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Themes

Basics

An Emacs theme is basically a set of faces. Emacs has a predefined set of core faces for basic things like comments, keywords, etc and by modifying those you can significantly alter the appearance of Emacs. Many modes add faces of their own as well. Prior to Emacs 24 the most popular way to incorporate custom color themes into Emacs was the color-theme package. While it usually got the job done it had some problems that we won’t be discussing here and more importantly - it’s a third-party package, that’s not part of Emacs proper. Emacs 24 comes with a selection of built-in themes that you can choose from, so you’re no longer bound to the default theme (which many find quite ugly). To choose a new theme just do a M-x load-theme (tab completion is available for the names of the available themes). At this point you can give the command a try with the tango theme. If you like a theme so much that you’d want to use it all the time you can put in your Emacs configuration (.emacs or init.el for instance) like this:

(load-theme 'theme-name t)

If you’d like to return to the default-theme just do a M-x disable-theme.

Create Custom Themes

Emacs 24 finally introduced a new standard way of dealing with color themes (based on Emacs’s built-in customize facility). While it doesn’t have a proper name (as far as I know) it’s commonly referred to as the deftheme facility, since deftheme is the name of the macro you’d use to create such a theme. ( deftheme has actually been around since Emacs 23, but it was heavily improved in Emacs 24 )

How do you create a deftheme theme? Quite simply actually - just do a “M-x customize-create-theme”. You’ll be presented with an UI prompting you for a theme name, description and faces. After you save the theme a file called name-theme.el will be written on your filesystem. Here’s its skeleton:

(deftheme demo
  "Demo theme")

(custom-theme-set-faces
 'demo
 ;;; list of custom faces
 )

(provide-theme 'demo)

There was also an online theme generator here, but it seems to be down at the moment.

If dislike customize, you can just have a look at the source code of the built-in tango (or any other) theme and use it as a reference.

Once you’ve created the new theme you’ll have to drop it in a folder that’s on the custom-theme-load-path. I’d suggest the following:

(add-to-list 'custom-theme-load-path "~/.emacs.d/themes")

If you’re an Emacs Prelude user you’re already covered. This folder exists and is automatically added to custom-theme-load-path by Prelude, so all you have to do is drop there the themes you’d want to try out.

You may find the rainbow-mode useful when developing color themes. If fontifies strings that represent color codes according to those colors. The mode is known to be a great addition to css-mode, but I find it very helpful with color theme development as well. It’s also included (and enabled) in Prelude by default.

The Emacs package manager package.el (formerly known as ELPA) is gaining a lot of popularity lately and the community Marmalade repository already houses a few Emacs 24 themes that you can install from there. If you’re developing a theme that you’d like to submit to Marmalade it’s imperative that the theme modifies the custom-theme-load-path in an autoload - otherwise it won’t be of much use. Add the following snippet (or something similar) before the provide-theme line if your custom theme:

;;;###autoload
(when load-file-name
  (add-to-list 'custom-theme-load-path
               (file-name-as-directory (file-name-directory load-file-name))))

I’d also advise you follow the proper naming convention name-theme.el so that it’s apparent that your theme is deftheme compatible.

Oh, and one more thing - porting themes from color-theme to deftheme is really simple (just have a look at the old and the new version of Zenburn in its repo), so you should really consider porting all the themes you maintain to deftheme.

Notable Themes

• Zenburn
• Solarized