Override/blacklist DejaVu emoji glyphs without making Emoji One Color the default font

[13rac1]

The Problem

The current readme recommends creating/modifying the user's fontconfig fonts.conf to make Emoji One Color the primary fallback font for sans-serif, serif and, monospace font families. This causes a number of issues including #1, #5, and #16. Ideally the DejaVu font family would stay the default and Emoji One Color would override/replace the emoji included in DejaVu Sans.

According to my tests in #16 (comment), only DejaVu Sans has the actual emoji characters which cause this problem:
which is what happens when the recommended fonts.conf is not installed.

A nice solution would be to blacklist the DejaVu Sans glyphs...

Blacklisting glyphs

There has been a number of requests for an option to "blacklist glyphs" or "create virtual fonts" in fontconfig over the years, but there is no current implementation AFAIK. (Too much detail follows, but this is a good place to keep the research.) 😉

Mixing arbitrary unicode ranges into a virtual font
might be needed when some fonts have just a few bad
characters [eg numbers], but normally mixing would be
by language.

Ideas on how to approach it [if not done already]?

src: https://lists.freedesktop.org/archives/fontconfig/2004-October/001045.html

Blacklisting glyphs in fonts has been a long standing wish for lots of
people, and the patch for fontconfig was even written once I think, but
it was never applied. Fontconfig people are just blaming the fonts with
all the different scripts. But as said before, it'll have to be
fontconfig which needs to be patched, since fonts won't do anything as
long as font substitution isn't available everywhere (and even then it
remains to be seen).

src: https://sourceforge.net/p/dejavu/mailman/message/9671050/

I remember that once upon a time the whole issue of making it possible
for FontConfig to blacklist glyphs from
fonts was discussed.

The idea was that it is easy and fast to write a few lines of XML into
a FontConfig .conf file while it is slow and
laborious to remove glyphs from a font.

Perhaps now is the time to actually implement this functionality in FontConfig?

src: https://lists.freedesktop.org/archives/fontconfig/2008-January/002847.html
Followed up by:

Sure, Pango totally uses fontconfig to determine if a font supports a
character. So this can completely be fixed in fontconfig. Someone
needs to go finish the patch and pass it through Keith I think.

src: https://lists.freedesktop.org/archives/fontconfig/2008-January/002850.html

• Finish patch for fontconfig to allow configuration to disable
  certain Unicode codepoints per font. The write such configuration for
  the crappy glyphs.

Pick whichever you prefer and just do it.

src: https://mail.gnome.org/archives/gtk-i18n-list/2007-December/msg00007.html

Solutions

As much fun as it would be to go down another rabbit hole, I don't have the time to patch fontconfig right now. Plus, backwards compatibility would still be an issue. The recommended solution is to remove the offending glyphs.

Actually IMO if the Latin glyph are crappy, removing them is the single
most correct solution.

src: https://lists.freedesktop.org/archives/fontconfig/2008-January/002846.html

This means a fork of DejaVu Sans is probably the answer. Any other ideas?! 😎

[13rac1]

Yes, still looks like the best solution. Microsoft and Apple probably ship emoji characters in a separate font for this reason.

Short term goal: DejaVu Sans without emoji to ship with this font.
Long term goal: a DejaVu Emoji font in a pull request.

Follow along here: https://github.com/eosrei/dejavu-fonts/tree/emoji

[13rac1]

Just found some emoji in DejaVu Serif and DejaVu Sans Mono. I need to fork the whole family! Yay.

[13rac1]

This font: https://github.com/eosrei/dejavu-fonts/commit/46ba8581cd599b4e4e247c5d3d19e02aa99f73fa with the following fonts.conf seems to work:

<fontconfig>
  <match>
    <test name="family"><string>sans-serif</string></test>
    <edit name="family" mode="prepend" binding="strong">
      <string>DejaVu Sans No Emoji</string>
      <string>Emoji One Color</string>
    </edit>
  </match>
  <match>
    <test name="family"><string>Apple Color Emoji</string></test>
    <edit name="family" mode="prepend" binding="strong">
      <string>Emoji One Color</string>
    </edit>
  </match>
  <match>
    <test name="family"><string>Segoe UI Emoji</string></test>
    <edit name="family" mode="prepend" binding="strong">
      <string>Emoji One Color</string>
    </edit>
  </match>
</fontconfig>

[13rac1]

I've found a much better solution to this issue: Bitstream Vera! It's the basis for DejaVu and doesn't include all of these characters needing to be overridden. Bitstream Vera is going to be the default install recommendation going forward. Noto can work if modified to remove a few emoji from the regular fonts which IMO should be moved to Noto Emoji I'll open on that project about it.

[qnub]

Have same view

[13rac1]

DejaVu is the default font family for Linux. My provided fontconfig is the solution for this.

[qnub]

fonts.config installed with this tdistributio give result from this screenshot.

[13rac1]

Please open a new issue with the following details:

• Linux distribution and version
• Firefox version
• The output from running the unit tests, both files are required: https://github.com/eosrei/emojione-color-font/tree/cc38faa4eb3cb04a44aa35221c913310fab49699/linux/tests