Allow switching between all the input sources on the system
gnome-control-center used to allow setting the input sources to be used on the login screen. That functionality was lost in GNOME 40 (see gnome-control-center#1434 (closed)), which leaves us in quite a bad situation.
However, manually configuring the login screen input sources seems like quite a poor design choice: if someone wants to add an input source and have it available on the login screen, they need to configure it twice.
A much better approach would be to allow switching between all the input sources that users on the system have set up. For the default input source, we could then try and be smart. That could be:
- if all the users on the system share the same default input source, use that
- if there's an input source that is configured by all users on the system, use that
- select the last used input source
- don't select an input method by default (I think we assume that passwords are in ascii?)
Per-user keyboard and input method configuration are difficult to incorporate into this approach. However, I wonder if we could ignore that to begin with and see whether it is an issue in practice? In most cases the keyboard input required for login is minimal.