Re: yank-media: allow users to limit image types that can be inserted

[pinmacs <pinmacs@cas.cat>]

Eli, I think we can solve the three situations described with following 
algorithm/idea/inspiration [1]: through a configurable variable 
(yank-media-image-types ?). That would allow you to be able to select 
among all options (that for certain cases could be interesting, say 
"expert mode", I know what I am doing, verbose mode, etc.), and also, a 
way to filter out certain candidates based on what you need.

Making that variable equal to nil would be as it is now, and configuring 
it to "image/png", would only select one. I think others were thinking 
about a regex. As you wish, I only need some sort of filter, and I don't 
care too much on the detail of how it is configured.

[1]
#+begin_src emacs-lisp

(defun my/filter (lst allowed)
   "Filter elements from LST based on ALLOWED. If no match is found, 
return LST."
   (if (null allowed)
       lst
     (let ((filtered
            (delq nil (mapcar
                       (lambda (x)
                         (when
                             (member x allowed) x)) lst))))
       (if (null filtered) lst filtered))))

(defun my/select (lst allowed)
   (if (equal (length allowed) 1)
       allowed
     (completing-read
      "Several types available, choose one:"
      (my/filter lst allowed))))

(setq my/candidates '("image/png"
                       "image/pbm"
                       "image/xbm"
                       "image/xpm"
                       "image/jpeg"
                       "image/tiff"
                       "image/webp"))

;; 1. I only want png
(my/select my/candidates '("image/png"))
;; 2. I only want to select between png and/or jpeg
(my/select my/candidates '("image/png" "image/jpeg"))
;; 3. expert mode (just like it is now)
(my/select my/candidates nil)

;; example of how you would customize the variable
(setq yank-media-image-types '("image/png"))
#+end_src