Re: Code snippet for Message Sequence Diagram export

[Juan <Pechiar@computer.org>]

Dan,

Below is the final proposal for org-babel-mscgen.el.

Already sent form to assign@gnu.org, got no answer (I assume it is
OK).

I remade all of the code, so almost no traces from org-babel-ditaa.

On Mon, May 17, 2010 at 10:24:10PM -0300, Juan wrote:
> On Mon, May 17, 2010 at 07:04:14PM -0400, Dan Davison wrote:
> > Juan <Pechiar@computer.org> writes:
> > > Below goes code snippet using org-babel instead of org-export.

> > And a couple of little questions:
> >
> > - I think I'd prefer to get rid of the org-mscgen-path variable, and
> >   simply require that mscgen is on the user's $PATH. Is that OK or am I
> >   missing a reason for doing it differently?
>
> You're right. I'll get rid of it.

Done. Now mscgen must be accessible on exec-path.

> ...

> > - If you are feeling energetic, it would be really nice to check the
> >   exit code from the shell-command and use org-babel-error-notify if
> >   necessary
>
> I'll look into it.

Done. Now error messages from mscgen are passed to
org-babel-error-notify.

Just a question on style:

If you look at the '(unless' line below, I throw an elisp 'error' if
the user forgets to add an output file to the #+begin_src header.

Is this OK, or should I stick to org-babel-error-notify with a dummy
exit code?

Thanks & regards,
.j.

8<------------------------------------------------------------

;;; org-babel-mscgen.el --- org-babel functions for mscgen evaluation

;;; TODO insert license information
;;; Author: Juan Pechiar (juan@pechiar.com)

;;; Commentary:
;;
;; This software provides EMACS org-babel export support for message
;; sequence charts. The mscgen utility is used for processing the
;; sequence definition, and must therefore be installed in the system.
;;
;; Mscgen is available and documented at http://www.mcternan.me.uk/mscgen/index.html
;;
;; Example:
;;
;; #+begin_src mscgen :file example.png
;; msc {
;;  A,B;
;;  A -> B [ label = "send message" ];
;;  A <- B [ label = "get answer" ];
;; }
;; #+end_src

;;; Code:
(require 'org-babel)

(org-babel-add-interpreter "mscgen")

(add-to-list 'org-babel-tangle-langs '("mscgen" "mscgen"))

(defvar org-babel-default-header-args:mscgen
  '((:results . "file") (:exports . "results"))
  "Default arguments to use when evaluating a mscgen source block.")

(defun org-babel-expand-body:mscgen (body params &optional processed-params) body)

(defun org-babel-execute:mscgen (body params)
  "Execute a block of Mscgen code with org-babel.  This function is
called by `org-babel-execute-src-block'."
  (message "executing Mscgen source code block")
  (let* ((out-file (or (cdr (assoc :file params)) "output.png" ))
         exit-code
         (stderr
          (with-temp-buffer
            (insert body)
            (setq exit-code (org-babel-shell-command-on-region
                             (point-min) (point-max) (concat "mscgen -T png -o " out-file)
                             nil 'replace (current-buffer)))
            (buffer-string))))
    (unless (cdr (assoc :file params)) (setq stderr (concat stderr "\nERROR: no output file specified. Add \":file some_name.png\" to the src header" )) (error stderr))
    (if (> exit-code 0) (org-babel-error-notify exit-code stderr))
    out-file))

(defun org-babel-prep-session:mscgen (session params)
  (error "Mscgen does not support sessions"))

(provide 'org-babel-mscgen)
;;; org-babel-mscgen.el ends here