How to make a new mode based on c++-mode

[Helfer Thomas <helferthomas@free.fr>]

Hello,

I have created a parser which translates a file into C++ source code.
The initial file has a syntax very close to C++ with some additional
keywords.

I would like to provide an emacs mode for editing those files. 

For the moment I have written this :

----------------------------------------------------------------------

;;; -*-emacs-lisp-*-
;;; castfront.el --- ELisp package for making castfront related stuff
easier.

(provide 'castfront)

(defconst castfront-keywords
  (list
   (list
    "\\(@\\(Coef\\)\\)\\>"
    '(0 font-lock-warning-face prepend))
   ))

(defun castfront-font-lock ()
  "Turn on font-lock for CastFront keywords."
  (interactive)
  (if (functionp 'font-lock-add-keywords)
      (font-lock-add-keywords nil castfront-keywords)
    (let ((old (if (eq (car-safe font-lock-keywords) t)
		 (cdr font-lock-keywords)
	       font-lock-keywords)))
      (setq font-lock-keywords (append old castfront-keywords)))))

------------------------------------------------------------------------

I have then added the following line to my .emacs :

(defun my-castfront-font-lock-hook ()
    (if (or (eq major-mode 'c-mode) (eq major-mode 'c++-mode))
         (castfront-font-lock)))
(add-hook 'font-lock-mode-hook 'my-castfront-font-lock-hook)


This work pretty good. The only thing to do is to open my parsed file
with c++-mode. However I want more. I want them to have their own mode,
a mode that will automatically load the c++-mode to handle c++-construct
a that will add my keywords as above. How can I make it ?

Thank for help

Sincerely,

Helfer Thomas