As well as being available as a window manager to integrate into some
larger environment, Blackbox behaves like a very small desktop environment
in its own right, by providing a /usr/share/xsessions/blackbox.desktop
which can be selected on entry to a display manager such as lightdm.
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/blackbox-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, Blackbox 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 Blackbox 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 blackbox
* reboot
* Log in as the user account, selecting "Blackbox" 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. Blackbox seems to be its
own thing rather than being based on another desktop environment, so
XDG_CURRENT_DESKTOP=Blackbox
would seem appropriate.
This would allow the Blackbox session to have its own
desktop-environment-specific mimeapps.list or portals.conf(5), for
example /usr/share/xdg-desktop-portal/blackbox-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 Blackbox 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/blackbox.desktop, most likely just "Blackbox":
DesktopNames=Blackbox;
(For example, icewm and windowmaker use "ICEWM" and "WindowMaker" in
their equivalent xsessions file.)
And then create a /usr/share/xdg-desktop-portal/blackbox-portals.conf
with whatever portal backends are desired for a Blackbox 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