Re: [O] Structured links to headings with endless depth

[John Kitchin]

I don't think this should be in org-mode, it is still too fragile in many ways. 

For example, what if you have a colon in your headlines, e.g. "A chapter about Romans 15:13".  That will will mess up the suggested approach that splits on ":".

What if you have duplicate headlines in a hierarchy, how would you specify the nth one?

What if you have some convention to start at level 2 headlines? what would you do then?

What about include files?

What if you skip a level for some reason? What should the path look like then?

If you can't put custom_ids in, the next best solution for a static file might be to just jump to line numbers, and use a path-like link description. That will allow you to jump to a precise line with a link that looks like the path to that line.

[[file:some/file.org::43][1:2:3]]

Here is a function that will copy a link to the kill ring from the current point so it is easy to paste somewhere. That link will fold so it looks like 1:2:3 visually.

#+BEGIN_SRC emacs-lisp

(defun copy-link-with-path ()

  (interactive)

  (let ((line)

(fname (buffer-file-name))

(path-components '()))

    (save-excursion

      (org-back-to-heading)

      (setq line (line-number-at-pos))

      (push (nth 4 (org-heading-components)) path-components)

      (while (org-up-heading-safe)

(when (looking-at "*")

  (push (nth 4 (org-heading-components)) path-components)))

      (kill-new (format "[[file:%s::%s][%s]]"

fname

line

(s-join ":" path-components))))))

#+END_SRC

John

-----------------------------------
Professor John Kitchin 
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803

@johnkitchin
http://kitchingroup.cheme.cmu.edu

On Wed, Mar 14, 2018 at 3:10 AM, ST <address@hidden> wrote:

John, thank you for this solution!

I posted this question also here:

https://emacs.stackexchange.com/q/39384/18760

So if you wish, you may add your solution also there.

Somebody there, posted also a possible solution however the syntax is
pretty heavy:

[[org-heading:/path/to/file.org::*1:2:1]]

There is a workaround using links abbreviations, but still it is a
workaround...

I think this kind of linking is useful for many general cases. Christian
has expressed concerns that such links are easily breakable which is
true but only for documents that are in draft phase (or those which are
supposed to be restructured on regular basis - like ToDo lists). However
documents that has been published, like books or scientific papers, and
will no longer change - will benefit greatly from such linking option.
Imagine you have a scientific paper in your archive that you have
already published and removed write access from it in order not to
change it accidentally. You do want to reference certain
chapter:section:subsection from it in your new paper, which you are
currently writing, but creating a target <<chapter:section:subsection>>
in the old paper is no longer an option...

So may I ask as a feature request, to please add, following link type as
standard to the org-mode:

[[path/to/file.org::chapter:section:subsection:etc:optional target]]

- chapter/section/subsection could be also just numbers
- optional target target might be <<optional target target>>
- there is no need to add '*' (like
[[path/to/file.org::*chapter:section]] to the link, as ':' after '::'
imply that headings are referred.

Thank you!

On Tue, 2018-03-13 at 20:49 -0700, John Kitchin wrote:
> This is a tricky problem to generally solve. I think this does it
> approximately well enough. It is lightly tested and works by exactly
> matching headlines at subsequent levels. It will be problematic if you
> have headlines with : in them, and it assumes there is a level 1
> headline to start in.
>
>
> #+BEGIN_SRC emacs-lisp
> (defun xpath-follow (path)
>   (let* ((fields (split-string path "::"))
> (fname (car fields))
> (paths (split-string (cadr fields) ":"))
> (level 0)
> (current-point (point))
> cp hls n found)
>     (org-mark-ring-push)
>     (find-file fname)
>     (save-restriction
>       (while paths
> (setq cp (pop paths))
> (incf level)
> (setq hls (org-element-map (org-element-parse-buffer) 'headline
>     (lambda (hl)
>       (when (eq level (org-element-property :level hl))
> hl))))
> (setq n (-find-index (lambda (hl)
>        (string= cp (org-no-properties
>     (org-element-property :raw-value hl))))
>      hls))
> (if (not n)
>     (progn
>       (goto-char current-point)
>       (user-error "%s not found" cp))
>   (goto-char (org-element-property :begin (nth n hls)))
>   (org-narrow-to-subtree))))))
>
>
> (org-link-set-parameters
>  "xpath"
>  :follow 'xpath-follow)
> #+END_SRC
>
>
>
> John
>
> -----------------------------------
> Professor John Kitchin
> Doherty Hall A207F
> Department of Chemical Engineering
> Carnegie Mellon University
> Pittsburgh, PA 15213
> 412-268-7803
> @johnkitchin
> http://kitchingroup.cheme.cmu.edu
>
>
>
> On Mon, Mar 12, 2018 at 8:08 AM, ST <address@hidden> wrote:
>         Hello,
>
>         Ss Christian has pointed out - introduce a separate CUSTOM_ID
>         for text
>         with fixed structure and rather short verses is too heavy.
>
>         I do need to write a custom link type, if this use case is not
>         of common
>         interest for the orgmode community.
>
>         Thank you,
>
>
>         On Mon, 2018-03-12 at 15:10 +0100, Nicolas Goaziou wrote:
>         > Hello,
>         >
>         > ST <address@hidden> writes:
>         >
>         > > I'm not that experienced in writing in lisp. Is it
>         difficult to create
>         > > such custom link type? What is the closest link type that
>         you would
>         > > recommend to take as starting point (link on code, if
>         possible)?
>         >
>         > I'm not answering your question, but I suggest to use a
>         CUSTOM_ID
>         > instead. This is readily available.
>         >
>         > Regards,
>         >
>
>
>
>
>