bug#56691: outline-minor-mode displays navigation arrow buttons as emojis

[Robert Pluim <rpluim@gmail.com>]

>>>>> On Fri, 29 Jul 2022 16:35:17 +0300, Eli Zaretskii <eliz@gnu.org> said:

    >> From: Robert Pluim <rpluim@gmail.com>
    >> Cc: Lars Ingebrigtsen <larsi@gnus.org>,  hello@paulwrankin.com,
    >> 56691@debbugs.gnu.org
    >> Date: Fri, 29 Jul 2022 14:48:01 +0200
    >> 
    Eli> (font-get (font-at 0 nil "😄") :family)
    Eli> => Symbola
    >> 
    >> There are dozens if not hundreds of fonts capable of displaying colour
    >> emoji.

    Eli> Really, hundreds?  Are you sure?  Dozens don't scare me, and I thought
    Eli> there are actually very few?

Iʼm constantly surprised by the number of colour emoji fonts. It may
not be hundreds, but itʼs a lot.

    >> Is it such a bad thing if we donʼt use the emoji when we could?

    Eli> You mean, by default assume color Emoji aren't supported?  That'd
    Eli> contradict what the documentation currently says, and is a strange
    Eli> thing to do in such features.

Weʼd need a reliable way of implementing this:

    Eli> (defun display-color-emoji-p (&optional frame)

and I donʼt really like the idea of using a fixed list (but Iʼm not
implementing it 😀

    Eli> Terminal emulators is a separate issue.  If we need to support that,
    Eli> we will have to let the user specify that.  (The current code doesn't
    Eli> support that, either, right?)

    >> Iʼve not been following, but I assume thereʼs a "damn the torpedoes,
    >> I know what Iʼm doing" option for this stuff.

    Eli> But the option's value is not a simple scalar, it is a list of
    Eli> preferences, and they are supposed to be used in the order listed when
    Eli> possible.  How do you reconcile that with "I know what I'm doing"?
    Eli> Are users supposed to know in advance, for every display they use,
    Eli> what are its capabilities?  And even if they do, are they supposed to
    Eli> configure Emacs to use the lowest common denominator of those
    Eli> displays?

Youʼre conflating the defaults with the configurability. By default we
should try to do the right thing, but allow users to override that
(but you know that).

Robert
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