Bug#1118702: Allow changing the X11 keyboard layout via org.freedesktop.locale1

[Aaron Rainbolt]

Package: systemd
Version: 257.8-1~deb13u2
Severity: normal
X-Debbugs-Cc: adrelanos at whonix.org, arraybolt3 at gmail.com

Currently, Debian's systemd package ships a file at
/usr/share/dbus-1/system.d/systemd-localed-read-only.conf, which
effectively turns off the ability to use systemd-localed to change the
locale, console keymap, or X11 keymap, due to the fact that Debian uses
other mechanisms for controlling these things.

Unfortunately, this limitation causes serious breakage when using
Calamares to install Debian with a Wayland-based desktop. Under X11,
Calamares is able to set the keyboard layout in other ways, but under
Wayland, the de-facto correct way to set the running Wayland
compositor's keyboard layout on the fly in a compositor-agnostic manner
is to use org.freedesktop.locale1's SetX11Keyboard interface, which is
walled off by this configuration file presumably because the interface
doesn't work as expected at the moment. This means on Wayland-based
desktops, if the user selects a language or keyboard layout other than
the one that was set when Calamares was launched, the installed system
will end up with that keyboard layout set, but the live system will
continue to use the original layout.

This can result in serious issues if the live system boots with a US
English keyboard layout, the user changes the keyboard layout to
German, and then attempts to type a long, secure LUKS passphrase or
user password that happens to include a key like 'z' or 'y' (due to
keys not being where they are expected to be, the user will likely end
up locked out of their system or at least have difficulty getting in).

Other than systemd-localed, the way to change a keyboard layout on the
fly varies widely from compositor to compositor. KWin has (I think)
some internal interface that, to my awareness, isn't supposed to be
used by anything other than KDE components like systemsettings. labwc
uses a file at ~/.config/labwc/environment; you write XKB environment
variables into that file, then you send a SIGHUP to the labwc process.
Other compositors likely have different mechanisms. Avoiding the use of
systemd-localed in Calamares is therefore virtually impossible, and
as Calamares tries to use a distro-agnostic approach to the majority of
their code, they would be unlikely to accept patches to add all of these
different methods of changing keyboard layouts.

Based on looking at
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=608457, it looks like
fully integrating systemd-localed with Debian is not an easy job, and
it's not entirely clear to me what all still needs done to finish this.
But if it was possible to *just* set the X11 keymap using
systemd-localed, even just temporarily, that would be enough to get
Calamares working most likely.

Depending on how my workplace allocates my time, I might be able to help
with work needed to get this fixed in Forky, if someone can point me
towards what to work on.
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