Re: Automatic recognition of some specific coding systems

[Eli Zaretskii <eliz@gnu.org>]

> From: Jürgen Hartmann <juergen_hartmann_@hotmail.com>
> Date: Tue, 24 Feb 2015 23:30:49 +0100
> 
> Consider an utf-8-unix encoded text file, meaningfully named
> utf-8-unix, that just contains the seven German special characters
> 
>    äöüßÄÖÜ   ("a"o"u"s"A"O"U)
> 
> in one single line followed by a newline character. Now we make two
> copies of this file and recode them to the other coding systems of
> interest:
> 
>    cp utf-8-unix latin-9-unix
>    recode ..l9 latin-9-unix
> 
>    cp utf-8-unix cp850-dos
>    recode ..pc cp850-dos
> 
> Visiting all tree files in an Emacs session that was freshly started
> by means of
> 
>    emacs -Q
> 
> - thank you for that important hint - yields a perfect recognition of
> the respective coding in the case of
> 
>    utf-8-unix
>    latin-9-unix   (recognized as latin-1-unix, equivalent here)
> 
> but the recognition fails tor the cp850-dos encoded file, as it is
> recognized as
> 
>    raw-text-dos
> 
> encoded and its contents is displayed as
> 
>    \204\224\201\341\216\231\232

That's true, but I see the same behavior in Emacs 22.3, if I invoke it
with "emacs -q" (lowercase 'q', since 22.x didn't support -Q), so
there's no change in behavior here.

> So my problem is to find a configuration of Emacs 24.4 that yields a
> correct automatic recognition of all tree coding systems
> 
>    utf-8-unix
>    latin-9-unix or
>    cp850-dos
> 
> when the files of the example above are visited. One has to keep in
> mind that this was perfectly possible with Emacs 22.3, as I just
> verified again.

How exactly did you verify with v22.3?  As I wrote above, I see the
same behavior in that version.  Did you invoke it with -q?  If not,
there are some customization of yours that modify the default
behavior, and the question becomes how to express the same
customizations in Emacs 24.