Tip of the Day

Although i don’t use it that much, i’ve had the following defun in my emacs config since i remember:

(defun totd ()
  (interactive)
  (random t) ;; seed with time-of-day
  (with-output-to-temp-buffer "*Tip of the day*"
    (let* ((commands (loop for s being the symbols
                           when (commandp s) collect s))
           (command (nth (random (length commands)) commands)))
      (princ
       (concat "Your tip for the day is:\\n"
               "========================\\n\\n"
               (describe-function command)
               "\\n\\nInvoke with:\\n\\n"
               (with-temp-buffer
                 (where-is command t)
                 (buffer-string)))))))

(Actually, i’ve tracked it down to a gnu.emacs.help thread dated 2001).

I’m sure you’ve guessed what it does. One possible use is to put the invocation (totd) at the end of your .emacs; but, as i tend to have emacs open for days, if not weeks, in a row, i prefer to just bind it to a keyboard shortcut and press it when i’m idling or thinking of a new post. I can also press the shortcut repeatedly until the random chosen command interests me.

Another possibility (if you don’t find it annoying), is to set a timer to get a periodic tip of the day, using something along the lines of:

(defvar jao-totd-timer (run-at-time "12:00am" (* 3600 24) 'totd))
(defun jao-cancel-totd
  (interactive)
  (cancel-timer jao-totd-timer))

Not that bad as a pastime

Emacsy OS X

Let me tell you how Emacs is more and more taking the center stage in my MacBook. In a previous post i explained how i set up Gnus as my mail (and of course, news) reader: i like Gnus so much that it quickly became my default. And, just in case you didn’t know, Emacs can be OS X’s default mail handler too: just go to Mail’s general preferences pane and set it–it’s that easy. (In the image, i’m setting fink’s carbon emacs package, but you’ll see there too CarbonEmacs or Aquamacs if you have them installed.) With that setting in place, OS X will dutifully use Gnus whenever a mail handler is requested (e.g., when following mailto: URLs, or when using ‘Send this page…’ in Safari).

Unlike Gnus, Emacs is not my default web browser, although i use w3m-el quite a bit (specially for technical manuals). So, every now and then i find myself seeing a page in Safari than i want to open in Emacs. Applescript to the rescue: fire up that ugly Script Editor and type this simple program:

property eclient : "/sw/bin/emacsclient -e "
tell application "Safari"
  set this_url to the URL of document 1
  do shell script eclient & \
          "'(w3m-browse-url \"" & this_url & "\")'"
	tell application "Emacs22" to activate
end tell

(changing the path to emacsclient and the name of your Emacs as needed). Of course, you’ll also need to start the Emacs server somewhere in your init files with (start-server), and to save the above script in ~/Library/Scripts/Applications/Safari. I’ve named it ‘Open in Emacs’, and it appears nicely as an entry in my FastScripts menu.

The last, and most interesting, bit is going in the opposite direction: accessing Safari (or any other Cocoa application, for that matter) from Emacs. Or, put in another one, executing AppleScript snippets within Emacs. One possibility is using Emacs’ shell-command in conjunction with OS X’s osascript, but there’s a sweeter way: the Elisp function do-applescript. For instance, the function jao-as-safari-doc below returns the URL and title of the active page in Safari:

 (defun jao-as-tell-app (app something)
   (let ((res (do-applescript (concat "tell application \""
                                      app "\" to " something))))
     ;; the string returned is quoted
     (substring res 1 -1)))

 (defun jao-as-safari-doc ()
   (interactive)
   (let ((url (jao-as-tell-app "Safari" 
                               "get the URL of document 1"))
         (name (jao-as-tell-app "Safari" 
                               "get the name of window 1")))
     (cons url name)))

This may seem a bit boring at first, but it can be put to good use: when i see a page worth taking a few notes, i open an org-mode buffer, and type a shortcut bound to the following function:

 (defun jao-org-insert-safari-link ()
   (interactive)
   (let ((l (jao-as-safari-doc)))
     (insert (org-make-link-string (car l) (cdr l)))
     (message "Link to %s inserted" (car l))))

and (minor) magic happens. I’m sure you can think of many other interesting uses of do-applescript, can’t you?

Emacs on the spotlight

I’ve been writing lately several snippets to improve the communication of Emacs with OS X. One of them is this quick and dirty mdfind mode that provides access, within an Emacs buffer, to the results of mdfind commands (the CLI to OS X’s Spotlight). Just put the above file somewhere in your load path, (require 'mdfind) in your init file and invoke M-x mdfind. You’ll be asked for a directory and a search string to perform in that directory. Under the rug, this shell command gets executed:

mdfind -onlyin directory query

The results (a file list) are collected in a special buffer in a new major mode (creatively dubbed mdfind-mode) that inherits from org-mode (this is Emacs 22; if you haven’t yet, take a look at org-mode: it is simply awesome), and that displays the files nicely fontified as links. See the comments at the beginning of mdfind.el for a list of available shortcuts that you can use to navigate and open (using OS X’s default handlers) the files in the list.

The functionality offered is right now limited and there’re many venues for improvement, so i guess i’ll keep adding features as i need them. But you’re encouraged to take this quick hack as an starting point to get the functionality that you deem important (and maybe share the results ). Or, alternatively, to leave your suggestions in the comments section.

An Emacs Client for Google Services

If you use Google’s Blogger, GCal and/or Reader, run-don’t-walk and grab the new Emacs Client For Google Services. Awesome!.

Yet another illustrated primer

This one, called Living in Emacs (PDF), covers the very basics of using Emacs as your working environment:

Getting started with Emacs requires navigating a steep learning curve. Our goal is to help you past the initially unfamiliar interface so that the power and utility of Emacs become apparent. Then you’ll be ready to explore further on your own, following up on the resources and tips at the end of the tutorial.

The 25-pages long tutorial closes with a good piece of advice:

Use Emacs. Live in it for a while, learn to love it a little bit. Like any complex program, it will take time for you to fully grok it, but the effort’s worthwhile: you’ll have become fluent in one of the most common UNIX programming utilities and picked up a fundamentally marketable skill to boot!

Worth a look if you’re just getting started.

Emacs-friendly Firefox

When i use Firefox, there’s nothing more annoying than editing a textarea. On a Mac, one has at least some Emacs-like shortcuts. Incomprehensibly, on GTK+ 2.0 Emacs shortcuts are no longer the default, and one has to put something like

include "/usr/share/themes/Emacs/gtk-2.0-key/gtkrc"

in ~/.gtkrc-2.0 to restore a minimum of sanity.

But still, what i really want is to edit those textareas using the real thing. I just stumbled upon the answer to my prayers: It’s All Text! is a Firefox add-on that provides an edit button on any text box. You click on it and, the first time, you’re asked for your editor of choice. As you’ll notice, the default option is wrong. Change it by /usr/bin/emacsclient (Emacs 21 users may use gnuclient instead), and don’t forget to start the Emacs server with (server-start) somewhere in your initialisation file.

Better, no?

Update: Well, things can be even better, as pointed out by Victor below. The Mozex extension lets you not only edit textareas, but also assign shortcuts, view sources or choose the editor for mailto URLs. For some reason, using just emacsclient -e '(compose-mail "%a" "%s")' didn’t work for me, so i’ve created a simple shell script, gnumail:

    #!/bin/sh
    exec emacsclient -e "(compose-mail \"$1\" \"$2\")"

and told Mozex to use it. Don’t forget to set the variable mail-user-agent to something reasonable (for instance, since i use Gnus, i’ve got (setq mail-user-agent 'gnus-user-agent) in my configuration files).

Thanks, Victor!

Tab shuffling in emacs-w3m

Emacs-w3m comes with an excellent tab mode, which you can enable with (setq w3m-use-tab t) in your .emacs. C-cC-t creates new tabs, C-cC-w closes them and you can navigate then with C-cC-[np], or, my favourite, using a tab list via C-cC-s (if you didn’t know about this one, give it a try: it’s very useful).

But i quickly find myself with lots of open tabs that happen to be in the wrong order, and i wanted something akin to Firefox’s ability to move and reorder them around. I didn’t find a way change a tab’s position in a vanilla emacs-w3m, but it wasn’t that difficult to cook up my own solution. This function:

(defun jao-w3m-switch-buffers (dist)
    (interactive "p")
    (let* ((dist (if (zerop dist) 1 dist))
           (current (current-buffer))
           (current-no (w3m-buffer-number current))
           (next (progn (w3m-next-buffer dist)
  			(current-buffer)))
           (next-no (w3m-buffer-number next)))
      (with-current-buffer current
        (rename-buffer "*w3m*<*>")
        (w3m-buffer-set-number next current-no)
	(w3m-buffer-set-number current next-no)
        (w3m-pack-buffer-numbers))
      (switch-to-buffer current)))

switches the current tab with the one to its right (cyclically), or to the n-th to its right if you provide a numerical argument (e.g. M-3). I’ve got this function bound to C-cC-f:

(define-key w3m-mode-map (kbd "C-cC-f") 'jao-w3m-switch-buffers)

Alternatively, one could define a function that moves the current tab to the right a number of times. We can take advantage of the above function for a quick hack:

(defun jao-w3m-move-buffer (dist)
  (interactive "p")
  (let ((dist (if (zerop dist) 1 dist))
    (while (> dist 0)
      (jao-w3m-switch-buffers 1)
      (setq dist (1- dist)))))

and bind that to a shortcut of your choice. There you go: easy tab shuffling.