R – A ‘hello world’ example for a major mode in Emacs


Can anyone provide me with a hello world example for a major mode in emacs?
I guess it's a beginner question, still I really like to write a major mode, both to learn emacs and elisp, as to be able to use customization to the fullest.

What I have done so far (and is working) :

  • wrote a file sample-mode.el and put it in a lisp dir
  • called in .emacs (require 'sample-mode)
  • wrote some defuns in it, and provided it at the end (provide 'sample-mode)

But still it doesn't seem to be activated, I cannot call it with M-sample-mode.

So how to do that? And can anyone provide me with a very very simple Hello World like working sample?

Best Solution

Ok, after some more googling I am at least one step furhter :

(define-derived-mode sample-mode ...) 

since the providing isn't defining the mode as I thought first.. This I found on :


A very very nice site for emacs-lovers.

With the help of that : I have made a HelloWorld example myself now : It's a (as small as possible) Csharp mode. I have used Euler1 as example rather than HelloWorld. The files you need to know about are :

  • the file the mode will be applied on Euler1.cs
  • the .emacs
  • and of course the mode itself

Since a pic is worth, at least a bunch of words : all files on 1 screen :

alt text

But since this nice pic seems to disappear half the time (anyone a clue? Open in new tab always brings it on, and the url is ok) some words too :-) :

  1. The mode : cs-mode.el

    (setq myKeywords 
     '(("WriteLine" . font-lock-function-name-face)
    . font-lock-constant-face)))
    (define-derived-mode cs-mode fundamental-mode
      (setq font-lock-defaults '(myKeywords)))
    (provide 'cs-mode)
  2. The .emacs, that makes the .cs files open in the right mode :

;; cs
(require 'cs-mode)
(add-to-list 'auto-mode-alist '("\\.cs\\'" . cs-mode))

And thats all : the cs-code itself is useless her, cause it won't show the effect of coloring the key-words. To see that see the pic, or open the pic in another tab/window.

Cheers, ph

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