Bug 426795

Summary:	[Wayland] One line of transparent pixels remains on top of maximized windows when using a HiDPI scale factor
Product:	[Plasma] kwin	Reporter:	joseph.chataignon
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	minor	CC:	kde, nate
Priority:	NOR
Version First Reported In:	5.19.5
Target Milestone:	---
Platform:	Manjaro
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	Screenshot of Wayland on Plasma 5.21.4 with 1px transparent line on top of maximized window, and to left of titlebar

Description joseph.chataignon 2020-09-21 06:45:54 UTC

On High-DPI screen with scaling 150%, maximizing windows lets a 1-pixel high line uncovered at the top of the screen. I can see the top line of my desktop wallpaper. This happens under Wayland.

STEPS TO REPRODUCE
1. Have KDE installed and a high-DPI screen
2. Open a Wayland session, set scaling to 150%
3. maximize a window 

OBSERVED RESULT

The window does not cover the screen exactly to the top. A line 1 pixel high stays uncovered by the maximized window.

EXPECTED RESULT
The maximized window should cover the whole screen.


SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.19.5
KDE Frameworks Version: 5.73.0
Qt Version: 5.15.0
Kernel Version: 5.8.6-1-MANJARO
Graphics Processor: Mesa Intel UHD Graphics 620

Comment 1 Paul McAuley 2021-04-19 22:27:33 UTC

Created attachment 137715 [details]
Screenshot of Wayland on Plasma 5.21.4 with 1px transparent line on top of maximized window, and to left of titlebar

I also get this on Wayland with 250% scaling. For me there is also a 1px line on the left edge of the Breeze titlebar. 

In the attached screenshot the line appears purple as this is the colour of the standard Plasma 5.21 wallpaper behind.

Comment 2 Paul McAuley 2021-04-19 22:30:00 UTC

It also occurs at 200%

Comment 3 Paul McAuley 2021-04-19 22:34:43 UTC

Operating System: openSUSE Leap 15.2
KDE Plasma Version: 5.21.4
KDE Frameworks Version: 5.81.0
Qt Version: 5.15.2
Kernel Version: 5.3.18-lp152.72-preempt
OS Type: 64-bit
Graphics Platform: Wayland
Processors: 8 × Intel® Core™ i7-7700HQ CPU @ 2.80GHz
Memory: 31.2 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 630

Comment 4 Nate Graham 2021-04-20 14:55:50 UTC

Cannot reproduce on Wayland FWIW.

Comment 5 Vlad Zahorodnii 2022-01-19 19:00:38 UTC

The renderer in the drm backend used to calculate the viewport size as logical size * scale, it was changed a while ago and it uses the mode size, so this bug should be fixed.