Bug#849602: e: Bug#849602: firefox: font EmojiOne must be installed below /usr/share/fonts

[Jeremy Bicha]

Hi,

Apologies in advance for the lengthy response.

I have been working on color emoji support for Ubuntu and Debian. For
simplicity's sake, I'll refer to this as the GNOME feature although
it's more of a gtk3 feature I guess. The GNOME feature requires
fontconfig 2.12.6 (in DELAYED/5) and a suitable font (like
fonts-noto-color-emoji in the NEW queue) [1]

EmojiOneMozilla.ttf is not in the right format for use by the GNOME
feature. As far as I can tell, it's really only useful in Debian for
Firefox and Thunderbird  (or maybe something else built on top of
Mozilla). Therefore, I don't really see any practical benefit to
moving the font to /usr/share/fonts/.

Someone could package https://github.com/mozilla/emojione-colr but it
requires at least (node-)grunt-webfont which hasn't been packaged in
Debian yet.

Notably, the latest versions of the upstream Emoji One font (not the
build used by Mozilla) are only available under a license which
forbids modification and redistribution. Emoji One 2.2.7 is the final
freely licensed version and can be used for the GNOME feature (in
fact, it's the default included in Fedora 27). I'm a bit hesitant to
work on packaging it because it's unmaintained and requires several
NEW nodejs packages to really build it from source instead of using a
pre-compiled ttf.

There is a fork named Emoji Two which is slowly getting new emoji
added. Unfortunately, nobody has supplied a build system for Emoji Two
to produce the fonts we need. For the GNOME feature, it was suggested
that it could maybe be adapted to use the nototools system used by
fonts-noto-color-emoji. In that case, we wouldn't need to worry about
any NEW nodejs packages. Also, Mozilla hasn't switched to Emoji Two
yet either.

Firefox doesn't (yet?) support the GNOME feature for color emoji
fonts. So you would need 2 versions of Emoji One / Emoji Two, one for
Mozilla, one for GNOME.

Let me try to come to a conclusion:
1) Someone could package Mozilla's emojione-color, but its only known
use is for Firefox and Thunderbird.
2) The Firefox package could add a NEW binary package containing the
Mozilla font with a symlink to the thunderbird directory so that
thunderbird could depend on the new package. Since Thunderbird's
release schedule lags behind Firefox's a bit, it's possible that a
Firefox update would update the font in a way that wouldn't be
compatible with Thunderbird. Maybe I'm just imagining problems here,
but the file duplication issue seems so minimal to me, that I'm not
sure this is all that urgent either.

[1] https://community.ubuntu.com/t/try-color-emoji-in-18-04/1492

Thanks,
Jeremy Bicha