Set C Styles Automatically in Emacs (Shallow Thoughts)

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Fri, 30 Sep 2005

Set C Styles Automatically in Emacs

I just figured out a nifty emacs trick: how to set C styles automatically based on the location of the file I'm editing. That way, emacs will autoindent with the proper style whether I'm editing my own code, GIMP code, Linux kernel code, etc. assuming that I keep the source for these projects in predictable places.

First, define a derived mode for each style you might want to use. Each minor mode inherits from c-mode, but adds a c-set-style call. (Obviously, this assumes that the styles you want to use are already defined.)

(define-derived-mode gnu-c-mode c-mode "GNU C mode"
  (c-set-style "gnu"))
(define-derived-mode linux-c-mode c-mode "GNU C mode"
  (c-set-style "linux"))

Then add entries to your auto-mode-alist for each directory you want to treat specially:

(setq auto-mode-alist
[ . . . ]
      (cons '("gimp.*/" . gnu-c-mode)
      (cons '("linux-.*/" . linux-c-mode)
            auto-mode-alist) ) )

Your normal default style will still work for any files not matching the patterns specified in auto-mode-alist.

It might be possible to skip the step of defining derived modes by switching on the file's pathname in the C mode hook, but I've never figured out how to get the pathname of the file being loaded in any reliable way.

[ 13:42 Sep 30, 2005    More programming | permalink to this entry | ]

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