Re: Bugfix for utf-8 XTerm/MinTTY and (set-input-meta-mode t)

[Eli Zaretskii]

> Date: Tue, 01 Jun 2021 17:28:59 +0000
> From: Max Mikhanosha <max.mikhanosha@protonmail.com>
> Cc: emacs-devel@gnu.org
> 
> > If these terminal emulators send M-x as 248 decimal, then how do they
> > send the Latin character ø, whose codepoint is 248 decimal?
> 
> Exactly the same 0xc3,0xb8. Its point of the encode meta-key in the 8th bit 
> mechanics, that you give up ability to type upper half of ASCII table 
> (128-255) instead using them to indicate meta key.  Its a life-safer for 
> those of us using vi, (on in Emacs case evil), otherwise sending meta keys as 
> Esc <key> really interferes with vi mode where Esc key is super-special..  
> You can still insert these characters by doing quoted-insert, ie C-v M-x and 
> it will insert ø

I see your point, but I don't think we can then accept this patch as
is.  The patch in effect _forces_ everyone to give up on being able to
type 8-bit Latin characters as soon as they configure keyboard
encoding to be UTF-8, right?  Or am I missing something?

> I also typed some stuff in Russian and nothing seem to be broke in UTF8 in 
> general.    If there is a concern that this patch can break something, maybe 
> one way forward is to rework it to add another meaning to meta mode flag, 
> like (set-input-meta-mode 'utf8), which would trigger what my patch is doing. 
>  But current behavior, where meta_key is checked before utf-8 decoding is 
> obviously a bug, as it produces garbage input by treating utf-8 encoding 
> itself as having meta modifiers.

If something like this is accepted, it must be an optional feature.
And I'm not yet sure we want it even then, it sounds like a kludge to
work around broken terminal emulator configuration and cater to other
editors.