It depends on what the src things look like. You might be able to just call
ffap or some variant of it. Here is an example of the follow part that
works for a file and url for me.

#+BEGIN_SRC emacs-lisp
(org-link-set-parameters
 "rstack"
 :follow (lambda (path)
  (ffap (or (ffap-url-at-point)
    (ffap-file-at-point)))))
#+END_SRC

#+RESULTS:
| :follow | (lambda (path) (ffap (or (ffap-url-at-point)
(ffap-file-at-point)))) |


[[rstack:(("./screenshots/date-20-01-2022-time-10-36-54.png" . fade-out)
(src2 . fade-in) ("https://google.com" . fade-out))]]


John

-----------------------------------
Professor John Kitchin (he/him/his)
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu



On Thu, Jan 20, 2022 at 10:21 AM Matt Price <moptop99@gmail.com> wrote:

>
>
> On Wed, Jan 19, 2022 at 12:18 PM John Kitchin <jkitchin@andrew.cmu.edu>
> wrote:
>
>> I am not sure this is quite what you are looking for. You could use a
>> macro like this.
>>
>>
>>
>> {{{r-stack(((src1 . fade-out) (src2 . fade-in) (src3 . fade-out)))}}}
>>
>> * code :noexport:
>>
>> #+macro: r-stack (eval (r-stack $1))
>>
>> #+BEGIN_SRC emacs-lisp
>> (defun r-stack (src-alist)
>>   "SRC-alist will be a string containing a list of (src . data-fragment)
>> src is a url or filename
>> data-fragment
>>
>> Returns a string for export."
>>   (let ((src (read src-alist)))
>>     (format "#+BEGIN_EXPORT html
>> <div class=\"r-stack\">
>> %s
>> </div>
>> ,#+END_EXPORT"
>>    (string-join
>>     (cl-loop for (src . data-fragment) in src
>>      collect
>>      (format "  <img data-fragment=\"%s\" src=\"%s\"/>"
>>      data-fragment src))
>>     "\n"))))
>>
>>
>> (r-stack "((src1 . fade-out) (src2 . fade-in) (src3 . fade-out))")
>> #+END_SRC
>>
>> #+RESULTS:
>> : #+BEGIN_EXPORT html
>> : <div class="r-stack">
>> :   <img data-fragment="fade-out" src="src1"/>
>> :   <img data-fragment="fade-in" src="src2"/>
>> :   <img data-fragment="fade-out" src="src3"/>
>> : </div>
>> : #+END_EXPORT
>>
>> You could also make a link do that.
>>
>
> Huh.  This wasn't at all what I was thinking but it may be a much better
> way than I'd htought of.
>
> A link seems like it would be a great solution, especially if I could
> figure out how to get the :follow function to open an individual ~src~
> path. Would you use "looking-at" to get the right candidate, or can you
> think of a way to get completion candidates for a function that opens the
> file? I'm looking at your eamples in
> https://kitchingroup.cheme.cmu.edu/blog/2016/11/04/New-link-features-in-org-9
> but can't quite follow the code.
>
> Thank so mjch for this really interesting solution.
>
>>
>> John
>>
>> -----------------------------------
>> Professor John Kitchin (he/him/his)
>> Doherty Hall A207F
>> Department of Chemical Engineering
>> Carnegie Mellon University
>> Pittsburgh, PA 15213
>> 412-268-7803
>> @johnkitchin
>> http://kitchingroup.cheme.cmu.edu
>>
>>
>>
>> On Wed, Jan 19, 2022 at 9:42 AM Matt Price <moptop99@gmail.com> wrote:
>>
>>> I am trying ot figure out if I can create a simplified syntax for a
>>> particular special block in a derived HTML exporter.
>>>
>>> I'm trying to produce HTML like this:
>>>
>>> <div class="r-stack>  <img data-fragment="fade-out" src="...."/>  <img data-fragment="fade-in" src="..."/></div>
>>>
>>> The derived backend (org-re-reveal) already has an
>>>
>>> #+ATTR_REVEAL that an make the data-fragment attributes, so it's not hard to produce
>>>  the desired outpu:
>>>
>>> #+begin_r-stack
>>> #+ATTR_REVEAL: :frag appear[[imglink1]]
>>> #+ATTR_REVEAL: :frag appear[[imglink2]]#+end_r-stack
>>>
>>> However, I'd really like to add a less verbose syntax, like this:
>>>
>>> #+begin_r-stack :frag (appear appear)[[imglink1]][[imglink2]]#+end_r-stack
>>>
>>> My question is: will the exporter preserve information from these header-like arguments, and is
>>> there a mechanism I can use in a custom ~special-block-function~ to make use of htem?
>>>
>>> Thanks for your help as always!
>>>
>>> Matt
>>>
>>>