Bug 455370

Summary: Unable to use alternative Window Managers
Product: [Plasma] kwin Reporter: Adam Tazul <adam_tazul>
Component: generalAssignee: KWin default assignee <kwin-bugs-null>
Status: REPORTED ---    
Severity: normal CC: adam_tazul, Hi-Angel, kde, natalie_clarius, skeletonadventure
Priority: NOR Flags: adam_tazul: X11+
Version: 5.25.0   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed In:
Attachments: Example script, launching XMonad as the Window Manager
Example .desktop file from /usr/share/xsessions/, launching XMonad as the Window Manager

Description Adam Tazul 2022-06-15 23:06:38 UTC
Created attachment 149767 [details]
Example script, launching XMonad as the Window Manager

SUMMARY
(Sorry if this is not in the right section, I'm not 100% sure where this bug falls)
In previous versions of KDE Plasma, setting the KDEWM environment variable to another Window Manager on your system would force Plasma to spawn that as the Window Manager in place of Kwin. Since 5.25, no matter what method is used to set the environment variable.

STEPS TO REPRODUCE
1. Install and set up an alternative Window Manager of choice for use with KDE Plasma (X11)
2. Set the KDEWM environment variable using a pre-startup script in ~/.config/plasma-workspace/env/

OBSERVED RESULT
KDE Plasma spawns Kwin

EXPECTED RESULT
KDE Plasma spawns the specified Window Manager

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux Rolling, all testing and unstable repo's enabled
Kernel version: 5.18.3-arch1-1
(available in About System)
KDE Plasma Version: 5.25.0
KDE Frameworks Version: 5.95.0
Qt Version: 5.15.4

ADDITIONAL INFORMATION
N/A
Comment 1 Adam Tazul 2022-06-15 23:12:07 UTC
(In reply to Adam Tazul from comment #0)
> Since 5.25, no matter what method is used to set the environment variable.

No matter what is set as KDEWM, it spawn Kwin instead of your WIndow Manager of choice***
Comment 2 Adam Tazul 2022-06-15 23:13:50 UTC
Created attachment 149768 [details]
Example .desktop file from /usr/share/xsessions/, launching XMonad as the Window Manager
Comment 3 Antonio Rojas 2022-06-16 06:38:30 UTC

*** This bug has been marked as a duplicate of bug 439481 ***
Comment 4 skeletonadventure 2022-06-17 00:24:25 UTC
(In reply to Antonio Rojas from comment #3)
> 
> *** This bug has been marked as a duplicate of bug 439481 ***

These are not duplicates, as evidenced by the "steps to reproduce". In 439481 the environment variable KDEWM is not set, in this bug report it has been set, and as described by https://userbase.kde.org/Tutorials/Using_Other_Window_Managers_with_Plasma this should result in the specified binary being started instead of Kwin.
Comment 5 skeletonadventure 2022-06-17 00:46:46 UTC
My bad upon further reading, it seems the issues are similar, though still a key difference in the use of systemdboot. I am to assume the KDEWM variable feature been silently removed?
Comment 6 Antonio Rojas 2022-06-17 06:05:25 UTC
(In reply to skeletonadventure from comment #5)
> My bad upon further reading, it seems the issues are similar, though still a
> key difference in the use of systemdboot. 

It's not. You are using systemd boot because that's the default in 5.25.
Comment 7 Adam Tazul 2022-06-24 12:45:59 UTC
(In reply to Antonio Rojas from comment #6)
> It's not. You are using systemd boot because that's the default in 5.25.

Shouldn't the KDEWM environment variable be read when using systemd boot?
Comment 8 Johannes Jordan 2022-07-03 11:00:33 UTC
Defaulting to systemd boot is a regression for any users of custom WMs. The update simply breaks the setup.

Also following the tutorial doesn't work anymore: https://userbase.kde.org/Tutorials/Using_Other_Window_Managers_with_Plasma

If KDEWM variable cannot be supported, there should be at least a guideline on how to use a custom WM with newer Plasma versions.
Comment 9 Natalie Clarius 2022-08-10 00:48:25 UTC
Instructions on how to run a custom WM with systemd boot enabled can be found in the Arch wiki: https://wiki.archlinux.org/title/KDE#Use_a_different_window_manager

TL;DR: Create a systemd user unit for your preferred WM and mask the kwin service.

This should be updated on https://userbase.kde.org/Tutorials/Using_Other_Window_Managers_with_Plasma.