Use Enriched mode in etc/HELLO to keep charset information

This allows to encode HELLO in UTF-8, thus supporting the entire
repertory of Unicode, while still keeping the charset info where
that is important.  Suggested by Michael Welsh Duggan <mwd@md5i.com>.
* lisp/textmodes/enriched.el (enriched-translations): Add
translations for 'charset'.
(enriched-decode-charset, enriched-handle-charset-prop): New
functions.
* lisp/facemenu.el (facemenu-special-menu): Add sub-menu for
'charset' property.
(facemenu-set-charset): New function.
(facemenu-remove-special): Remove the 'charset' property as well.

* etc/NEWS: Announce the new feature of Enriched mode.
* etc/HELLO: Recode in UTF-8 and place under Enriched mode.

* doc/emacs/text.texi (Enriched Properties): Mention the support
for 'charset'.

1 files changed, 18 insertions, 1 deletions

diff --git a/lisp/textmodes/enriched.el b/lisp/textmodes/enriched.el
index b9d247132dc..6b4c44a39e7 100644
--- a/lisp/textmodes/enriched.el
+++ b/lisp/textmodes/enriched.el
@@ -120,9 +120,11 @@ expression, which is evaluated to get the string to insert.")
     ;; The following are not part of the standard:
     (FUNCTION      (enriched-decode-foreground "x-color")
 		   (enriched-decode-background "x-bg-color")
-		   (enriched-decode-display-prop "x-display"))
+		   (enriched-decode-display-prop "x-display")
+                   (enriched-decode-charset "x-charset"))
     (read-only     (t           "x-read-only"))
     (display	   (nil		enriched-handle-display-prop))
+    (charset       (nil         enriched-handle-charset-prop))
     (unknown       (nil         format-annotate-value))
 ;   (font-size     (2           "bigger")       ; unimplemented
 ;		   (-2          "smaller"))
@@ -492,6 +494,21 @@ Return value is \(begin end name positive-p), or nil if none was found."
       (list from to 'face (list ':background color))
     (message "Warning: no color specified for <x-bg-color>")
     nil))
+
+(defun enriched-decode-charset (from to &optional cset)
+  (let ((cs (when (stringp cset)
+              (condition-case ()
+                  (car (read-from-string cset))
+                (error nil)))))
+    (unless cs
+      (message "Warning: invalid <x-charset> parameter %s" cset))
+    (list from to 'charset cs)))
+
+(defun enriched-handle-charset-prop (old new)
+  "Return a list of annotations for a change in the `charset' property."
+  (cons (and old (list (list "x-charset" (symbol-name old))))
+        (and new (list (list "x-charset" (symbol-name new))))))
+
 
 ;;; Handling the `display' property.