Re: "whether the global keymap C-x 4 will be replaced by a command,"

[Stefan Monnier]

> 2. add a catch-all fallback to ctl-x-4-map and bind it to the command
>    invoked when an unbound key is typed after 'C-x 4'.

I don't know how to implement that in a way that works well enough
(i.e. without suffering from weird corner case behaviors due to
interactions with `input-decode-map`, `function-key-map`, etc...).

`set-transient-map` is the least bad I way I found to provide this kind
of behavior.


        Stefan