fonts.fontconfig.defaultFonts.emoji does not work for some fonts

[justinlovinger]

Describe the bug
fonts.fontconfig.defaultFonts.emoji does not change the emoji font, whether or not fonts.fontconfig.penultimate.enable = true is set.

To Reproduce
Steps to reproduce the behavior:

1. Set fonts.fontconfig.defaultFonts.emoji = [ "DejaVu Sans Mono" ]
2. Run fc-match emoji to check font

Expected behavior
fc-match emoji should output "DejaVu Sans Mono".

Additional context
The font set with fonts.fontconfig.defaultFonts.emoji appears as the second to top font in fc-match -s emoji. If you add a ~/.fonts.conf with

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>
  <alias binding="strong">
    <family>emoji</family>
    <prefer>
      <family>DejaVu Sans Mono</family>
    </prefer>
  </alias>
</fontconfig>

the given font is still second from top in fc-match -s emoji.

With fonts.fontconfig.penultimate.enable = true, it looks like a different issue, with a similar result. With fonts.fontconfig.penultimate.enable = true, changing fonts.fontconfig.defaultFonts.emoji has no effect on fc-match -s emoji. It looks like emoji font is not set in fontconfig-penultimate.nix. With fonts.fontconfig.penultimate.enable = true, the above ~/.fonts.conf file does change the emoji font.

Notify maintainers

Metadata
Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

• system: "x86_64-linux"
• host os: Linux 5.4.35, NixOS, 20.03.1619.ab3adfe1c76 (Markhor)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3.4
• channels(root): "nixos-20.03.1619.ab3adfe1c76"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute:
# a list of nixos modules affected by the problem
module: fonts.fontconfig

[veprbl]

Relevant to #86601

[worldofpeace]

I've noted that it's with penultimate fontconfig where this option doesn't work, which we were aware of and why penultimate is no longer the default.

[justinlovinger]

I've noted that it's with penultimate fontconfig where this option doesn't work, which we were aware of and why penultimate is no longer the default.

Has fonts.fontconfig.defaultFonts.emoji been fixed without penultimate fontconfig, since this issue was made? When I made this issue, fonts.fontconfig.defaultFonts.emoji did not work, even without penultimate fontconfig. See my original description of this bug.

[worldofpeace]

I'm seeing that your test was fc-match -s emoji and we've actually tested that continuously since the option was added in https://github.com/NixOS/nixpkgs/blob/master/nixos/tests/fontconfig-default-fonts.nix#L31. We even install two emoji fonts to be sure https://github.com/NixOS/nixpkgs/blob/master/nixos/tests/fontconfig-default-fonts.nix#L13. Could you try with these fonts

fonts.fonts = with pkgs; [
      noto-fonts-emoji
      twitter-color-emoji
 ];

and

fonts.fontconfig.defaultFonts = {
   emoji = [ "Twitter Color Emoji" ];
 };

testing with fc-match emoji | grep '\"Twitter Color Emoji\"'?

[justinlovinger]

Your test works. However

fonts.fonts = with pkgs; [
  noto-fonts-emoji
];
fonts.fontconfig.defaultFonts = {
  emoji = [ "Noto Emoji" ];
};

with fc-match emoji | grep '\"Noto Emoji\"' and

fonts.fonts = with pkgs; [
  dejavu_fonts
  noto-fonts-emoji
];
fonts.fontconfig.defaultFonts = {
  emoji = [ "DejaVu Sans Mono" ];
};

with fc-match emoji | grep '\"DejaVu Sans Mono\"'

does not work. In both cases, the top emoji font is "Noto Color Emoji" instead of the configured default emoji.

[stale]

I marked this as stale due to inactivity. → More info

[jtojnar]

Only fonts that fontconfig knows as emoji fonts can be used: https://gitlab.freedesktop.org/fontconfig/fontconfig/-/blob/d263d4075ea90f7a296c4d65e69eea504906689e/conf.d/60-generic.conf#L25-47

nixpkgs/nixos/modules/config/fonts/fontconfig.nix

Lines 338 to 342 in 1275550

	Note that fontconfig matches color emoji fonts preferentially,
	so if you want to use a black and white font while having
	a color font installed (eg. Noto Color Emoji installed alongside
	Noto Emoji), fontconfig will still choose the color font even
	when it is later in the list.

[stale]

I marked this as stale due to inactivity. → More info

[maydayv7]

Still an issue

[stale]

I marked this as stale due to inactivity. → More info

[HenriAW]

+1