Emacs on OS X

Prelude

In this article I’ll share with you a few tips and tricks about running Emacs under the Mac OS X operating system.

Installation

While Emacs is available for installation from various sources I personally recommend you to use the Emacs for Mac OS X binary distribution.

Installation via Homebrew is also a decent option, although it more time consuming.

After the installation you might want to wipe out the ancient Emacs 22 that ships with OS X by default(its presence will only cause headaches, trust me):

$ sudo rm /usr/bin/emacs
$ sudo rm -rf /usr/share/emacs

Keep in mind that the OS X updates will (unfortunately) bring Emacs 22 back from the dead, so you might consider altering your PATH instead.

Alternatively you can just create an alias in your shell and when you invoke emacs it will run the newly installed version:

$ alias emacs="/Applications/Emacs.app/Contents/MacOS/Emacs"

If you installed via Homebrew that path might look like this:

$ alias emacs="/usr/local/Cellar/emacs/24.2/Emacs.app/Contents/MacOS/Emacs -nw"

To make it permanent, if using bash, add that line to ~/.bash_profile. zsh users will want to update ~/.zshrc instead.

Full-screen support

The Homebrew Emacs formula includes a patch providing the M-x ns-toggle-fullscreen command for switching between normal and full-screen modes. It works well, but does not provide the typical OS X Lion full-screen app experience. In particular, it remains on the desktop, obscuring non-full-screen applications, rather than moving to its own space. For OS X Lion style fullscreen support have a look at this article.

Another option that you might want to explore is the maximizer utility that brings full-screen support for all Cocoa apps under Lion.

Keybindings

I heartily recommend you to remap your Caps Lock key to Control. This can be easily done via Preferences -> Keyboard -> Modifier Keys. If you’re using a laptop keyboard or the bluetooth keyboard you’ll definitely want to remap your right Option key to Control as well. No one can use effectively Emacs without a right Control key. Remapping it is a bit more involved and requires the use of the third-party utility KeyRemap4MacBook.

On a regular Mac keyboard you’ll probably want to map Command to Meta and Option to Super. On an external Windows keyboard you’ll want to map Command to Super and Option to Meta (on Windows keyboard the Command and Option keys are swapped). Add this to your init.el (or .emacs) file:

(setq mac-command-modifier 'super)
(setq mac-option-modifier 'meta)

If you often switch between your laptop keyboard and an external Windows keyboard (like me) you might want to define this helper command and bind it to some key combo (C-c w in the example):

(defun swap-meta-and-super ()
  "Swap the mapping of meta and super. Very useful for people using their Mac
with a Windows external keyboard from time to time."
  (interactive)
  (if (eq mac-command-modifier 'super)
      (progn
        (setq mac-command-modifier 'meta)
        (setq mac-option-modifier 'super)
        (message "Command is now bound to META and Option is bound to SUPER."))
    (progn
      (setq mac-command-modifier 'super)
      (setq mac-option-modifier 'meta)
      (message "Command is now bound to SUPER and Option is bound to META."))))

(global-set-key (kbd "C-c w") 'swap-meta-and-super)

Setting the PATH variable

Long story short - if you’re running Emacs from Spotlight (or any other launcher for that matter) your PATH and exec-path variables won’t be same as the ones in your shell (and that’s every nasty since you want be able to run some external programs from Emacs). The best way to handle this would be installing the package exec-path-from-shell by Steve Purcell.

Flyspell

For flyspell to work correctly you’ll need to install aspell plus a few dictionaries.

$ brew install aspell --lang=en

More goodies

If you want to spare yourself part of the headache of configuring Emacs on OS X and get a lot of extra firepower you might want to install Emacs Prelude - an enhanced Emacs 24.x configuration (developed by yours truly) that should make your experience with Emacs both more pleasant and more powerful.