bug#70295: [PATCH] Allow preprocessing of previews

[Paul Nelson]

Hi Arash,

Yes, your suggestion sounds good.  One other quick thought: maybe it'd
be bad design to have an external variable like this that can only
really be used by one package at a time?  Would something like the
following be preferred?

(defvar preview-preprocess-functions nil
  "List of functions used to preprocess region before previewing.
The functions in this list will be called inside `preview-region' with
one argument which is a string.")

Then (dolist ...) inside preview-region.  Happy to adjust it either
way, let me know.

Thanks, best,

Paul