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/xmonad-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, XMonad 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 XMonad to participate in those
specifications.
The "GNOME Flashback (Xmonad)" session *does* set XDG_CURRENT_DESKTOP, but
to a value that is indistinguishable from the ordinary GNOME Flashback
session with the metacity window manager, and I don't know whether that's
the most appropriate thing for the purposes of desktop-specific
configuration or not.
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 xmonad
* reboot
* Log in as the user account, selecting "XMonad" from the menu of
possible X11 sessions
* In a ssh session as the same user, run:
systemctl --user show-environment
* apt install gnome-session-flashback
* Repeat for the "GNOME Flashback (Xmonad)" session
(I couldn't work out how to open a shell in an otherwise unconfigured
XMonad session, but in any case 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. XMonad seems to be its
own thing rather than being based on another desktop environment or
window manager, so
XDG_CURRENT_DESKTOP=XMonad
would seem appropriate.
This would allow the XMonad session to have its own
desktop-environment-specific mimeapps.list or portals.conf(5), for
example /usr/share/xdg-desktop-portal/xmonad-portals.conf.
For XMonad's GNOME Flashback variant, I don't know whether
XDG_CURRENT_DESKTOP should be set to GNOME-Flashback:GNOME (exactly
the same as GNOME Flashback with metacity), or whether it would be better
to set it to something like XMonad-GNOME-Flashback:GNOME-Flashback:GNOME
so that XMonad's GNOME Flashback variant can have its own portal
configuration, mimeapps.list, OnlyShowIn/NotShowIn, etc. if it wants to
(in principle someone could develop a portal backend similar to
xdg-desktop-portal-gtk that works better with tiling window managers,
although I'm not aware of such a thing having been written).
Actual result
=============
In the XMonad session, 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 XMonad 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.
For XMonad's GNOME Flashback variant, XDG_CURRENT_DESKTOP is currently set
to GNOME-Flashback:GNOME (exactly the same as GNOME Flashback with metacity),
so it will always use the same portal configuration, etc. as
gnome-session-flashback (see #1050799).
Suggested fix
=============
Add a sequence of semicolon-separated desktop environment names to
/usr/share/xsessions/xmonad.desktop, most likely just "XMonad":
DesktopNames=XMonad;
(For example, icewm and windowmaker use "ICEWM" and "WindowMaker" in
their equivalent xsessions file.)
And then create a /usr/share/xdg-desktop-portal/xmonad-portals.conf
with whatever portal backends are desired for an XMonad 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.
For XMonad's GNOME Flashback variant, there are two options. If it's
intentional that it is configured the same as the metacity-based GNOME
Flashback session in all respects (portals, mimeapps.list,
OnlyShowIn/NotShowIn, etc.) then it's OK to leave it as-is, with
"DesktopNames=GNOME-Flashback;GNOME;". Or, if it might be desirable to give
it its own desktop-specific configuration, then it should have something
like "DesktopNames=XMonad-GNOME-Flashback;GNOME-Flashback;GNOME;".
Thanks,
smcv