Re: hideshow minor-mode

[Michael Heerdegen <michael_heerdegen@web.de>]

Shiyuan <gshy2014@gmail.com> writes:

> Yes, that solves the problem. Now, I can turn on hs-minor-mode. 
>
> But actually the block in my major mode is defined by tags, not by
> braces/parentheses, like,
> [begin]
> This is the block.
> This is the block.
> [end]
>
> accord to the commentary in the hideshow.el file, we can define the
> BEGIN and the END of the block by regex, this is what I did,
>
> (add-to-list 'hs-special-modes-alist '(mymode "\\[begin]" "\\[end]"
> "#" nil nil))

Yes, that's not wrong.

> However, it doesn't work. Anything else I need to do?

I'm afraid you'll need to specify a FORWARD-SEXP-FUNC element in your
`hs-special-modes-alist' entry, since the default `forward-sexp'
function won't work for your mode.

This function must accept one argument ARG and implement moving over ARG
balanced blocks.

If you don't have something like that yet - I tried the following:

--8<---------------cut here---------------start------------->8---
(defun mymode-forward-sexp-func (arg)
  (dotimes (_ arg)
    (let ((counter 0))
      (catch 'done
        (while t
          (search-forward-regexp "\\[begin]\\|\\[end]")
          (setq counter (+ counter (if (looking-back "\\[begin]") 1 -1)))
          (when (= counter 0) (throw 'done t)))))))
--8<---------------cut here---------------end--------------->8---

It doesn't check for comments, dunno what else I forgot.  But,
if I then use

(add-to-list 'hs-special-modes-alist '(mymode "\\[begin]" "\\[end]"
"#" my-mode-forward-sexp-func))

folding worked for me in a test buffer using your syntax.

> or is there other packages allow me to fold the source where the
> blocks are defined in this way?

Fundamentally, hideshow is fine for that.  It's just the setup that
isn't trivial.  No doubt, there is room for improvement.


Regards,

Michael.