bug#72268: 31.0.50; Color emoji rendering

[Manuel Giraud via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

[...]

>> +** On OpenBSD, color Emoji are not supported.
>> +
>> +The system's FreeType library is not built with libpng support, so it
>> +can't display compressed colour emoji.  This is due to the fact that, on
>> +OpenBSD, libpng is provided through ports and that a base component
>> +cannot depend on that.
>
> First, we use US English spelling, so it should be "color", not
> "colour".

Ok, I'll change this one.

> More importantly, I don't think I understand the user-level meaning of
> this.  You say "compressed color Emoji", but what does that mean in
> practice?  Does it mean no font which supports color Emoji display
> will ever work on OpenBSD unless the FreeType library is rebuilt with
> PNG support?

I'm not sure myself.  "compressed color Emoji" is a copy-paste I made
from sthen@ own words.  Maybe it is refering to the PNG compression.

>If so (but then why say "compressed" above?), I think we should say so
>and include a bit more details about rebuilding FreeType on OpenBSD,
>like that Reddit discussion mentions.  OTOH, if some Emoji fonts can be
>used on OpenBSD, we should say that as well, and perhaps mention those
>fonts, if they are free.
>
> IOW, PROBLEMS is supposed to describe the problems and their solutions
> or workarounds in user-understandable terms, because that file is for
> Emacs users, not for Emacs developers.

I am wary about adding the described workaround because it modifies the
system's FreeType library for all applications.  And it does so by
relying on a ports (think a 3rd party package) of libpng.  I don't know
what would happen should someone remove the libpng package after having
applied this workaround.  Also, as explained in this recipe, it will be
gone after each system upgrade.

My idea was more to record this limitation into "etc/PROBLEMS" for
future reference.
-- 
Manuel Giraud