Re: [Question] Custom parse tree filter

[Juan Manuel Macías]

Hi Nicolas,

Thank you very much for your excelent explanation, which has helped me
to learn new and valuable things.

I chose `headline' instead of `section' because in the scenario where I
want to apply those LaTeX groups I was looking for something like this:

{level 1 - group 1
    {level 2 group 1 + group 2
      {level 3 group 1 + group 2 + group 3
        {etc. }}}}

I have tested your function and it works fine when all headers are at
the same level, but with different levels the filter understands both
properties as `font' (?). Anyway, and only for practical purposes, and
because I think that my initial idea of 2 properties was uneconomical, I
have slightly modified your function with a single property
`:fontspec:'. Now, with a couple of marks and some regexp both the
\fontspec group and the one with \addfontfeature are extracted:

| :fontspec: font ! optional: features   | \fontspec{font}[features] |
|----------------------------------------+---------------------------|
| :fontspec: > features                  | \addfontfeature{features} |

then the variable `fontspec':

(let* ((font <font-string-obtained-via-regexp>)
      (fontfeature <fontfeature-string-obtained-via-regexp>)
(fontspec (cond (font font) (fontfeature fontfeature))))

is passed as an argument of `(funcall create-export-snippet ...)'

With a single property it works fine, although I have to test more...

Thak you very much!

Best regards,

Juan Manuel 

Nicolas Goaziou writes:

> Hello,
>
> Juan Manuel Macías <maciaschain@posteo.net> writes:
>
>> I am writing a custom parse tree filter that does the following (LaTeX
>> backend): if a heading has the ':font:' property, the content of that
>> heading is enclosed in a LaTeX group. If the property is ':fontfeature:',
>> then the content is enclosed in a different group. The filter works fine
>> when all the headings are at the same level. But with different levels,
>> it does not returns the expected result. It's evident that I'm doing
>> something catastrophically wrong :-). I wonder if anyone could put me on
>> the track of the origin of my error...
>>
>> Below, the offender function and a sample. Thanks in advance!
>
> I think you are operating at the wrong level. Higher level headlines
> contain lower level ones. I suggest to operate on sections instead.
>
> Also, using `org-element-interpret-data' is meh because you're operating
> at the parse tree level. You can insert export-snippet objects directly.
>
> Here's a proposal. This could be refactored, but you get the idea.
>
> (defun my-custom-filters/fontspec-headline (tree backend info)
>   (when (org-export-derived-backend-p backend 'latex)
>     (org-element-map tree 'section
>       (lambda (section)
>       (let ((font (org-export-get-node-property :FONT section t))
>               (fontfeature (org-export-get-node-property :FONTFEATURE section 
> t))
>               (create-export-snippet
>                ;; Create "latex" export-snippet with value V.
>                (lambda (v)
>                  (org-element-create 'export-snippet (list :back-end "latex" 
> :value v)))))
>           (cond
>            (font
>             (apply #'org-element-set-contents
>                    section
>                    (append (list (funcall create-export-snippet "%font 
> start\n"))
>                            (org-element-contents section)
>                            (list (funcall create-export-snippet "%font 
> end\n")))))
>          (fontfeature
>             (apply #'org-element-set-contents
>                    section
>                    (append (list (funcall create-export-snippet "%fontfeature 
> start\n"))
>                            (org-element-contents section)
>                            (list (funcall create-export-snippet "%fontfeature 
> end\n"))))))))
>       info)
>     tree))
>
> Also, when "org-cite-wip" is merged, you will be able to replace, e.g.,
>
>   (funcall create-export-snippet "%fontfeature start\n")
>
> with 
>
>   (org-export-raw-string "%fontfeature start\n")
>
> Regards,