fix herbstluftwm session command with other desktop managers

[fdietze]

Description of changes

Enabling for example xfce and herbstluftwm generates a xsession script like this:

#! /nix/store/7q1b1bsmxi91zci6g8714rcljl620y7f-bash-5.2-p15/bin/bash

# Legacy session script used to construct .desktop files from
# `services.xserver.displayManager.session` entries. Called from
# `sessionWrapper`.

# Start the window manager.
/nix/store/43syrfrpxc3d7dyhbhkh1i3wpzq8knfz-herbstluftwm-0.9.5/bin/herbstluftwm

# Start the desktop manager.
/nix/store/7q1b1bsmxi91zci6g8714rcljl620y7f-bash-5.2-p15/bin/bash /nix/store/hqrwlx6h1bdqq3vbzxladczbql7f0q03-xfce4-session-4.18.2/etc/xdg/xfce4/xinitrc &
waitPID=$!


/nix/store/v0lv3kpj2ppv9k6y48azc6m6m2barasr-dbus-1.14.6/bin/dbus-update-activation-environment --systemd --all


test -n "$waitPID" && wait "$waitPID"

/run/current-system/systemd/bin/systemctl --user stop graphical-session.target

exit 0

Note, that the herbstluftwm command launches a permanently running process, so the following commands will never be executed, until herbstluftwm is quit.

This PR runs herbstluftwm in a background job instead.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[fdietze]

I think I made a mistake here. This change allows using herbstluftwm with xfce, but it breaks the standalone usage of herbstluftwm, because the xsession script quits immediately and therefore also kills the herbstluftwm background process. How can we support both?

[B4rc1]

but it breaks the standalone usage of herbstluftwm, because the xsession script quits immediately and therefore also kills the herbstluftwm background process. How can we support both?

I ran into this issue upon the release of 23.11, would #271198 work in your case?
I think it would since waitPID would be overwritten before waiting for it, could you please test it?

[fdietze]

@B4rc1 Thanks for your effort and sorry for my long silence! I just wanted to test your fix, but currently my internet connection is way too bad...

What I would test:

desktopManager.xfce.enable = true;
windowManager.herbstluftwm.enable = true;

And then try to login with those sessions:

• none+herbstluftwm
• xfce+herbstluftwm

If both just work, we have a fix.