Re: Recent documents: Emacs and GNOME integration

[Kevin Rodgers <ihs_4664@yahoo.com>]

Richard Stallman wrote:
> If the structure of the recent files list is simple enough,
> maybe it is easy to edit it correctly even without having the
> sophistication to parse xml.  Would someone like to take a look
> and try to write this?

I believe you are correct, but the spec is terribly imprecise:
there is no DTD or schema, no formal specification of the various
elements' content, numerous occurrences of "should", etc.  I sent
a message to the xdg@lists.freedesktop.org mailing list asking for
clarification, but it never even showed up in the archive
(http://lists.freedesktop.org/archives/xdg/).

So here's what I came up with based on the example in the spec:

(provide 'recent-files)

;; See 
http://standards.freedesktop.org/recent-file-spec/recent-file-spec-0.2.html#storage
(defconst recent-files-encoding "UTF-8")
(defconst recent-files-name "~/.recently-used")
(defconst recent-files-limit 500)

(require 'url-util)
(require 'mailcap)

(defun update-recent-file (file &optional mime-type timestamp private
				&rest groups)
   "Add or update FILE's entry in `recent-files-name'."
   (apply 'update-recent-file-item
	 (concat "file://" (mapconcat 'url-hexify-string
				      (split-string (expand-file-name file) "/")
				      "/"))
	 (or mime-type
	     (cdr (assoc (file-name-extension file t) mailcap-mime-extensions)))
	 (or timestamp
	     (format "%.f" (float-time)))
	 private
	 groups))			; (cons "Emacs" groups)

(defun update-recent-file-item (uri mime-type timestamp
				    &optional private &rest groups)
   ;; Replace "<", "&", and ">" by "&lt;", "&amp;", and "&gt;" resp.
   ;; in all string arguments (URI, MIME-TYPE, TIMESTAMP, and GROUPS)
   ;; but not the boolean argument (PRIVATE):
   (setq uri (url-insert-entities-in-string uri)
	mime-type (url-insert-entities-in-string mime-type)
	timestamp (url-insert-entities-in-string timestamp)
	groups (mapcar 'url-insert-entities-in-string groups))
   ;; Make sure recent-file is opened and saved in the correct encoding:
   (let* ((coding-system-for-read (intern (downcase recent-files-encoding)))
	 (coding-system-for-write coding-system-for-read)
	 (coding-system-require-warning t)
	 (recent-buffer (get-file-buffer recent-files-name)))
     (save-excursion
       (set-buffer (or recent-buffer (find-file-noselect 
recent-files-name)))
       (save-restriction
	(widen)
	(when (= (buffer-size) 0)
	  (goto-char (point-min))
	  (insert "<?xml version=\"1.0\" encoding=\""
		  recent-files-encoding
		  "\"?>")
	  (insert "\n" "<RecentFiles>")
	  (insert "\n" "</RecentFiles>"))
	(goto-char (point-min))
	(if (search-forward-regexp (concat "<URI>" (regexp-quote uri) "</URI>")
				   nil t)
	    ;; then: Per the spec, only update the timestamp and add new groups:
	    (progn
	      (search-forward-regexp "<Timestamp>\\(.*\\)</Timestamp>")
	      (replace-match timestamp t t nil 1)
	      (goto-char (match-end 0))	; end-of-line
	      (when groups
		(let (group-start group-end)
		  (if (looking-at "\n*<Groups>")
		      (progn
			(setq group-start (match-end 0))
			(setq group-end (search-forward-regexp "</Groups>")))
		    (insert "\n" "<Groups>")
		    (setq group-start (point))
		    (insert "\n" "</Groups>")
		    (setq group-end (point-marker)))
		  (goto-char group-start)
		  (mapc (lambda (group)
			  (unless (save-excursion
				    (search-forward-regexp
				     (concat "<Group>"
					     (regexp-quote group)
					     "</Group>")
				     nil group-end))
			    (insert "\n" "<Group>" group "</Group>")))
			groups))))
	  ;; else: Insert the new item:
	  (search-forward "</RecentFiles>")
	  (goto-char (match-beginning 0))
	  (insert "<RecentItem>")
	  (insert "\n" "<URI>" uri "</URI>"
		  "\n" "<Mime-Type>" mime-type "</Mime-Type>"
		  "\n" "<Timestamp>" timestamp "</Timestamp>")
	  (when groups
	    (insert "\n" "<Groups>")
	    (mapc (lambda (group)
		    (insert "\n" "<Group>" group "</Group>"))
		  groups)
	    (insert "\n" "</Groups>"))
	  (when private
	    (insert "\n" "<Private/>"))
	  (insert "\n" "</RecentItem>" "\n"))
	(save-buffer))
       (or recent-buffer (kill-buffer (current-buffer))))))

-- 
Kevin