RE: Automatic recognition of some specific coding systems

[Jürgen Hartmann]

@Eli Zaretskii: Thank you very much for your hint:

> Try this:
> 
>   (set-coding-system-priority 'utf-8 'cp850)
 
After doing this, the coding systems

   utf-8
   cp850

get correctly recognized, but

   latin-9-unix

gets wrongly recognized as cp850-unix encoded.

If I modify the lisp expression to

   (set-coding-system-priority 'utf-8 'latin-9)

it is utf-8 and latin-9 that are properly recognized while the test
file

   cp850-dos

gets detected as iso-latin-9-dos encoded.

If I pass all three coding systems to set-coding-system-priority,

   (set-coding-system-priority 'utf-8 'latin-9 'cp850)   or
   (set-coding-system-priority 'utf-8 'cp850 'latin-9)

it turns out that the function set-coding-system-priority ignores the third
coding system in these cases, because it belongs to the same coding
category as the coding system named in the second place. The source
code src/coding.c comments this in the lines 9972 and 9973 like this:

    /* Ignore this coding system because a coding system of the
       same category already had a higher priority.  */

So I fear that we can not use this function to establish the
simultaneous recognizability of all tree coding systems.

By the way, could you verify, that this is possible with Emacs 22.3
with the customization described in my previous post?

Juergen