Re: [O] How to define file-local preamble for graphviz dot?

[Vladimir Alexiev]

Vladimir Alexiev <vladimir.alexiev <at> ontotext.com> writes:

> I have a bunch of dot settings that I want to set globally. I hacked it like 
> this:
> (defadvice org-babel-expand-body:dot (before add-preamble (body params) 
> activate)

A better way to hack it is like that, using the header args :prologue and 
:epilogue

(eval-after-load "ob-dot"
  ' (progn
      (add-to-list 'org-babel-default-header-args:dot
                   '(:cache . "yes"))
      (add-to-list 'org-babel-default-header-args:dot
                   '(:prologue . "digraph g {
  rankdir=LR nodesep=0.2 ranksep=0.1 arrowsize=0.2
  node [fontname=courier fontsize=10 margin=\"0.02,0.01\" shape=box width=0.1 
height=0.1]
  edge [fontname=courier fontsize=8 labelfontname=courier labelfontsize=8]"))
      (add-to-list 'org-babel-default-header-args:dot
                   '(:epilogue . "}"))))

Unfortunately ob-dot doesn't interpret :prologue and :epilogue, so I adviced it:

(defadvice org-babel-expand-body:dot (before prologue-epilogue activate)
  "Interpret :prologue and :epilogue headers, like 
org-babel-expand-body:generic"
  (let ((pro (cdr-safe (assoc :prologue params)))
        (epi (cdr-safe (assoc :epilogue params))))
    (setq body (mapconcat #'identity
                          (append (when pro (list pro))
                                  (list body)
                                  (when epi (list epi)))
                          "\n"))))

Then in a particular file I can override the :prologue like so:

* Local Variables :noexport:
Local Variables:
eval: (setq-local org-babel-default-header-args:dot (cons '(:prologue . 
"digraph g {
  rankdir=LR nodesep=0.2 ranksep=0.3 arrowsize=0.1
  node [fontname=courier fontsize=8 margin=\"0.02,0.01\" shape=circle 
width=0.25 height=0.25 label=\"\"]
  edge [fontname=courier fontsize=8 labelfontname=courier labelfontsize=8]")
  (cl-remove :prologue org-babel-default-header-args:dot :key 'car :test 'eq)))
End:

This works, although it asks for confirmation every time the file is loaded.
Trying to do it with a code block:

#+BEGIN_SRC emacs-lisp :results silent :exports none
#+END_SRC

didn't work because that code is not executed automatically on export.