bug#52245: Wishlist: cycle input methods

[Eli Zaretskii <eliz@gnu.org>]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  tor.a.s.kringeland@ntnu.no,
>   52245@debbugs.gnu.org
> Date: Tue, 07 Dec 2021 17:30:19 +0100
> 
>     André> If I understand correctly, we're not discussing variables but commands.
>     André> Eli urges that it's import to keep C-\ as a toggle, and to add another
>     André> command to cycle the ring.  Seems fair to me, so that the old behaviour
>     André> is preserved.
> 
> We can keep C-\ as a toggle, 100% identical to how it works today. All
> people who have customized `default-input-method' to a single value
> have to do is nothing whatsoever.
> 
> If weʼre now saying we want a separate command that cycles through a
> list of input methods, then we might as well add a separate user
> option for that list (and then we could add *another* user option
> called input-method-toggle-or-cycle to indicate which command should
> be used for C-\)
> 
> I guess we could also have C-u C-u C-\ mean 'cycle', but thatʼs
> unergonomic.

The use case that I have in mind is this: even if the user customized
the list of input methods to include more than just one, there could
be situations where the user needs to use just one input method when
typing.  In such situations, it would be good to have a way of
toggling, like we do now, instead of cycling through all the other
methods.

Any reasonable solution to this use case would be welcome.  I'm
working with systems which allow you to do something like that, and it
frequently annoys me to have to cycle through all the keyboard layouts
I defined, just to be able to toggle between US English and some other
language.  So I wish that Emacs didn't have such an annoying problem,
if possible.