Bug#1050980: awesome: please set XDG_CURRENT_DESKTOP and use it to configure xdg-desktop-portal

[Simon McVittie]

Package: awesome
Version: 4.3-7
Severity: normal
User: xdg-deskt...@packages.debian.org
Usertags: portals.conf

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/awesome-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, awesome doesn't set XDG_CURRENT_DESKTOP, so for
the purposes of this mechanism, it's not programmatically distinguishable
from any other desktop environment or window manager.

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 awesome 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
* apt install lightdm xorg awesome
* reboot
* Log in as the user account, selecting "awesome" from the menu of
possible X11 sessions
* Open a terminal and run:
env | grep XDG_CURRENT_DESKTOP
systemctl --user show-environment

(It's the systemd activation environment that matters here, more than
`env`, 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. awesome seems to be its
own thing rather than being based on another desktop environment or
window manager, so

XDG_CURRENT_DESKTOP=awesome

would seem appropriate.

This would allow the awesome session to have its own
desktop-environment-specific mimeapps.list or portals.conf(5), for
example /usr/share/xdg-desktop-portal/awesome-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 awesome 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/xsessions/awesome.desktop, most likely just "awesome":

DesktopNames=awesome;

(For example, icewm and windowmaker use "ICEWM" and "WindowMaker" in
their equivalent xsessions file.)

And then create a /usr/share/xdg-desktop-portal/awesome-portals.conf
with whatever portal backends are desired for an awesome 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