Local things in Emacs

This is just a small note, since this have bugged me for a while. Basically, I have lots of extra key bindings running around in my Emacs configuration. Now, I use local-set-key for many of these. The problem is I hadn’t actually read the documentation for local-set-key enough.

One example that annoyed me was this: I had some local key bindings for RSpec buffers, that differed from the regular Ruby buffers. My RSpec minor mode still uses the ruby-mode-map though. My assumption was that local-set-key did things exactly as all other things with “local” in their name, namely doing a buffer local modification only. I finally found out that this wasn’t the case. Instead, when the RSpec minor mode was loaded for the first time, it ended up modifying the ruby-mode-map with its key bindings, which were then visible for all other Ruby buffers. Ouch.

So, if you use local-set-key, make sure you actually want to set that key in the current mode map, instead of only for the current buffer.

As far as I know, there is no way to set a real buffer local key binding without some acrobatics that unsets and resets the keys manually. I ended up solving my problem with the RSpec minor mode to having it clone the Ruby mode map and have its own mode map. Not an ideal solution, but it works for now.

How large is your .emacs?

I’ve been reading lots of blogs and opinions about emacs the last few days. What strikes me is all of these people who brag about how large their .emacs files have become. So let me make this very clear:

If your .emacs file is longer than a page YOU ARE DOING IT WRONG.

Why? Well. Unless you are a casual Emacs user, your .emacs should not be regarded as a configuration file. Rather, the .emacs file is actually the entry point to the source repository of your own version of Emacs. In effect, when you configure Emacs you create a fork, which has it’s own source that you need to maintain. This is not configuration. This is programming and you should approach it like you do all programming. What does that mean? Modularization. Clean code. Code comments. Source control. Tests. But modularization and source control are the ones that are most important for my Emacs configuration. I have loads of files in ~/emacs and every kind of extension I do has it’s own kind of file or directory to put it in. The ~/emacs directory is checked out from source control, and has got customizations for different platforms. That’s why my .emacs file is 4-5 lines long. Two for setting customizations that are specific to this computer, and the rest to load the stuff inside of ~/emacs. And that’s all.

So how do you handle modularization of Emacs Lisp code? This won’t be a tutorial. Just a few advices that might make things easier.

In no specific order:

  • (load “file.el”) will allow you to just load another file.
  • (require ‘cl) will give you lots of nice functionality from Common Lisp
  • I recommend you have one place where you add all your load paths. Mine look something like this:
    (labels ((add-path (p)
    (add-to-list 'load-path
    (concat emacs-root p))))
    (add-path "emacs/jde/lisp")
    (add-path "emacs/nxml")
    (add-path "emacs/own") ;; Personal elisp code
    (add-path "emacs/lisp") ;; Various elisp code, just dumped here
  • Why do it like this? Well, it gives you an easier way to add full paths to your load path without repeating lots of stuff. This depends on you defining emacs-root somewhere – do define it, it can be highly useful.
  • Set custom-file. (The custom-file is the file where Emacs saves customizations. If you don’t set a specific file for this, you will end up getting all customizations saved into .emacs which you really don’t want.) The code for this is simple. Just do (setq custom-file “the-file-name.el”)
  • Use hooks and advice liberally. They allow you to attach new functionality without monkey patching.
  • If you ever edit XML, NEVER use Emacs builtin XML editor. Instead download the excellent NXML package.
  • Learn how to use Info and customizations
  • Use Ido mode

Feel free to add other good advice in the comments. These were just a small smattering of stuff I like and which helps your environment quite seriously. But the most important part is the whole thing about keeping your .emacs extremely small!

Addendum: As Phil just pointed out (and which was part of my plan from the beginning) is that Autoloads should be used as much as possible. Also, make sure to bytecompile as much as possible.

Emacs Inferior mode for the Io language

For anyone who like the Io language and work with Emacs, here is a small Inferior mode for Emacs and Io.
It’s adapted from the Ruby Inferior mode. Download it here. To use it, just do “(require ‘inf-io)” and then M-x run-io.


nXML in earnest

So, for various undisclosed reasons it’s time to start seriously hacking XML. Now, the end artifact of this will be one of the few situations where XML is actually justified and makes this process better.

Of course, Emacs is a must for this challenge. I wouldn’t even try doing it without a real editor. Now, the undisputed king of XML in Emacs is nXML-mode. I want it everywhere. So the first step is to bring out Trang and convert all DTD’s into RelaxNG. Then edit schemas.xml and we’re running. Well, except for the simple fact that Emacs refuses to load anything else than xml-mode automatically. That sucks.

So after lots of looking, it seems there is a new magic-mode-alist that can look at the beginning of a buffer and “magically” decide what kind of buffer we’re dealing with. For some reason this behavior overrides my carefully laid out auto-mode-alist. Well. The solution for all you people is simple. Just add this snippet late in your loading process:

(setq magic-mode-alist
(cons '("<\\?xml " . nxml-mode)
(fset 'xml-mode 'nxml-mode)

An Emacs diversion: Font sizes

After a few weeks of very intense JRuby-OpenSSL hacking, I felt the need to do something different, so I’ve spent a few hours with my slightly rusty Emacs Lisp skills, trying to fix something that I really need. Namely, control over font-size and fonts in Emacs, on Linux. I want it inside Emacs and customizable by EL. To my surprise I couldn’t find anything like that anywhere.

For me personally, it’s necessary when presenting, since I usually code with a small font in Emacs, the code will be totally unreadable when presenting. And since I don’t have a fancy MacBook Pro, I need to be able to zoom in and out inside Emacs.

Presto, it wasn’t easy, but I’ve managed it. For some reason, font handling seems quite backward in Emacs. I had to extract the current font, and then split it and join the new array together again. Not neat and my way of doing it is not the best. But, for your pleasure, here is the code to do it, and also some code that establishes a font ring of the standard fonts in different sizes that can be walked through:

(defun inc-font-size ()
(let* ((current-font (cdr (assoc 'font (frame-parameters))))
(splitted (split-string current-font "-"))
(new-size (+ (string-to-number (nth 7 splitted)) 1))
(new-font (concat (nth 0 splitted) "-"
(nth 1 splitted) "-"
(nth 2 splitted) "-"
(nth 3 splitted) "-"
(nth 4 splitted) "-"
(nth 5 splitted) "-"
(nth 6 splitted) "-"
(number-to-string new-size) "-*-"
(nth 9 splitted) "-"
(nth 10 splitted) "-"
(nth 11 splitted) "-*-"
(nth 13 splitted))))
(if (> (length splitted) 14)
(dotimes (n (- (length splitted) 14))
(setq new-font (concat new-font "-" (nth (+ n 14) splitted)))))
(set-default-font new-font t)
(set-frame-font new-font t)))

(defun dec-font-size ()
(let* ((current-font (cdr (assoc 'font (frame-parameters))))
(splitted (split-string current-font "-"))
(new-size (- (string-to-number (nth 7 splitted)) 1))
(new-font (concat (nth 0 splitted) "-"
(nth 1 splitted) "-"
(nth 2 splitted) "-"
(nth 3 splitted) "-"
(nth 4 splitted) "-"
(nth 5 splitted) "-"
(nth 6 splitted) "-"
(number-to-string new-size) "-*-"
(nth 9 splitted) "-"
(nth 10 splitted) "-"
(nth 11 splitted) "-*-"
(nth 13 splitted))))
(if (> (length splitted) 14)
(dotimes (n (- (length splitted) 14))
(setq new-font (concat new-font "-" (nth (+ n 14) splitted)))))
(set-default-font new-font t)
(set-frame-font new-font t)))

(defvar *current-font-index* 0)

(defconst *font-ring* '(
"-urw-nimbus mono l-regular-r-normal--15-*-88-88-p-*-iso8859-1"
"-urw-nimbus mono l-regular-r-normal--17-*-88-88-p-*-iso8859-1"

(defun font-next ()
(let ((len (length *font-ring*))
(next-index (+ *current-font-index* 1)))
(if (= next-index len)
(setq next-index 0))
(setq *current-font-index* next-index)
(message (concat "setting " (nth *current-font-index* *font-ring*)))
(set-default-font (nth *current-font-index* *font-ring*) t)
(set-frame-font (nth *current-font-index* *font-ring*) t)))

(defun font-prev ()
(let ((len (length *font-ring*))
(next-index (- *current-font-index* 1)))
(if (= next-index 0)
(setq next-index (- len 1)))
(setq *current-font-index* next-index)
(set-default-font (nth *current-font-index* *font-ring*) t)
(set-frame-font (nth *current-font-index* *font-ring*) t)))

(defun font-current ()
(cdr (assoc 'font (frame-parameters))))

(defun font-set (ix)
(setq *current-font-index* ix)
(set-default-font (nth *current-font-index* *font-ring*) t)
(set-frame-font (nth *current-font-index* *font-ring*) t))

(provide 'fontize)

I also bound these methods to keys, like this:

(global-set-key [?\C-+] 'inc-font-size)
(global-set-key [?\C--] 'dec-font-size)
(global-set-key [?\M-+] 'font-next)
(global-set-key [?\M--] 'font-prev)

Hope this helps someone in the same situation.