Setting "master" window on primary display breaks multi-screen switching

[JustinTimperio]

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Bug Report
Multi-Monitor Functionality

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Symptom
I have started to experience this bug after updating from last weeks release. It seems after debugging for about an hour, that when a window is set as "master" on the Primary Screen it breaks all kwin screen switching commands for that window. Both my "Window to Desktop #" and "Window to Previous/Next Screen" are completely disabled until a new window is set to "master" on that desktop. The window remains locked even after floating the window. This also entirely destroys any desktops that only have one window active or are layered windows like the "Spread Layout". Additionally, master window behavior does not seem to be reset by a kwin_x11 --replace and remains bugged permanently on any desktop instance on that screen (IE Virtual Desktop 3 and Virtual Desktop 4 on screen 0).

How to Reproduce
Multi-Monitor required

1. Fresh boot followed by a kwin_x11 --replace
2. Set a master window on your Primary Screen then attempt to move it with either "Window to Desktop #" or "Window to Previous/Next Screen"
3. Set a new master window on the Primary Screen and notice that the previously locked window is now free to move across screens while the new window is locked
   .

Expected behavior
Oddly enough snaping windows into new screens with the mouse still works. Just expecting that next and previous screen keys will move my windows.

Environment
OS: Arch Linux x86_64
Host: XPS 15 9560
Kernel: 4.14.88-1-lts
Kwin: 5.14.4-2
Typescript: 3.1.6-1
Resolution: 2560x1440, 2560x1440, 2560x1440
WM Theme: breezeblurred
Krohnkite version: version 0.1, commit= 8023304
KWin scripts in use: Kronhnkite

Notes
I absolutely love the script so far but multi-screen support is my number one priority for any window manager. Unfortunately, due to this bug I have had to disable Kronhnkite on both my Desktop and Laptop since I use multi-screen 80% of the time and it massively disrupts my workflow. If I can be of any assistance debugging this please feel free to ask.

Many Thanks,
Justin

[esjeon]

Thanks for filling out the report. I've been trying to reproduce the bug, but without any success. I tested on my PC(Arch) and 2 VMs(Arch, KDE Neon), but none showed the symptom you described.

Untested variables are:

1. LTS kernel on Arch
2. Intel + NVIDIA graphics setup (XPS 9590). My computer is NVIDA + Ryzen(no IG).
3. Physical multi-monitor. (I use Virtualbox to test multi-monitor setup.)

Well, I'm gonna test these using scrap parts, but no guarantees.

[JustinTimperio]

Thanks for the fast reply.

Currently, I am not running any Nvidia drivers for power saving reasons. It runs on the Intel integrated graphics. I am also doubtful that it is the LTS branch as I have tested this on both. I have Kubuntu on this machine so I can check that tomorrow when I get into the office where my monitors are.

In testing this I think I may have tracked down the issue to more specific circumstances. For some reason when displays are stack vertically things seem to break much more consistently. My work setup has my laptop on the bottom as primary with 2 additional monitors directly above. At home, I have 4 screens which let me test some of the more obscure layouts. When all screens are placed horizontally next to each other everything seems to work fine. Once any screens are stacked vertically though, things start acting weird and seemingly erratic.

I am also more than willing to fund an AWS instance so you can continue your multi-monitor work if access to testbeds/ virtual screens is in an issue for you.

[esjeon]

when displays are stack vertically things seem to break much more consistently

Hmm, stacking vertically did broke the script temporarily, but I still can't reliably break it. But from the debug output while it was broken, I could see that KWin was malfunctioning. It wasn't firing any events at all. I think KWin is suffering internal errors.

I am also more than willing to fund an AWS instance so you can continue your multi-monitor work if access to testbeds/ virtual screens is in an issue for you.

Thanks, but Virtualbox is good enough for testing multihead logic.

[JustinTimperio]

After the 0.2 release, this bug seems to been resolved across all my systems. Thanks for the update!