Package: weston
Version: 12.0.1-1
Severity: normal
User: xdg-desktop-por...@packages.debian.org
Usertags: portals.conf

In addition to being available as a compositor that is part of
a more comprehensive desktop environment, weston behaves like
a small desktop environment in its own right, by providing a
/usr/share/wayland-sessions/weston.desktop which can be selected on
entry to a display manager such as gdm3.

xdg-desktop-portal 1.17.x introduces a new way to select which portals will
be used for which desktop environments, modelled on mimeapps.list:

- each desktop environment should provide a file like
  /usr/share/xdg-desktop-portal/weston-portals.conf

- the filename is ${DESKTOP}-portals.conf where ${DESKTOP} is the desktop
  environment's entry in $XDG_CURRENT_DESKTOP (the same as the DesktopNames
  from /usr/share/{x,wayland-}sessions/*.desktop), folded to lower case

- sysadmins and users can override this via files named portals.conf or
  ${DESKTOP}-portals.conf in various locations like /etc/xdg-desktop-portal
  and ~/.config/xdg-desktop-portal

But as far as I can tell, weston doesn't set XDG_CURRENT_DESKTOP, so for
the purposes of this mechanism, it's not programmatically distinguishable
from any other equally simple session.

XDG_CURRENT_DESKTOP is also used in pre-existing freedesktop.org standards
like the OnlyShowIn/NotShowIn fields for .desktop files, and the ability to
provide a desktop-environment-specific mimeapps.list. Setting
XDG_CURRENT_DESKTOP would allow weston to participate in those
specifications.

To reproduce
============

* Start from a basic non-GUI virtual machine (I used autopkgtest-build-qemu)
* Ensure that a user account exists and has a password
* apt install gdm3 weston
* reboot
* Log in as the user account, selecting Weston from the menu of
  possible X11/Wayland sessions before entering the password
* Open a terminal and run:
  systemctl --user show-environment

(It's the systemd activation environment that matters here, more than
`echo $XDG_CURRENT_DESKTOP`, because xdg-desktop-portal will typically be
run as a systemd user service.)

Expected result
===============

XDG_CURRENT_DESKTOP should be set to a colon-separated sequence of
desktop environment names, most specific first. For Weston on its own
as a simple desktop environment,

    XDG_CURRENT_DESKTOP=Weston

would seem appropriate?

This would allow the Weston session to have its own
desktop-environment-specific mimeapps.list or portals.conf(5), for
example /usr/share/xdg-desktop-portal/weston-portals.conf.

Actual result
=============

XDG_CURRENT_DESKTOP is unset.

This means that xdg-desktop-portal configuration can only be done via a
non-desktop-specific portals.conf, but that's not really something that a
non-opinionated distribution like Debian can usefully ship in a centralized
way, so each user of Weston who wants a working xdg-desktop-portal will
have to configure it themselves.

At the moment, this is mitigated by xdg-desktop-portal (>= 1.17) having
been patched to fall back to xdg-desktop-portal-gtk as a last-resort
desktop-environment-specific backend, but hard-coding that implementation
isn't really something we should be doing centrally (and the idea was
rejected upstream), so I intend to remove that patch before trixie
is released.

Suggested fix
=============

Add a sequence of semicolon-separated desktop environment names to
/usr/share/wayland-sessions/weston.desktop, most likely just "Weston":

DesktopNames=Weston;

And then create a /usr/share/xdg-desktop-portal/weston-portals.conf
with whatever portal backends are desired for a Weston session,
for example perhaps this:

[preferred]
default=gtk;

Please see portals.conf(5) or its source code
https://github.com/flatpak/xdg-desktop-portal/blob/main/doc/portals-conf.rst
for full details.

Thanks,
    smcv

-- 
This is part of a mass bug filing:
https://lists.debian.org/debian-devel/2023/08/msg00311.html

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