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

[Eli Zaretskii <eliz@gnu.org>]

> From: Ihor Radchenko <yantar92@posteo.net>
> Cc: visuweshm@gmail.com, pinmacs@cas.cat, rpluim@gmail.com, emacs-devel@gnu.org
> Date: Mon, 28 Oct 2024 18:39:02 +0000
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Examine the available TARGETS, then bind
> > yank-media--registered-handlers to the appropriate value when invoking
> > yank-media.
> 
> I am surprised that you are suggesting to bind an internal variable that
> does not even have a documented format. Moreover, it is even
> deliberately hidden behind `yank-media-handler' wrapper.

This is all very new, and has yet to be tested by the relevant use
cases.  The initial implementation was basically for a single
platform, and thus is from my POV heavily skewed towards that single
platform.  Thus, I don't see the fact that some variable was deemed as
internal by the original implementor as something we cannot change if
we decide it's useful for applications.

In general, how to control which MIME types are used or presented to
users was not part of the original implementation and AFAIR was never
discussed.  The code we have basically assumes that all the MIME types
are relevant and could/should be used in any order.  Based on what I
see on various platforms with many different applications that support
the clipboard, I think this is quite naïve, so we must extend what we
have to support more control, and that might legitimately call for
reassessment of the internal vs public knobs.