Optional argument in AuCTeX definition of environment

Question

I want to create a style file for the tcolorbox environment. I have the following:

(add-hook 'LaTeX-mode-hook
      (lambda ()
        (LaTeX-add-environments
         '("tcolorbox")
         ))
      )

However, I want Emacs to query for the optional [title=] parameter. How can I do that?

Answer 1

You should use the LaTeX-env-args function (see the documentation for more information). In your case:

(LaTeX-add-environments
   '("tcolorbox" LaTeX-env-args [TeX-arg-key-val (("title"))]))

There are some style files using this feature, you should check them out.

If you're writing a style file for the tcolorbox package, I strongly suggest you to submit it to the AUCTeX mailing list so it can be added upstream.

Answer 2

Using @giordano's suggestion, and examining other styles, I managed to do this:

(defun LaTeX-tcolorbox-env-item-opt-label (environment)
  "Insert a `tcolorbox` environment with an optional title."
  (LaTeX-insert-environment
   environment
   (let ((label (TeX-read-string "(Optional) Title: ")))
     (concat (unless (zerop (length label))
               (format "[title={%s}]" label))))))

(add-hook 'LaTeX-mode-hook
          (lambda ()
            (LaTeX-add-environments
             '("tcolorbox" LaTeX-tcolorbox-env-item-opt-label))))