10.2.1 X11 Core Fonts

Today, the X11 core font system supports not only bitmap fonts but also scalable fonts, like Type1 fonts, TrueType, and OpenType fonts. Scalable fonts are only supported without antialiasing and subpixel rendering and the loading of large scalable fonts with glyphs for many languages may take a long time. Unicode fonts are also supported, but their use may be slow and require more memory.

The X11 core font system has a few inherent weaknesses. It is outdated and can no longer be extended in a meaningful way. Although it must be retained for reasons of backward compatibility, the more modern Xft and fontconfig system should be used if at all possible.

For its operation, the X server needs to know which fonts are available and where in the system it can find them. This is handled by a FontPath variable, which contains the path to all valid system font directories. In each of these directories, a file named fonts.dir lists the available fonts in this directory. The FontPath is generated by the X server at start-up. It searches for a valid fonts.dir file in each of the FontPath entries in the configuration file /etc/X11/xorg.conf. These entries are found in the Files section. Display the actual FontPath with xset q. This path may also be changed at runtime with xset. To add an additional path, use xset +fp <path>. To remove an unwanted path, use xset -fp <path>.

If the X server is already active, newly installed fonts in mounted directories can be made available with the command xset fp rehash. This command is executed by SuSEconfig --module fonts. Because the command xset needs access to the running X server, this only works if SuSEconfig --module fonts is started from a shell that has access to the running X server. The easiest way to achieve this is to assume root permissions by entering su and the root password. su transfers the access permissions of the user who started the X server to the root shell. To check if the fonts were installed correctly and are available by way of the X11 core font system, use the command xlsfonts to list all available fonts.

By default, openSUSE uses UTF-8 locales. Therefore, Unicode fonts should be preferred (font names ending with iso10646-1 in xlsfonts output). All available Unicode fonts can be listed with xlsfonts | grep iso10646-1. Nearly all Unicode fonts available in openSUSE contain at least the glyphs needed for European languages (formerly encoded as iso-8859-*).

10.2.2 Xft

From the outset, the programmers of Xft made sure that scalable fonts including antialiasing are supported well. If Xft is used, the fonts are rendered by the application using the fonts, not by the X server as in the X11 core font system. In this way, the respective application has access to the actual font files and full control of how the glyphs are rendered. This constitutes the basis for the correct display of text in a number of languages. Direct access to the font files is very useful for embedding fonts for printing to make sure that the printout looks the same as the screen output.

In openSUSE, the two desktop environments KDE and GNOME, Mozilla, and many other applications already use Xft by default. Xft is already used by more applications than the old X11 core font system.

Xft uses the fontconfig library for finding fonts and influencing how they are rendered. The properties of fontconfig are controlled by the global configuration file /etc/fonts/fonts.conf. Special configurations should be added to /etc/fonts/local.conf and the user-specific configuration file ~/.fonts.conf. Each of these fontconfig configuration files must begin with

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>

and end with

</fontconfig>

To add directories to search for fonts, append lines such as the following:

<dir>/usr/local/share/fonts/</dir>

However, this is usually not necessary. By default, the user-specific directory ~/.fonts is already entered in /etc/fonts/fonts.conf. Accordingly, all you need to do to install additional fonts is to copy them to ~/.fonts.

You can also insert rules that influence the appearance of the fonts. For example, enter

<match target="font">
 <edit name="antialias" mode="assign">
  <bool>false</bool>
 </edit>
</match>

to disable antialiasing for all fonts or

<match target="font">
 <test name="family">
  <string>Luxi Mono</string>
  <string>Luxi Sans</string>
 </test>
 <edit name="antialias" mode="assign">
 <bool>false</bool>
 </edit>
</match>

to disable antialiasing for specific fonts.

By default, most applications use the font names sans-serif (or the equivalent sans), serif, or monospace. These are not real fonts but only aliases that are resolved to a suitable font, depending on the language setting.

Users can easily add rules to ~/.fonts.conf to resolve these aliases to their favorite fonts:

<alias>
 <family>sans-serif</family>
 <prefer>
  <family>FreeSans</family>
 </prefer>
</alias>
<alias>
 <family>serif</family>
 <prefer>
  <family>FreeSerif</family>
 </prefer>
</alias>
<alias>
 <family>monospace</family>
 <prefer>
  <family>FreeMono</family>
 </prefer>
</alias>

Because nearly all applications use these aliases by default, this affects almost the entire system. Thus, you can easily use your favorite fonts almost everywhere without having to modify the font settings in the individual applications.

Use the command fc-list to find out which fonts are installed and available for use. For instance, the command fc-list returns a list of all fonts. To find out which of the available scalable fonts (:scalable=true) contain all glyphs required for Hebrew (:lang=he), their font names (family), their style (style), their weight (weight), and the name of the files containing the fonts, enter the following command:

fc-list ":lang=he:scalable=true" family style weight

The output of this command could look like the following:

Lucida Sans:style=Demibold:weight=200
DejaVu Sans:style=Bold Oblique:weight=200
Lucida Sans Typewriter:style=Bold:weight=200
FreeSerif:style=Bold,polkrepko:weight=200
FreeSerif:style=Italic,ležeče:weight=80
FreeSans:style=Medium,navadno:weight=80
DejaVu Sans:style=Oblique:weight=80
FreeSans:style=Oblique,ležeče:weight=80 

Important parameters that can be queried with fc-list: