+(defun select-safe-coding-system-interactively (from to codings unsafe
+ &optional rejected default)
+ "Select interactively a coding system for the region FROM ... TO.
+FROM can be a string, as in `write-region'.
+CODINGS is the list of base coding systems known to be safe for this region,
+ typically obtained with `find-coding-systems-region'.
+UNSAFE is a list of coding systems known to be unsafe for this region.
+REJECTED is a list of coding systems which were safe but for some reason
+ were not recommended in the particular context.
+DEFAULT is the coding system to use by default in the query."
+ ;; At first, if some defaults are unsafe, record at most 11
+ ;; problematic characters and their positions for them by turning
+ ;; (CODING ...)
+ ;; into
+ ;; ((CODING (POS . CHAR) (POS . CHAR) ...) ...)
+ (if unsafe
+ (setq unsafe
+ (mapcar #'(lambda (coding)
+ (cons coding
+ (if (stringp from)
+ (mapcar #'(lambda (pos)
+ (cons pos (aref from pos)))
+ (unencodable-char-position
+ 0 (length from) coding
+ 11 from))
+ (mapcar #'(lambda (pos)
+ (cons pos (char-after pos)))
+ (unencodable-char-position
+ from to coding 11)))))
+ unsafe)))
+
+ ;; Change each safe coding system to the corresponding
+ ;; mime-charset name if it is also a coding system. Such a name
+ ;; is more friendly to users.
+ (let ((l codings)
+ mime-charset)
+ (while l
+ (setq mime-charset (coding-system-get (car l) :mime-charset))
+ (if (and mime-charset (coding-system-p mime-charset)
+ (coding-system-equal (car l) mime-charset))
+ (setcar l mime-charset))
+ (setq l (cdr l))))
+
+ ;; Don't offer variations with locking shift, which you
+ ;; basically never want.
+ (let (l)
+ (dolist (elt codings (setq codings (nreverse l)))
+ (unless (or (eq 'coding-category-iso-7-else
+ (coding-system-category elt))
+ (eq 'coding-category-iso-8-else
+ (coding-system-category elt)))
+ (push elt l))))
+
+ ;; Remove raw-text, emacs-mule and no-conversion unless nothing
+ ;; else is available.
+ (setq codings
+ (or (delq 'raw-text
+ (delq 'emacs-mule
+ (delq 'no-conversion codings)))
+ '(raw-text emacs-mule no-conversion)))
+
+ (let ((window-configuration (current-window-configuration))
+ (bufname (buffer-name))
+ coding-system)
+ (save-excursion
+ ;; If some defaults are unsafe, make sure the offending
+ ;; buffer is displayed.
+ (when (and unsafe (not (stringp from)))
+ (pop-to-buffer bufname)
+ (goto-char (apply 'min (mapcar #'(lambda (x) (car (cadr x)))
+ unsafe))))
+ ;; Then ask users to select one from CODINGS while showing
+ ;; the reason why none of the defaults are not used.
+ (with-output-to-temp-buffer "*Warning*"
+ (with-current-buffer standard-output
+ (if (and (null rejected) (null unsafe))
+ (insert "No default coding systems to try for "
+ (if (stringp from)
+ (format "string \"%s\"." from)
+ (format "buffer `%s'." bufname)))
+ (insert
+ "These default coding systems were tried to encode"
+ (if (stringp from)
+ (concat " \"" (if (> (length from) 10)
+ (concat (substring from 0 10) "...\"")
+ (concat from "\"")))
+ (format " text\nin the buffer `%s'" bufname))
+ ":\n")
+ (let ((pos (point))
+ (fill-prefix " "))
+ (dolist (x (append rejected unsafe))
+ (princ " ") (princ (car x)))
+ (insert "\n")
+ (fill-region-as-paragraph pos (point)))
+ (when rejected
+ (insert "These safely encodes the target text,
+but it is not recommended for encoding text in this context,
+e.g., for sending an email message.\n ")
+ (dolist (x rejected)
+ (princ " ") (princ x))
+ (insert "\n"))
+ (when unsafe
+ (insert (if rejected "And the others"
+ "However, each of them")
+ " encountered these problematic characters:\n")
+ (dolist (coding unsafe)
+ (insert (format " %s:" (car coding)))
+ (let ((i 0)
+ (func1
+ #'(lambda (bufname pos)
+ (when (buffer-live-p (get-buffer bufname))
+ (pop-to-buffer bufname)
+ (goto-char pos))))
+ (func2
+ #'(lambda (bufname pos coding)
+ (when (buffer-live-p (get-buffer bufname))
+ (pop-to-buffer bufname)
+ (if (< (point) pos)
+ (goto-char pos)
+ (forward-char 1)
+ (search-unencodable-char coding)
+ (forward-char -1))))))
+ (dolist (elt (cdr coding))
+ (insert " ")
+ (if (stringp from)
+ (insert (if (< i 10) (cdr elt) "..."))
+ (if (< i 10)
+ (insert-text-button
+ (cdr elt)
+ :type 'help-xref
+ 'help-echo
+ "mouse-2, RET: jump to this character"
+ 'help-function func1
+ 'help-args (list bufname (car elt)))
+ (insert-text-button
+ "..."
+ :type 'help-xref
+ 'help-echo
+ "mouse-2, RET: next unencodable character"
+ 'help-function func2
+ 'help-args (list bufname (car elt)
+ (car coding)))))
+ (setq i (1+ i))))
+ (insert "\n"))
+ (insert "\
+The first problematic character is at point in the displayed buffer,\n"
+ (substitute-command-keys "\
+and \\[universal-argument] \\[what-cursor-position] will give information about it.\n"))))
+ (insert "\nSelect \
+one of the following safe coding systems, or edit the buffer:\n")
+ (let ((pos (point))
+ (fill-prefix " "))
+ (dolist (x codings)
+ (princ " ") (princ x))
+ (insert "\n")
+ (fill-region-as-paragraph pos (point)))
+ (insert "Or specify any other coding system
+at the risk of losing the problematic characters.\n")))
+
+ ;; Read a coding system.
+ (setq coding-system
+ (read-coding-system
+ (format "Select coding system (default %s): " default)
+ default))
+ (setq last-coding-system-specified coding-system))
+
+ (kill-buffer "*Warning*")
+ (set-window-configuration window-configuration)
+ coding-system))
+