[AUCTeX] ffap-latex-mode to use kpsewhich

[Nicolas Richard]

Hello,

I often want or need to browse the code of the LaTeX packages I use, and
ideally using find-file-at-point on the name of a package should make
this easy. However, the default value of ffap-tex-path does not contain
the complete tree that TeX uses to find its files. Hence ffap usually
does not fine the file I'm looking for automagically.

I first tried setting that variable to the output of
$ kpsewhich -expand-path $(kpsewhich -show-path tex)
but that makes ffap very slow because there are many paths to search.

Instead of that, I now use the following replacement for
ffap-latex-mode, which is called by ffap when in latex-mode:

(defun ffap-latex-mode (name)
  "ffap function in latex buffers, using kpsewhich."
  (with-temp-buffer 
  ;; order is important : the first path found will be opened.
    (let ((ext '(".sty" ".cls" ".ltx" ".tex" ""))
          args)
      (setq args (mapcar (lambda (x) (concat name x)) ext))
      (funcall `(lambda () (call-process  "kpsewhich"  nil  t  nil ,@args)))
      (when (< (point-min) (point-max))
        (buffer-substring (goto-char (point-min)) (point-at-eol))))))

Despite the use of an external process this is rather fast, and proved
useful to me. I thought it might be useful to others too. It obviously
requires kpsewhich to be installed. I have
$ kpsewhich --version
kpathsea version 6.1.0


-- 
Nico.