I need different scales for different screens

Comment 7 Nate Graham 2023-09-21 15:32:55 UTC

Hmm, Ok, then it's not a problem in the apps' own high DPI support.

Can you open System Settings > Display and Monitor, scroll all the way to the bottom, take a screenshot of the window, and attach it here? Thanks!

Comment 8 indx 2023-09-21 16:54:06 UTC

Created attachment 161782 [details]
screenshor 1

Comment 9 indx 2023-09-21 16:54:16 UTC

(In reply to Nate Graham from comment #7)
> Hmm, Ok, then it's not a problem in the apps' own high DPI support.
> 
> Can you open System Settings > Display and Monitor, scroll all the way to
> the bottom, take a screenshot of the window, and attach it here? Thanks!

Added

Comment 10 indx 2023-09-21 20:23:04 UTC

(In reply to Nate Graham from comment #7)
> Hmm, Ok, then it's not a problem in the apps' own high DPI support.
> 
> Can you open System Settings > Display and Monitor, scroll all the way to
> the bottom, take a screenshot of the window, and attach it here? Thanks!

Apply scaling themselves option gives very good-looking apps on laptop's monitor but slightly blurry on external one
Scaled by the system gives very, very blurry apps on laptop's monitor and good-looking on external

Comment 11 David Edmundson 2023-09-21 22:14:09 UTC

It is expected that mixed scales on Xwayland will involve downscaling on one of the two screens. That's unfeasible to change.

One option that might work for you is to edit .config/kwinrc and set:

[Xwayland]
Scale[$i]=2

combined with `Apply scaling themselves`
It'll be downscaled on both monitors but from a much higher source which should hopefully look not blurry. Same as any GTK apps on those monitors.

Comment 12 Nate Graham 2023-09-21 22:18:27 UTC

Could we improve this by running a separate XWayland instance per screen or per process?

Comment 13 Bug Janitor Service 2023-10-06 03:46:27 UTC Comment hidden (spam)

Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!

Comment 14 Bug Janitor Service 2023-10-21 03:45:29 UTC Comment hidden (spam)

This bug has been in NEEDSINFO status with no change for at least
30 days. The bug is now closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

Thank you for helping us make KDE software even better for everyone!

Comment 15 Nate Graham 2024-06-25 22:56:57 UTC

*** Bug 477177 has been marked as a duplicate of this bug. ***

Comment 16 Nate Graham 2024-06-25 22:57:00 UTC

*** Bug 489077 has been marked as a duplicate of this bug. ***

Comment 17 Nate Graham 2024-08-13 22:10:49 UTC

*** Bug 491641 has been marked as a duplicate of this bug. ***

Comment 18 Nate Graham 2024-09-23 18:53:34 UTC

*** Bug 493479 has been marked as a duplicate of this bug. ***