bug#60399: 30.0.50; Usage of `isearch-open-invisible-temporary' is not documented

[Juri Linkov <juri@linkov.net>]

> According to isearch.el source, one can use
> `isearch-open-invisible-temporary' to implement custom hidden text
> display during isearch. However, it is unclear what are the requirements
> for that function.
>
> From isearch source code, it appears that the function should accept two
> arguments: overlays and a flag to open/close the overlay:
>
>       ;; Some modes would want to open the overlays temporary during
>       ;; isearch in their own way, they should set the
>       ;; `isearch-open-invisible-temporary' to a function doing this.
>       (funcall  (overlay-get ov 'isearch-open-invisible-temporary)  ov nil)
>
> However, it appears that deleting the passed overlay is, in fact,
> prohibited. (manifested in
> https://orgmode.org/list/87pmc4smdg.fsf@fastmail.fm)
>
> Is there some detailed information about this feature available somewhere?

I don't know about this function more than you can read from source code,
but can find two mentions in (info "(elisp) Invisible Text") and
(info "(elisp) Overlay Properties").