Emacs URI handler for recent GNOME.
~/.emacs:

(defun emacs-uri-handler (uri)
  "Handles emacs URIs in the form: emacs:///path/to/file#LINENUM"
  (let ((uri-struct (url-generic-parse-url (save-match-data (if (string-match "^'\\(.*\\)'$" uri) (match-string 1 uri) uri)))))
    (select-frame-set-input-focus (selected-frame))
    (find-file (decode-coding-string
		(apply 'unibyte-string
		       (string-to-list (url-unhex-string (url-filename uri-struct))))
		'utf-8))
    (let ((line (url-target uri-struct)))
      (if line (goto-line (string-to-number line))))))

[Desktop Entry]
Name=emacs url handler
Exec=/usr/bin/emacsclient --no-wait -e "(emacs-uri-handler \"%u\")"
MimeType=x-scheme-handler/emacs;
Type=Application
Terminal=false
Categories=Utility;Development;TextEditor;