Bug 461879

Summary:	Zoom icon is pixelated in window Switcher at 200% scaling
Product:	[Plasma] kwin	Reporter:	frederic.parrenin <frederic.parrenin>
Component:	tabbox	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	normal	CC:	nate, uhhadd
Priority:	NOR
Version First Reported In:	5.26.3
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	.png screenshot of the task switcher

Description frederic.parrenin@univ-grenoble-alpes.fr 2022-11-15 18:03:09 UTC

I have a debian Bookworm machine with KDE/Wayland.
I have a 4k display with I use with a 200% scaling.
I use the Zoom software for visioconference.
I remarked that the Zoom icon in the Window switcher is pixelated.
The problem does not show in Gnome, and I checked that the Zoom icon in /usr/share/pixmaps/ is high resolution.
So I suspect a problem with KDE.

STEPS TO REPRODUCE
1. Use KDE/Wayland on a 4k display with 200% scaling
2. Open Zoom
3. Use the Window switcher

OBSERVED RESULT
The Zoom icon is pixelated

EXPECTED RESULT
The Zoom icon should be high resolution

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Debian Bookworm
(available in About System)
KDE Plasma Version: 5.26.3
KDE Frameworks Version: 5.98.0
Qt Version: 5.15.6

Comment 1 Nate Graham 2022-11-15 19:09:42 UTC

Can you attach a screenshot?

Comment 2 frederic.parrenin@univ-grenoble-alpes.fr 2022-11-17 19:24:52 UTC

Created attachment 153844 [details]
.png screenshot of the task switcher

Attached a screenshot.
I forgot to say that this is with the medium-default task switcher.

Comment 3 Nate Graham 2022-11-18 15:55:53 UTC

Thanks for the screenshot. So there are three elements at play here:
1. Zoom sets a custom icon for its window, and it uses a small raster image that looks bad when scaled up
2. KWin honors that image and displays it in the Task Switcher
3. You're using the "Large Icons" Task Switcher, which makes the icons quite large and so you see pixelation when the source image is small due to #1

In the past, #2 was only done on X11; on Wayland, KWin used the icon from the app's desktop file. However it looks like that changed recently to unify the behavior across X11 and Wayland. That makes this a duplicate of Bug 351055.

*** This bug has been marked as a duplicate of bug 351055 ***

Comment 4 frederic.parrenin@univ-grenoble-alpes.fr 2022-11-20 17:25:41 UTC

Hi Nate, thanks for the detailed reply.
Regarding 1., I am a bit surprised.
When I list the files in the Zoom package, I see two Zoom icons:
/usr/share/pixmaps/Zoom.png
/usr/share/pixmaps/application-x-zoom.png
Both of them are high-resolution.
How did you see that custom-icon is low-res?

Comment 5 Nate Graham 2022-11-21 21:50:52 UTC

It's up to Zoom's code to determine what icon to set the window to. There's no way of knowing that it's specifically chosen one of those. It could be a small one bundled into the app itself.

Comment 6 frederic.parrenin@univ-grenoble-alpes.fr 2022-11-22 17:21:57 UTC

Hi Nate, thanks for the explanation.
So, I reported also the bug to Zoom, so that they provided a higher-res custom icon.