hideshow minor-mode

[Shiyuan]

Hi, 

   I want to turn-on the hide-show-minor-mode in a user-defined mymode. But it gives me the error: mymode doesn't support hide show minor mode. I have put  (require 'hideshow) at the beginning of mymode.el, and also 

(hs-minor-mode 1) in the body of the definition of the major mode, and after that 

I put (add-to-list 'hs-special-modes-alist '(mymode "{" "}" "/[*/]" nil nil)) in mymode.el. 

What else I should do to utilize the hs-minor-mode in mymode? Thanks. 

[Michael Heerdegen]

Enabling `hs-minor-mode' tests if `comment-start' and `comment-end' are
bound to something non-nil and fails otherwise. This happens even
before `hs-special-modes-alist' is handled. IMHO this doesn't make much
sense. FWIW, your minor-mode must bind `comment-start' and
`comment-end'.

If your mode doesn't have comments at all, you can bind these to a
regexp that always fails matching - like "\\=[^[:ascii:][:nonascii:]]".

Does that help?


Michael.

[Shiyuan]

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))

However, it doesn't work. Anything else I need to do? or is there other packages allow me to fold the source where the blocks are defined in this way?  Thanks. 

Shiyuan 

On Mon, Oct 15, 2012 at 1:04 PM, Michael Heerdegen <michael_...@web.de> wrote:

[Michael Heerdegen]

Shiyuan <gshy...@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.

[Shiyuan]

Michael, 

Thanks for the detailed reply. However, it doesn't work for me. I guess I make a mistake somewhere. Here is mymode.el: 

http://paste.lisp.org/display/132611

Thanks. 

On Mon, Oct 15, 2012 at 8:03 PM, Michael Heerdegen <michael_...@web.de> wrote:

Shiyuan <gshy...@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?

[Michael Heerdegen]

Hi again,

> Michael,
> Thanks for the detailed reply. However, it doesn't work for me. I
> guess I make a mistake somewhere. Here is mymode.el:
>
> http://paste.lisp.org/display/132611

Yes, there are two little errors.

First, you register your mode in `hs-special-modes-alist' after you
enable hs-minor-mode. That's too late, because hideshow then has
already initialized its stuff. Also, adding to `hs-special-modes-alist'
has to be done only once, and not every time mymode is enabled.

Second, you quoted mymode-forward-sexp-func in your quoted list:

| '(mymode "\\[begin]" "\\[end]" "#" 'mymode-forward-sexp-func nil))
^

That's not needed, remember, the quote before a list already prevents
evaluation of its members (you want to specify a symbol).

So, this should do the trick:

--8<---------------cut here---------------start------------->8---
(require 'hideshow)

(defun mymode-forward-sexp-func (arg)
"move over ARG balanced blocks; This is needed by hs-minor-mode"
(dotimes (number 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)))))))

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

(define-derived-mode mymode fundamental-mode
"mymode is a major mode for fun."
(setq mode-name "mymode")
(setq comment-start "#")
(setq comment-end "")
(hs-minor-mode 1))
--8<---------------cut here---------------end--------------->8---

Of course, that's all just for playing. If mymode was a major-mode
really to be used, you would leave it up to the user to call
`hs-minor-mode' e.g. in `mymode-hook', and not call it in the mode
definition.


Michael.

[Shiyuan]

Michael, 
That works. Thank you very much for guiding me into the world of Lisp.

Shiyuan  

On Tue, Oct 16, 2012 at 12:17 AM, Michael Heerdegen <michael_...@web.de> wrote:

Hi again,

> Michael,
> Thanks for the detailed reply. However, it doesn't work for me. I
> guess I make a mistake somewhere. Here is mymode.el:
>
> http://paste.lisp.org/display/132611

Yes, there are two little errors.

First, you register your mode in `hs-special-modes-alist' after you
enable hs-minor-mode.  That's too late, because hideshow then has
already initialized its stuff.  Also, adding to `hs-special-modes-alist'
has to be done only once, and not every time mymode is enabled.

Second, you quoted mymode-forward-sexp-func in your quoted list:

| '(mymode "\\[begin]" "\\[end]" "#"  'mymode-forward-sexp-func nil))
                                      ^

That's not needed, remember, the quote before a list already prevents
evaluation of its members (you want to specify a symbol).

So, this should do the trick:

--8<---------------cut here---------------start------------->8---
(require 'hideshow)

(defun mymode-forward-sexp-func (arg)
  "move over ARG balanced blocks; This is needed by hs-minor-mode"

  (dotimes (number 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)))))))

[Michael Heerdegen]

Shiyuan <gshy...@gmail.com> writes:

> That works.

Fine.

Maybe also have a look at folding.el, if you don't yet know it:

http://www.emacswiki.org/emacs/FoldingMode

It uses explicit markers, but therefore works out of the box in any
mode.


Regards,

Michael.