Two Gnus tricks

I’ve added a couple of tweaks to my Gnus config lately. Nothing earth-shattering, but in both cases i was writing my own elisp for something that was already in there. So, i’ve thought i’d share them and, maybe, save you the trouble.

The first one is a quickie, and you probably know about it; but for some reason it took me ages to discover the correct configuration knob. When you reply a mail, emacs will use the value of user-mail-address to compose the From: header. One can also tweak gnus-posting-styles to change the address on a per group basis. But what i really wanted was to use the address in the mail i was replying to. I was writing a hook to that effect when i found the variable to set to accomplish it: message-alternative-mails. Here’s how i set it up:

    (setq message-alternative-emails
        (regexp-opt '("jao@gnu.org" "jaortega@goodmail.com" "jao@member.fsf.org")))

Worked like a charm. Now for the second one.

As i’ve mentioned in some post before, Gnus let’s you customise the summary line to your heart’s content by tweaking the variable gnus-summary-line-format. I normally use emacs in a maximized urxvt terminal, so i’ve got plenty of room in my summary lines. One thing i wanted to add is the message’s date in a) my time zone and b) human readable form (you know, something like ‘Today, 22:33′ or ‘Yesterday, 02:44′). I only knew two format directives showing a date (%d and %D), but neither fulfilled my wishes. So i started coding my own, but halfway discovered that Gnus already comes with a custom one, called user-date. You use it by inserting %&user-date; in the line format string. It works in conjunction with a configuration stored in gnus-user-date-format-alist, which contains a lists of pairs. The first member of the pair is the age of the message, the second a time format string for displaying the date of messages that old. You’ll understand it better with an example, taken from my current configuration:

    (setq gnus-user-date-format-alist
          '(((gnus-seconds-today) . "Today, %H:%M")
            ((+ 86400 (gnus-seconds-today)) . "Yesterday, %H:%M")
            (604800 . "%A %H:%M") ;;that's one week
            ((gnus-seconds-month) . "%A %d")
            ((gnus-seconds-year) . "%B %d")
            (t . "%B %d '%y"))) ;;this one is used when no other does match

    (setq gnus-summary-line-format
      (concat "%U%R %~(pad-right 2)t%* %uj %B%~(max-right 30)~(pad-right 30)n  "
              "%~(max-right 90)~(pad-right 90)s %-135=%&user-date;\n"))

I’ve copied my whole line format so that you can see, in addition, how i manage to keep things aligned in a frame around 180 columns wide. For details on the %uj directive, see this previous post.

Gmail envy

Although Gnus is my primary mail reader, there’s lots of things i like about Gmail (actually, Gmail is my primary inbox: Gnus reads mail from there). For instance, a little feature i love in Gmail is those markers that tell you whether you’re one of the direct recipients of a mail. When seeing a long list of mails in a mail list, i can quickly identify those with me explicitly in the To: or Cc: headers: chances are i’m slightly more interested in them.

In Gnus, one can customize the information shown in the message list by tweaking the variable gnus-summary-line-format. If you press C-h v gnus-summary-line-format to see all the formatting options, you’ll see there’s a lot of information to be shown, but not the one we want. But, as is always the case, we have a hook to extend the format to our hearts content: the %uX directive, where X is any letter you want. When Gnus sees that directive, it calls gnus-user-format-function-X, a function you must write returning a string that gets inserted in the summary line. So here we go: first i define a string with a regexp of my email addresses:

(defvar *jao-mails*
        "jao@foo\\.org\\|jao@baz\\.com\\|jao@grogle\\.com")

and then i function which returns a “»” if i’m the only recipient of the message, or a “~” if i’m in the To:, Cc: or BCc: headers among others:

(defun gnus-user-format-function-j (headers)
  (let ((to (gnus-extra-header 'To headers)))
    (if (string-match *jao-mails* to)
        (if (string-match "," to) "~" "»")
        (if (or (string-match *jao-mails*
                              (gnus-extra-header 'Cc headers))
                (string-match *jao-mails*
                              (gnus-extra-header 'BCc headers)))
            "~"
            " "))))

Then all that is left is using it in my gnus-summary-line-format:

(setq
 gnus-summary-line-format
 "%U%R %~(pad-right 2)t%* %uj %B%~(max-right 20)~(pad-right 20)n %s\n")

Notice the %uj doing the trick here. I’m sure you’ll come up with other uses to this extension mechanism, which, by the way, is also available for gnus-group-line-format, the variable governing how lines in the *Group* buffer are displayed.

Gnus and Google Groups

Eternal September notwithstanding, i have great daily fun reading a bunch of usenet groups, and their articles are sometimes a source of ideas for blogging. Of course, my usenet client is Gnus; but in a blog post one needs the Google Groups URL when mentioning and article. So, i just spent five minutes writing a snippet to go from Gnus to GG in a keystroke:

(defun jao-gnus-goto-google ()
  (interactive)
  (when (memq major-mode '(gnus-summary-mode gnus-article-mode))
    (when (eq major-mode 'gnus-article-mode)
      (gnus-article-show-summary))
    (let* ((article (gnus-summary-article-number))
           (header (gnus-summary-article-header article))
           (id (substring (mail-header-id header) 1 -1)))
      (browse-url
       (format "http://groups.google.com/groups?selm=%s" id)))))

As you see, i just check that i’m viewing a post, obtain the message identifier (trimming surrounding markup) and construct a query that looks up the corresponding GG article.

Talk about extensibility.