fontconfig

Fontconfig is a library for configuring and customizing font access.

Fontconfig can:

1. discover new fonts when installed automatically, removing a common source of configuration problems.
2. perform font name substitution, so that appropriate alternative fonts can be selected if fonts are missing.
3. identify the set of fonts required to completely cover a set of languages.
4. have GUI configuration tools built as it uses an XML-based configuration file (though with autodiscovery, we believe this need is minimized).
5. efficiently and quickly find the fonts you need among the set of fonts you have installed, even if you have installed thousands of fonts, while minimzing memory usage.
6. be used in concert with the X Render Extension and FreeType to implement high quality, anti-aliased and subpixel rendered text on a display.

Fontconfig does not:

1. render the fonts themselves (this is left to FreeType or other rendering mechanisms)
2. depend on the X Window System in any fashion, so that printer only applications do not have such dependencies

Fontconfig is a library designed to provide system-wide font configuration, customization and application access.

Fontconfig contains two essential modules, the configuration module which builds an internal configuration from XML files and the matching module which accepts font patterns and returns the nearest matching font. Font Configuration

The configuration module consists of the FcConfig datatype, libexpat and FcConfigParse which walks over an XML tree and amends a configuration with data found within. From an external perspective, configuration of the library consists of generating a valid XML tree and feeding that to FcConfigParse. The only other mechanism provided to applications for changing the running configuration is to add fonts and directories to the list of application-provided font files.

The intent is to make font configurations relatively static, and shared by as many applications as possible. It is hoped that this will lead to more stable font selection when passing names from one application to another. XML was chosen as a configuration file format because it provides a format which is easy for external agents to edit while retaining the correct structure and syntax.

Font configuration is separate from font matching; applications needing to do their own matching can access the available fonts from the library and perform private matching. The intent is to permit applications to pick and choose appropriate functionality from the library instead of forcing them to choose between this library and a private configuration mechanism. The hope is that this will ensure that configuration of fonts for all applications can be centralized in one place. Centralizing font configuration will simplify and regularize font installation and customization.