Treeland single-wayland sessions are not bound back to dde-session-pre.target shutdown

[zccrs]

Summary

For single-wayland Treeland sessions, stopping the user compositor does not tear down the user session target graph.

The result is a half-alive session: treeland.service is gone, but dde-session and the rest of the user target stack can remain active.

Why this happens

dde-session starts the session target chain like this:

• dde-session.target
• dde-session-initialized.target
• dde-session-core.target
• dde-session-pre.target

Treeland's user compositor unit is installed into dde-session-pre.target.wants/, and it has:

• Requisite=dde-session-pre.target
• PartOf=dde-session-pre.target
• Before=dde-session-pre.target

But dde-session-pre.target itself does not require the compositor unit back.

So the relationship is one-way:

• starting the target starts Treeland
• stopping Treeland does not stop the target chain

treeland.service itself also only unsets environment variables on stop. It does not trigger dde-session-shutdown.target.

Reproduction

I reproduced this with a minimal systemd --user setup that mirrors the shipped target relationships.

With the current relationship:

1. Start dde-session-pre.target
2. Start treeland.service
3. Stop treeland.service

Observed result:

• treeland.service stops
• dde-session-pre.target stays active
• the session target graph remains alive

That matches the current unit design in-tree.

Why this matters

For single-wayland sessions, the compositor is not just another helper. If it disappears, the session is effectively broken.

Today that means a manual systemctl --user stop treeland.service, a compositor crash, or some restart path can leave a headless session behind instead of producing a clean shutdown transaction.

Proposed direction

Bind dde-session-pre.target back to the compositor unit for Treeland single-wayland sessions.

The simplest systemd-side version I validated is:

[Unit]
Requires=treeland.service
After=treeland.service

on dde-session-pre.target for the Treeland session path.

In the same reproducer, that changes the behavior to:

• stop treeland.service also stops dde-session-pre.target
• the half-alive session state disappears
• restart treeland.service becomes a coherent transaction again

If making dde-session-pre.target compositor-specific is too broad, an equivalent Treeland-specific session wrapper target would also work.

Related files

In dde-session:

• systemd/dde-session-pre.target
• systemd/dde-session-core.target
• systemd/dde-session-initialized.target
• systemd/dde-session-manager.service.in

In treeland:

• misc/systemd/dde-session-pre.target.wants/treeland.service.in
• misc/systemd/dde-session-shutdown.target.wants/treeland-session-shutdown.service