Bug 374647

Summary: HiDPI display gets unwanted partial scaling
Product: [Plasma] kwin Reporter: Szymon Łągiewka <bugs-kde>
Component: wayland-genericAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED DOWNSTREAM    
Severity: normal    
Priority: NOR    
Version First Reported In: 5.8.5   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: attachment-30735-0.html

Description Szymon Łągiewka 2017-01-06 18:20:51 UTC 
My screen is HiDPI - 3200x1800 on a 13.3" laptop. Scaling times 2 under Wayland look generally the same as under X - it pretty much covers everything.

The problem is when scaling is set to 1. Effectively this should mean that nothing will be scaled as it does under X. On my Wayland session - I get partial scaling, which seems to be giving me scaling by the factor even greater than 2.

What is scaled (unwanted):
Plasma elements such as panels (i.e. drop-down from system tray), krunner
Fonts in UI - i.e. system settings or dolphin. It also happens for window title panel text but not the panel itself. In result the text does not fit in the title panel.

What is not scaled (wanted):
Applications in general, i.e. Vivaldi is not informed about scaling and the UI along with websites are not being scaled. Other software I've opened to see effects: KeePassX 2, Slack, Messenger for Desktop, PhpStorm

My fonts settings are varying from 8-10. Anit-aliasing - system settings. Force DPI is unchecked.
Comment 1 Martin Flöser 2017-01-07 08:12:15 UTC 
Created attachment 103249 [details]
attachment-30735-0.html

How the applications scale their UI is not under control of the Wayland compositor. What you see is how Qt scales fonts based on DPI. Unlike on X11 Qt uses the correct value. It is different to how it is on X11, but I would rather say the behavior on X11is wrong.

Anyway forcing font DPI addresses the issue.
Comment 2 Szymon Łągiewka 2017-01-12 20:26:28 UTC 
I can confirm that forcing font DPI makes unscaled Plasma on HiDPI screen look tiny again.