Re: mm-coding-system-priorities

[Reiner Steib <4.uce.03.r.s@nurfuerspam.de>]

On Sat, Apr 12 2003, Lars Magne Ingebrigtsen wrote:

> Reiner Steib <4.uce.03.r.s@nurfuerspam.de> writes:
>> ,----[ M-x describe-coding-system utf-8 RET ]
>> | u -- utf-8 (alias of mule-utf-8)
>> `----
>>
>> Hm, does it even expect the original name of the coding-system and
>> *not* an alias?  If so, I think this should be made more clear in the
>> documentation.
>
> utf-8 is both a coding system and a charset, I think.

AFAICS, we need to distinguish between "base coding-system",
"aliased/subsidiary coding-system" and mime-charset.  utf-8 is both,
an "aliased/subsidiary coding-system" and a mime-charset, but not a
"base coding-system".  The problem is, that using utf-8 in
`mm-coding-system-priorities' has no effect[1] at all: You need to use
a non-aliased coding-system, as returned by `coding-system-base':

,----[ C-h f coding-system-base RET ]
| coding-system-base is a compiled Lisp function in `international/mule'.
| (coding-system-base CODING-SYSTEM)
| 
| Return the base coding system of CODING-SYSTEM.
| A base coding system is what made by `make-coding-system'.
| Any alias nor subsidiary coding systems are not base coding system.
`----

The doc-string of `mm-coding-system-priorities' doesn't mention this.
Even the default value for users with "current-language-environment =
Japanese" contains the bogus entry utf-8.

> (And I don't think it should matter whether you use the name or an
> alias.)

Changing `mm-sort-coding-systems-predicate' should achieve it (I have
committed this):

(defun mm-sort-coding-systems-predicate (a b)
  (let ((priorities
	 (mapcar (lambda (cs)
		   ;; Note: invalid entries are dropped silently
		   (and (coding-system-p cs)
			(coding-system-base cs)))
		 mm-coding-system-priorities)))
    (> (length (memq a priorities))
       (length (memq b priorities)))))

Bye, Reiner.

[1] See my test in <news:v965pyw1gv.fsf@marauder.physik.uni-ulm.de>
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