Bug 465168

Summary:	blurry text with fractional scaling
Product:	[Plasma] kwin	Reporter:	Tom Englund <tomenglund26>
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED NOT A BUG
Severity:	normal
Priority:	NOR
Version First Reported In:	git master
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Tom Englund 2023-02-02 13:05:36 UTC

since the move seems to be going from force font dpi to display scaling, i got to report it makes fonts and various components blurry as of currently on plasma 5.27 beta. this is with forcing font dpi to 144 https://i.imgur.com/0ZaR2WG.png , and this is with scaling 150% which makes them roughly the same size. https://i.imgur.com/p6U5CoT.png

SUMMARY
with fractional scaling instead of forcing font dpi you get blurry text all over, most noticeably on the desktop icons on the screenshots.


STEPS TO REPRODUCE
1. Change the scaling and compare text with force font dpi.


OBSERVED RESULT
blurry text

EXPECTED RESULT
crisp fonts.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.26.90
KDE Frameworks Version: 5.102.0
Qt Version: 5.15.8
Kernel Version: 6.1.8-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5800H with Radeon Graphics
Memory: 30,7 GiB of RAM
Graphics Processor: AMD Radeon Graphics
Manufacturer: Acer
Product Name: Nitro AN515-45

Comment 1 Vlad Zahorodnii 2023-02-02 16:35:54 UTC

We implemented fractional scaling protocol in 5.27, BUT the client side also needs to support it. Support for fractional scaling is missing in Qt 5 (kwin ceil()s the scale factor and downscales client buffers so the fonts don't look crisp anymore). Reopen this bug report if you see issues in apps using Qt 6.5 or newer, which should support fractional scaling.