Bug 423542

Summary:	Incorrect window scaling on highdpi monitor
Product:	[Plasma] kwin	Reporter:	Nicolas Fella <nicolas.fella>
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	nate
Priority:	NOR	Keywords:	regression
Version First Reported In:	git master
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:	https://invent.kde.org/plasma/kwin/-/commit/617650d4405774358118866062ece477401652f2	Version Fixed/Implemented In:	5.20
Sentry Crash Report:
Attachments:	Falkon screen photo

Description Nicolas Fella 2020-06-26 11:57:52 UTC

I have a 4K monitor with 2x scaling and a FHD monitor with 1x scaling. When I open a window on the 4K monitor the content only fills the top left quarter of the window. Once I resize the window it works as expected. Happens with both Qt apps (tested with Falkon) and GTK apps (tested with Gnome clocks). It does not seem to affect XWayland apps (tested with Firefox).

Bisecting KWin leads to 31ea780d7996dd06d34243aeb92386e5571d821e

Qt is built from 5.15 branch

Comment 1 Nicolas Fella 2020-06-26 12:07:57 UTC

Created attachment 129693 [details]
Falkon screen photo

Comment 2 Vlad Zahorodnii 2020-07-01 07:28:21 UTC

If you're still able to reproduce this bug, can you please provide a WAYLAND_DEBUG output? (falkon is rendered just fine on my machine)

Comment 3 Vlad Zahorodnii 2020-07-01 07:30:40 UTC

I believe that it has something to do with not discarding window quads if the frame geometry didn't change, but the buffer geometry did change.

Comment 4 Nicolas Fella 2020-07-06 16:03:45 UTC

It seems to be fixed, likely because of https://invent.kde.org/plasma/kwin/-/merge_requests/92