Use apple fonts as defaults for fontconfig users

local.conf

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
    <!-- pixel alignment rgba -->
    <!-- check it here http://www.lagom.nl/lcd-test/subpixel.php -->
    <match target="font">
        <edit name="rgba" mode="assign">
            <const>rgb</const>
        </edit>
    </match>
    <!-- end pixel alignment -->

    <!-- lcd filter specification -->
    <match target="font">
        <edit name="lcdfilter" mode="assign">
            <const>lcddefault</const>
        </edit>
    </match>
    <!-- end lcd filter specification -->

    <!-- disable auto hinting for bold fonts -->
    <match target="font">
        <test name="weight" compare="more">
            <const>medium</const>
        </test>
        <edit name="autohint" mode="assign">
            <bool>false</bool>
        </edit>
    </match>
    <!-- end disable auto hinting for bold fonts -->

    <!-- Map common aliases to case insensitive system aliases -->
    <match target="pattern">
        <test qual="any" name="family" compare="contains">
            <string>mono</string>
        </test>
        <edit name="family" mode="assign">
            <string>monospace</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family" compare="contains">
            <string>Mono</string>
        </test>
        <edit name="family" mode="assign">
            <string>monospace</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family" compare="contains">
            <string>Monospace</string>
        </test>
        <edit name="family" mode="assign">
            <string>monospace</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>Serif</string>
        </test>
        <edit name="family" mode="assign">
            <string>serif</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>Sans</string>
        </test>
        <edit name="family" mode="assign">
            <string>sans-serif</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>Sans Serif</string>
        </test>
        <edit name="family" mode="assign">
            <string>sans-serif</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>Sans-Serif</string>
        </test>
        <edit name="family" mode="assign">
            <string>sans-serif</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>Sans-serif</string>
        </test>
        <edit name="family" mode="assign">
            <string>sans-serif</string>
        </edit>
    </match>

    <!-- Well known fonts are given 'sans-serif' -->
    <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>Helvetica</string>
        </test>
        <edit name="family" mode="assign_replace">
            <string>sans-serif</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>Arial</string>
        </test>
        <edit name="family" mode="assign_replace">
            <string>sans-serif</string>
        </edit>
    </match>
        <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>Monaco</string>
        </test>
        <edit name="family" mode="assign_replace">
            <string>monospace</string>
        </edit>
    </match>

    <!-- Load per-user customization file, but don't complain if it doesn't exist -->
    <include ignore_missing="yes" prefix="xdg">fontconfig/fonts.conf</include>

    <!-- Load local customization files, but don't complain if there aren't any -->
    <include ignore_missing="yes">conf.d</include>
    <include ignore_missing="yes">local.conf</include>

    <!-- Map apple system aliases to "sans-serif" for web "system font" stack -->
    <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>-apple-system</string>
        </test>
        <edit name="family" mode="assign">
            <string>sans-serif</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family" compare="eq">
            <string>BlinkMacSystemFont</string>
        </test>
        <edit name="family" mode="assign">
            <string>sans-serif</string>
        </edit>
    </match>

    <!-- Prefer emoji font for all system aliases -->
    <alias>
        <family>monospace</family>
        <prefer>
            <family>emoji</family>
        </prefer>
    </alias>
    <alias>
        <family>sans-serif</family>
        <prefer>
            <family>emoji</family>
        </prefer>
    </alias>
    <alias>
        <family>serif</family>
        <prefer>
            <family>emoji</family>
        </prefer>
    </alias>

    <!-- THIS IS WHERE YOU DEFINE FONTS -->
    <match target="pattern">
        <test qual="any" name="family">
            <string>emoji</string>
        </test>
        <edit name="family" mode="prepend_first" binding="same">
            <string>Noto Color Emoji</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family">
            <string>sans-serif</string>
        </test>
        <edit name="family" mode="prepend_first" binding="same">
            <string>SF Pro Text</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family">
            <string>sans-serif</string>
        </test>
        <test qual="any" name="size" compare="more">
            <double>19</double>
        </test>
        <edit name="family" mode="prepend_first" binding="same">
            <string>SF Pro Display</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family">
            <string>serif</string>
        </test>
        <edit name="family" mode="prepend_first" binding="same">
            <string>Nimbus Roman Regular</string>
        </edit>
    </match>
    <match target="pattern">
        <test qual="any" name="family">
            <string>monospace</string>
        </test>
        <edit name="family" mode="prepend_first" binding="same">
            <string>SF Mono Powerline</string>
        </edit>
    </match>
</fontconfig>

Hey @njmyers thanks for this, very helpful!

Just I don't understand Prefer emoji font for all system aliases section is necessary 🤔

The rule of "SF Pro Text size >19 to SF Pro Display" doesn't work at all.