Arch Linux

Didn't realize the PNG version was over the 2MB file size limit, converted and uploaded

A very similar thing happens to me, I have a 1440 beside a 1080 monitor and a non-default vertical offset between their relative positions (see settings image attached) and after the upgrade my wallpaper on my small monitor is misaligned with a large black bar across 20% of the screen.

Same here, I have two 2560*1440 monitors connected to a 1920*1080 laptop which led is off.
I can turn off the second monitor and then turn it on again to work around this issue.
The first screenshot is incorrect, and the second screenshot is correct.
It's should be a QT problem, I downgraded the qt packages with

```
pacman -U qt5-base-5.15.0-5-x86_64.pkg.tar.zst qt5-declarative-5.15.0-2-x86_64.pkg.tar.zst qt5-location-5.15.0-1-x86_64.pkg.tar.zst qt5-multimedia-5.15.0-1-x86_64.pkg.tar.zst qt5-speech-5.15.0-1-x86_64.pkg.tar.zst qt5-svg-5.15.0-1-x86_64.pkg.tar.zst qt5-webchannel-5.15.0-1-x86_64.pkg.tar.zst qt5-x11extras-5.15.0-1-x86_64.pkg.tar.zst akonadi-20.08.1-1-x86_64.pkg.tar.zst fcitx-qt5-1.2.5-1-x86_64.pkg.tar.zst kwin-5.19.5-1-x86_64.pkg.tar.zst libakonadi-20.08.1-1-x86_64.pkg.tar.zst qt5-graphicaleffects-5.15.0-1-x86_64.pkg.tar.zst qt5-networkauth-5.15.0-1-x86_64.pkg.tar.zst qt5-quickcontrols-5.15.0-1-x86_64.pkg.tar.zst qt5-quickcontrols2-5.15.0-1-x86_64.pkg.tar.zst qt5-script-5.15.0-1-x86_64.pkg.tar.zst qt5-sensors-5.15.0-1-x86_64.pkg.tar.zst qt5-tools-5.15.0-3-x86_64.pkg.tar.zst qt5-wayland-5.15.0-1-x86_64.pkg.tar.zst qt5-webengine-5.15.0-5-x86_64.pkg.tar.zst qt5-webkit-5.212.0alpha4-6-x86_64.pkg.tar.zst qt5-xmlpatterns-5.15.0-1-x86_64.pkg.tar.zst
```

and the problem resolved. I then instaled the latest again and the problem reappeared.

I get this as well but I've had this issue for probably half a year at this point. Only thing I can say it that it happened more often when I used nvidia, but it could just be a coincidence.
Lately it's only been the taskbars swapping place, while wallpapers stay correct.

My monitor setup is 2x 2560x1440 displays, with the main one being on the right.

I'm having this issue as well.

Setup:
- dual screen setup where the DisplayPort-0 is the right screen and DisplayPort-1 is the left and primary screen
- a workspace where the left screen contains a workspace view and the right screen contains a directory view
- two control bars: the control bar on the left screen consists of a window bar which only shows windows of the screen. Same for the control bar on the right screen

After upgrading and rebooting, the workspaces are swapped: the right screen shows the workspace view and the left screen shows the folder view. The control bars on the other hand stay on the screen but show the windows for the wrong screen.

When switching the primary screen using kcm nothing happens. When performing this action again the workspace/folder views and/or control bars swap randomly. Sometimes, both window bars only show windows on the right monitor. After changing the screen positions and primary screen settings several times it eventually reaches the preferred state like before the upgrade. But only until a reboot/logout.

Downgrading fixes the problem but this is obviously no solution.

https://codereview.qt-project.org/c/qt/qtbase/+/315447

This patch in qtbase seems to fix the issue. Worth backporting?

If not, this one in plasmashell is a hack that works-around the issue:
https://invent.kde.org/plasma/plasma-workspace/-/merge_requests/292

Above qt patch worked for OpenSUSE, though, so it's probably a better bet.

I can confirm the qt patch I linked above fixes the issue.

Tested with the above patch as well and everything seems to work right once more.