Avoiding double encoding in subject

[Reiner Steib <reinersteib+gmane@imap.cc>]

Hi,

when replying to an article who's subject contains an unknown (or
invalid) encoding...

| Newsgroups: gmane.test
| Archived-At: <http://permalink.gmane.org/gmane.test/3051>
| Message-ID: <v94px7cjcs.fsf@marauder.physik.uni-ulm.de>
| Subject: bogus or unknown charset in =?iso-8859-17?Q?=E4?= subject

-- i.e. the charset is unknown to (X)Emacs[1] -- and not present in
`mm-charset-synonym-alist', Gnus produces a subject like...

| Newsgroups: gmane.test
| Archived-At: <http://permalink.gmane.org/gmane.test/3052>
| Message-ID: <v9y7ujb39h.fsf@marauder.physik.uni-ulm.de>
| Subject: Re: bogus or unknown charset in =?us-ascii?Q?=3D=3Fiso-8859-17=3F?=
|  =?us-ascii?Q?Q=3F=3DE4=3F=3D?= subject

Bad.

I'm not sure how Gnus should handle this situation.  Some
possibilities:

(1) Gnus could (probably, I don't know if it is feasible to implement
    this) mark the Subject as "not decoded" and resend it "as is"
    without the double[2] us-ascii encoding.  Gnus also has to make
    sure that this mark survives when the article is saved to the
    drafts folder.

    Problem: If the given charset is really invalid rather than
    unknown (the user usually can't decide), Gnus will also produce an
    incorrect article.

(2) Gnus' decoder could replace the unknown/invalid characters with a
    replacement character ("?", U+FFFD = REPLACEMENT CHARACTER, ...).

    Problem: It's probably not possible to get the number of
    replacement characters right.

Other suggestions?

Bye, Reiner.

[1] This may happen when (X)Emacs is to old to support a newly
    introduced charset.
-- 
       ,,,
      (o o)
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