Bug 424591

Summary: QML-based content in System Settings shell (i.e sidebar and home page) is blurry with HiDPI
Product: [Plasma] kwin Reporter: Nate Graham <nate>
Component: wayland-genericAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED UPSTREAM    
Severity: normal CC: elman, kde, nicolas.fella
Priority: NOR    
Version First Reported In: git master   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Discover crisp, System Settings blurry

Description Nate Graham 2020-07-23 22:08:34 UTC
Created attachment 130353 [details]
Discover crisp, System Settings blurry

All KDE software from git master as of this afternoon, on a system with a 4K screen, using a 250% scale factor.

In System Settings, the QML-based sidebar and home screen are blurry for me with the above setup. This does not affect any KCMs, just the QML-based parts of the shell. See attached photo (not a screenshot since Spectacle can't take high DPI screenshots without losing precision, which would hide the problem in this case).

This problem is not seen in QWidgets-based KDE apps, nor other QML-based apps; just System Settings.
Comment 1 David Edmundson 2020-07-23 22:34:50 UTC
At that point it's almost certainly an issue with QQuickWidget rather than kwin.

But as per plasma rules, I'll leave open till we have a Qt bug report/patch
Comment 2 Nicolas Fella 2020-07-23 23:31:52 UTC
I do see blurryness/pixelation issues in QML KCMs as well.

When opening the same KCMs in plasma-settings it works fine, which would support the QQuickWidget theory
Comment 3 David Edmundson 2020-07-24 09:04:28 UTC
Can you confirm a resize "fixes" it.

I put in some debug into QQuickWidget, it seems the initial backing store has a devicePixelRatio of 1 when the FBO gets made. Then it doesn't update correctly.
Comment 4 Nicolas Fella 2020-07-24 09:08:36 UTC
Yes, resizing does seem to help
Comment 6 Nate Graham 2020-07-24 17:54:01 UTC
Thanks David!
Comment 7 David Edmundson 2020-10-14 16:18:37 UTC
*** Bug 427704 has been marked as a duplicate of this bug. ***