bug#43830: keyboard layout handling incompatible with rest of the OS

[Juri Linkov]

>> When your X xkb layout has some differences from an Emacs input method,
>> you need to adjust these mismatched keys, but this is not a big problem.
>
> It doesn't. With switching Emacs input methods between English and Russian
> I also get English '/' == Russian '.'. And so C-. in Russian input method
> works
> as C-/ in English, because it's the same physical key.
>
> Also, the same goes for many S-M-[digit] combinations, because characters
> on the digit row are often different in Russian layout. For example, S-M-6
> in
> English layout translates to M-^, `delete-indentation', but in Russian
> S-M-6
> becomes M-:, `eval-expression'. And so on.

All these problems are because of mismatch between your X layout and
your Emacs input method.  Emacs doesn't know the X layout, so you need
to define it in Emacs by adapting an existing input method,
or defining different keys manually.

> So, it is a good workaround that *mostly* works. But it doesn't solve the
> underlying issue. Which was successfully solved by other applications tens
> of years ago.

We already discussed this 10 years ago, and the conclusion was that
it would require too fundamental changes in how Emacs processes keystrokes.

If now you have new ideas about how this would be possible to implement
by keeping backward-compatibility of the existing design,
patches that demonstrate the ideas are welcome.