Ihor Radchenko <yantar92@posteo.net> writes:

> "Christopher M. Miles" <numbchild@gmail.com> writes:
>
>> I'm the developer of Org mode package "org-link-beautify"
>> https://repo.or.cz/org-link-beautify.git . The package main theory
>> is to use org-link-parameters `:activate-func` to do link file preview
>> with generating thumbnail images or file content etc.
>>
>> But I found it's slow one some big Org file and slow on small Org file
>> when previewing has a lot.
>> ...
>> I can see the `org-mode` invoked `org-set-font-lock-defaults` soon when
>> `org-mode` enabled. I hope the link `:activate-func` function can be
>> called only on link elements which is VISIBLE (means unfolded subtrees
>> or similar). So org-mode don't need to render all buffer links at
>> beginning soon. Instead render them as needed as unfolded. (Maybe I read
>> source code without fully understand the code. If so, correct me,
>> thanks.)
>
> Emacs fontification, by default, only requests fontification of the text
> visible on screen. That's what LIMIT argument to `font-lock-keywords'
> MATCHER function is for. Org mode obeys LIMIT.
>
> If you are seeing fontification being requested for invisible part of
> buffer or parts of buffer outside screen, it is likely caused by some
> third-party package forcing the fontification.
>
> As usual, try emacs -Q + minimal set of loaded packages and see if you
> can reproduce the problem.

Ihor, Thanks for answering. Learned new stuff.

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