Save modes and properties on file basis

Question

Files can have the same type (the same extension) and still have different kinds of contents for which I have different preferences. For instance, some text files are in English and some in Swedish, and they need to have the Flyspell dictionary set differently. Mostly, I want auto-fill-mode to be on, but for some files I always want to have manual control over where line breaks happen. For some files I want visual-line-mode to be on, but for others I want to truncate-files. Hence, I find myself issuing commands for this and other configurations every time I edit a file for which my preferences differ from my default settings.

What I would like is to have Emacs save these properties (and possibly others that I specify) on a file basis, and set them automatically when I next open the file, a bit similarly to how save-place-mode saves the position in each file, and goes to that position the next time the file is opened. I don't want to put any magic file variable lines in the files (because I want them “clean” when others look at the files, perhaps not using Emacs).

I'm fine with implementing this myself, but before I do, I'd like to check: is there already something that I can use to accomplish what I want in a simple way that I haven't found or thought of? I've googled for it but haven't found anything.

Answer 1

You can create an association list that links file names to setup functions.

(defun english-setup ()
  (message "English setup."))

(defun swedish-latex-setup ()
  ;; (flyspell-prog-mode)
  (message "Swedish setup"))

(setq setup-functions-alist '(("english.txt" . english-setup)
                              ("swedish.tex" . swedish-latex-setup)))

Then create a function that you will call after visiting a file that sets up the buffer.

(defun language-setup ()
  (let ((list  (copy-alist setup-functions-alist)))
    (while list
      (when (string-equal (file-name-nondirectory (buffer-file-name))
                          (car (car list)))
        (funcall (cdr (car list))))
      (setq list (cdr list)))))

(add-hook 'find-file-hook 'language-setup)

Note that language-setup only compares filenames without the directory, you may want to change file-name-nondirectory to another file name function.