Bug 486416

Summary:	plasma6: virtualbox and differnet scale factors on 2 monitors impacts vbox-display quality
Product:	[Plasma] kwin	Reporter:	slartibart70
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED DOWNSTREAM
Severity:	normal	CC:	kde, nate
Priority:	NOR	Keywords:	multiscreen
Version First Reported In:	6.0.4
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description slartibart70 2024-05-01 19:58:06 UTC

I have the following setup:
Laptop monitor 2880x1800
4K monitor 3840x2160

Since plasma6, setting the laptop screen to 125% works almost fine, until you start virtualbox (maybe other apps as well, but vbox is a nice example here)

It is sufficient to open the virtualbox main window and change the scale-factor of the laptop screen from 125% to 100% (other values will do as well)
Changing scale-values immediately has an effect on the vbox-window size.
This would be still fine, but if you start the virtual-machine, then the screen-size (here: windows11) is reported way bigger - depending on the scale factor.
This has the effect, that windows thinks it has more pixels for the area covered by the vm-display window resulting in pixelated fonts and way too small ui-elements.
You can counter-steer by increasing windows' scale factor as well, but the result is never as clear as if all settings (windows and plasma) are set back to 100%

I would consider this a bug...
Your thoughts?

===
Operating System: Fedora Linux 40
KDE Plasma Version: 6.0.4
KDE Frameworks Version: 6.1.0
Qt Version: 6.7.0
Kernel Version: 6.8.8-300.fc40.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 PRO 7840U w/ Radeon 780M Graphics
Memory: 58,6 GiB of RAM
Graphics Processor: AMD Radeon Graphics
Manufacturer: LENOVO
Product Name: 21K5000JGE
System Version: ThinkPad P14s Gen 4

Comment 1 slartibart70 2024-05-01 20:22:04 UTC

some more info:

i just discovered, that vbox is still X11 (surprise!)
I did play with the systemsettings > display config > legacy applications (x11)
and modified
[ ] 'apply scaling themselves'  to
[x] 'scaled by the system'

Despite the fact that the information-popup says otherwise, this seems to help in the vbox case.
Fonts and ui elements are crisp again (regardless of the scaling in windows) independent of plasma scale-factors applied

Still annoying, though, because this is a global setting.
Can we apply such a behaviour application - wise? (e.g. only for vbox?)

Comment 2 Nate Graham 2024-08-16 16:11:08 UTC

Unfortunately this is systemwide, not per-application.

If the app is buggy with "apply scaling themselves", that means it's an app bug, I'm afraid.