Re: Rmail and the raw-text coding system

[Mark Lillibridge <mark.lillibridge@hp.com>]

>  >> But AFAIK BABYL files use a single encoding for the whole file, and
>  >> since around Emacs-21.x that single encoding is supposed to be
>  >> emacs-mule (and I seem to remember that the BABYL file is supposed to
>  >> contain an annotation at the very beginning saying it's using
>  >> emacs-mule, if so).
>  
>  >     Arguably, it is a Rmail 22 bug that some BABYL files are encoded
>  > using raw-text.
>  
>  So you're saying that when Emacs-22 wrote those files, it used raw-text?
>  And that Emacs-22's Rmail reads those files properly?
>  And that Emacs-22's Rmail reads those files with raw-text?

yes, yes, and yes.

The Rmail 22 reading code uses:

    (unless (and coding-system
		 (coding-system-p coding-system))
      (setq coding-system
	    ;; Emacs 21.1 and later writes RMAIL files in emacs-mule, but
	    ;; earlier versions did that with the current buffer's encoding.
	    ;; So we want to favor detection of emacs-mule (whose normal
	    ;; priority is quite low), but still allow detection of other
	    ;; encodings if emacs-mule won't fit.  The call to
	    ;; detect-coding-with-priority below achieves that.
	    (car (detect-coding-with-priority
		  from to
		  '((coding-category-emacs-mule . emacs-mule))))))
    (unless (memq coding-system
		  '(undecided undecided-unix))
      (set-buffer-modified-p t)		; avoid locking when decoding
      (let ((buffer-undo-list t))
	(decode-coding-region from to coding-system))
      (setq coding-system last-coding-system-used))
    (set-buffer-modified-p modifiedp)
    (setq buffer-file-coding-system nil)
    (setq save-buffer-coding-system
	  (or coding-system 'undecided))))

If the file doesn't appear be valid emacs-mule, it tries raw-text and
succeeds (I think all files are valid raw-text).  On write, it ends up
using undecided-unix (see above), which uses raw-text because the buffer
cannot be written in emacs-mule validly for some reason.  Weird code
points?

    Thus, it both reads and writes using raw-text, preserving the
contents of the buffer so long as we don't upgrade to version 23.

- Mark