From: John Kitchin <jkitchin@andrew.cmu.edu>
To: Nicolas Goaziou <mail@nicolasgoaziou.fr>
Cc: "Somelauw ." <somelauw@gmail.com>,
"emacs-orgmode@gnu.org" <emacs-orgmode@gnu.org>
Subject: Re: Expose value-begin and value-end instead of just value in org-element API
Date: Sun, 25 Feb 2018 19:43:26 -0800 [thread overview]
Message-ID: <m28tbgju01.fsf@andrew.cmu.edu> (raw)
In-Reply-To: <87k1v6k2wt.fsf@nicolasgoaziou.fr>
Nicolas Goaziou writes:
> Hello,
>
> John Kitchin <jkitchin@andrew.cmu.edu> writes:
>
>> +1 on this.
>>
>> I also have some janky code to do things like go to the beginning/end of
>> the value in a src block. Here is my solution to mark the code in a src
>> block.
>>
>> (defun ob-ipython-mark-code ()
>> "Mark the code in the block."
>> (interactive)
>> (org-edit-special)
>> (let ((p0 (point-min))
>> (p1 (point-max)))
>> (goto-char p0)
>> (org-edit-src-exit)
>> (set-mark (point))
>> (goto-char (+ (point) (- p1 2)))))
>
> You get the beginning of the code of a source block with
>
> (org-with-point-at (org-element-property :post-affiliated element)
> (line-beginning-position 2))
>
> and its end with
>
> (org-with-point-at (org-element-property :end element)
> (line-beginning-position (- (org-element-property :post-blank element))))
>
Wow. I would not have guessed either one of these! Thanks for sharing
them. Is that documented somewhere? I gather that given something like
#+header: :var a=5
#+name: test
#+BEGIN_SRC ipython
print(a)
#+END_SRC
which parses like (from org-element-context):
(src-block
(:language "ipython" :switches nil :parameters nil :begin 362 :end 436 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :value "\nprint(a)\n\n" :post-blank 1 :post-affiliated 394 :header
(":var a=5")
:name "test" :parent nil))
In this:
:begin refers to the point at the beginning of the #+header line.
whereas
:post-affiliated is the point after all the "affiliated" header/name lines, i.e. the
beginning of #+BEGIN_SRC.
:end refers to the point where the end of the element is, which may
include blank lines.
:post-blank is the number of blank lines (including lines that are just
spaces) after the element.
is that the right interpretation?
For elements with a :contents-begin where does :post-affiliated come in?
> From there, you can easily construct something that doesn't rely on
> `org-edit-special'.
>
>>> I think it would be preferable to also expose the value by beginning and
>>> ending buffer positions for the following reasons:
>>> - Consistency with elements that expose contents-begin and contents-end.
>
> The point is terminal elements are not consistent with non-terminal
> ones, and should not be.
>
>>> - More powerful. In my evil-org plugin I want to be able to mark the value
>>> property of the org element at point (so the user can do stuff like easily
>>> copy the code of the current code block), but to do so I need the beginning
>>> and ending position in the buffer of "value". The org-element API does
>>> currently not provide clean way to retrieve these positions.
>
> See above. It is quite simple to extract this information from the parse
> tree.
Once you get the idea, maybe, but this approach seems specific to
src-blocks (maybe any block) where there are delimiting lines. It
doesn't work on all elements (which to be fair was not claimed). I think
the OP was interested in something more consistent, which I am
sympathetic to.
Some things aren't clear to me what should happen though, especially in
composite elements like tables and plain lists. E.g. To just select a
table without the affiliated lines, one can use :contents-begin and
:contents-end, once you get the table element (e.g. by walking up the
:parent chain if you are in a cell or row).
In the absence of a single way, maybe there could be a small number of
ways to do this? How many cases do you think there are?
- blocks (which have :value)
- composite elements (which have :contents-begin/end and/or non-nil :parents)
- regular elements (which have :contents-begin/end)
Are there any others?
>
>>> - It's usually more efficient to return the beginning and ending positions
>>> than to retrieve the substring that contains the value, which may require a
>>> large buffer partition to be copied.
>
> Efficiency is a moot point because you still need to store the value of
> the block. If you remove it, the parse tree is no longer an equivalent
> representation of the document.
I can see this argument, but I am still unclear on which elements need a
value, and which don't. For example, src-blocks have a value, but a
paragraph doesn't, nor do items in a plain list, at least from
(org-element-context).
I guess my confusion comes from these being different than what comes
out of (org-element-parse-buffer).
>
> Regards,
--
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
next prev parent reply other threads:[~2018-02-26 3:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-19 23:29 Expose value-begin and value-end instead of just value in org-element API Somelauw .
2018-02-20 19:59 ` John Kitchin
2018-02-21 11:17 ` Nicolas Goaziou
2018-02-21 21:13 ` Somelauw .
2018-02-26 3:43 ` John Kitchin [this message]
2018-02-26 10:05 ` Nicolas Goaziou
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