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Asked: 2021-05-03 06:55:36 +0800 CST

Font configuration rule priority

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If I have two files in /etc/fonts/conf.d/.

One being:

<fontconfig>
<alias>
 <family>sans-serif</family>
 <prefer>
   <family>Noto Color Emoji</family>
 </prefer>
</alias>
</fontconfig>

And the other one being:

<fontconfig>
<alias>
 <family>sans-serif</family>
 <prefer>
   <family>Noto Emoji</family>
 </prefer>
</alias>
</fontconfig>

What would the outcome be after they are both read in?

Reason behind the question --
I have a huge and messy font-selection file. If I can somehow build the font selection from files step by step, that'll be hugely tidy up my messy font-selection file. So,

Using the Noto Emoji as an example, how can I build my font selection step by step so that Noto Color Emoji is the default and Noto Emoji is the fallback?

fonts

2 Answers

  1. It depends on the number prepending the file name. For instance:

    10-my-color.conf
20-my-other.conf

    That should give the Color variant higher precedence.

    P.S. Have you considered to use the ~/.config/fontconfig/conf.d directory for the purpose? That way you wouldn't mix your own files with the files installed by various packages.

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  2. alias element of fontconfig support a fallback/priority list with default selection. No need for multiple files or alias rules. One alias rules should be enough for single family match.

    From fontconfig manpage:

    <alias>

    Alias elements provide a shorthand notation for the set of common
match operations needed to substitute one font family for another.

They contain a <family> element followed by optional <prefer>,
<accept> and <default> elements. Fonts matching the <family>
element are edited to prepend the list of <prefer>ed families
before the matching <family>, append the <accept>able families
after the matching <family> and append the <default> families to
the end of the family list.

    <family>

    Holds a single font family name

    <prefer>, <accept>, <default>

    These hold a list of <family> elements to be used by the <alias>
element.

    Here your example with extended setup:

    <fontconfig>
 <alias>
  <family>sans-serif</family>
  <!-- <accept> list if needed -->
  <prefer>
   <family>Noto Color Emoji</family>
   <family>Noto Emoji</family>
   <!-- you may add more font families here -->
  </prefer>
  <!-- <default> list if needed -->
 </alias>
</fontconfig>

    If you want to force the font bypass matching use accept instead.

    By the way, you may take/think priority of <prefer> as medium/prefered, <accept> as strong/override, <default> as weak/fallback.

    Here are a good examples: Beyond Linux® From Scratch (System V Edition) - Overview of Fontconfig

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