19 The X Window System #

SUSE Linux Enterprise Server comes with a sysconfig layer above Fontconfig. This is a good starting point for experimenting with font configuration. To change the default settings, edit the configuration file /etc/sysconfig/fonts-config. (or use the YaST sysconfig module). After you have edited the file, run fonts-config:

sudo /usr/sbin/fonts-config

Restart the application to make the effect visible. Keep in mind the following issues:

There are several sysconfig variables which can be altered. See man 1 fonts-config or the help page of the YaST sysconfig module. The following variables are examples:

The following list provides some configuration examples, sorted from the “most readable” fonts (more contrast) to “most beautiful” (more smoothed).

Fontconfig's configuration format is the eXtensible Markup Language (XML). These few examples are not a complete reference, but a brief overview. Details and other inspiration can be found in man 5 fonts-conf or in /etc/fonts/conf.d/.

The central Fontconfig configuration file is /etc/fonts/fonts.conf, which—along other work—includes the whole /etc/fonts/conf.d/ directory. To customize Fontconfig, there are two places where you can insert your changes:

User-specific changes overwrite any system-wide settings.

Note: Deprecated User Configuration File

The file ~/.fonts.conf is marked as deprecated and should not be used anymore. Use ~/.config/fontconfig/fonts.conf instead.

Every configuration file needs to have a fontconfig element. As such, the minimal file looks like this:

<?xml version="1.0"?>
   <!DOCTYPE fontconfig SYSTEM "fonts.dtd">
   <fontconfig>
   <!-- Insert your changes here -->
   </fontconfig>

If the default directories are not enough, insert the dir element with the respective directory:

<dir>/usr/share/fonts2</dir>

Fontconfig searches recursively for fonts.

Font-rendering algorithms can be chosen with following Fontconfig snippet (see Example 19.1, “Specifying Rendering Algorithms”):

<match target="font">
 <test name="family">
  <string>FAMILY_NAME</string>
 </test>
 <edit name="antialias" mode="assign">
  <bool>true</bool>
 </edit>
 <edit name="hinting" mode="assign">
  <bool>true</bool>
 </edit>
 <edit name="autohint" mode="assign">
  <bool>false</bool>
 </edit>
 <edit name="hintstyle" mode="assign">
  <const>hintfull</const>
 </edit>
</match>

Various properties of fonts can be tested. For example, the <test> element can test for the font family (as shown in the example), size interval, spacing, font format, and others. When abandoning <test> completely, all <edit> elements will be applied to every font (global change).

The rules from Example 19.2, “Aliases and Family Name Substitutions” create a prioritized family list (PFL). Depending on the element, different actions are performed:

Putting this together, when snippets occur in the order Rule 1 - Rule 2 - Rule 3 and the user requests “Alegreya SC”, then the PFL is created as depicted in Table 19.1, “Generating PFL from Fontconfig rules”.

In Fontconfig's metrics, the family name has the highest priority over other patterns, like style, size, etc. Fontconfig checks which family is currently installed on the system. If “Alegreya SC” is installed, then Fontconfig returns it. If not, it asks for “Droid Serif”, etc.

Be careful. When the order of Fontconfig snippets is changed, Fontconfig can return different results, as depicted in Table 19.2, “Results from Generating PFL from Fontconfig Rules with Changed Order”.

Note: Implication

Think of the <default> alias as a classification or inclusion of this group (if not installed). As the example shows, <default> should always precede the <prefer> and <accept> aliases of that group.

<default> classification is not limited to the generic aliases serif, sans-serif and monospace. See /usr/share/fontconfig/conf.avail/30-metric-aliases.conf for a complex example.

The following Fontconfig snippet in Example 19.3, “Aliases and Family Name Substitutions” creates a serif group. Every family in this group could substitute others when a former font is not installed.

<alias>
 <family>Alegreya SC</family>
 <default>
  <family>serif</family>
 </default>
</alias>
<alias>
 <family>Droid Serif</family>
 <default>
  <family>serif</family>
 </default>
</alias>
<alias>
 <family>STIXGeneral</family>
 <default>
  <family>serif</family>
 </default>
</alias>
<alias>
 <family>serif</family>
 <accept>
  <family>Droid Serif</family>
  <family>STIXGeneral</family>
  <family>Alegreya SC</family>
 </accept>
</alias>

Priority is given by the order in the <accept> alias. Similarly, stronger <prefer> aliases can be used.

Example 19.2, “Aliases and Family Name Substitutions” is expanded by Example 19.4, “Aliases and Family Names Substitutions”.

The expanded configuration from Example 19.4, “Aliases and Family Names Substitutions” would lead to the following PFL evolution:

Note: Implications.

• In case multiple <accept> declarations for the same generic name exist, the declaration that is parsed last “wins”. If possible, do not use <accept> after user (/etc/fonts/conf.d/*-user.conf) when creating a system-wide configuration.

• In case multiple <prefer declarations for the same generic name exist, the declaration that is parsed last “wins”. If possible, do not use <prefer> before user in the system-wide configuration.

• Every <prefer> declaration overwrites <accept> declarations for the same generic name. If the administrator wants to allow the user to utilize <accept> and not only <prefer>, the administrator should not use <prefer> in the system-wide configuration. On the other hand, as users mostly use <prefer>, this should not have any detrimental effect. We also see the use of <prefer> in system-wide configurations.