This document provides details on the design and implementation of the
FreeType 2 library. Its goal is to allow developers to better
understand the way how FreeType 2 is organized, in order to let them
extend, customize, and debug it.
Before anything else, it is important to understand the
purpose of this library, i.e., why it has been written:
It allows client applications to access font files easily,
wherever they could be stored, and as independently of the font format
Easy retrieval of global font data most commonly found in
normal font formats (i.e. global metrics, encoding/charmaps,
It allows easy retrieval of individual glyph data
(metrics, images, name, anything else).
Access to font format-specific "features" whenever
possible (e.g. SFNT tables, Multiple Masters, OpenType Layout tables,
Its design has also severely been influenced by the following
High portability. The library must be able to run on any
kind of environment. This requirement introduces a few drastic
choices that are part of FreeType 2's low-level system
Extendability. New features should be added with the
least modifications in the library's code base. This requirement
induces an extremely simple design where nearly all operations are
provided by modules.
Customization. It should be easy to build a version of the
library that only contains the features needed by a specific project.
This really is important when you need to integrate it in a font
server for embedded graphics libraries.
Compactness and efficiency. The primary target
for this library are embedded systems with low cpu and memory
The rest of this document is divided in several sections. First, a few
chapters will present the library's basic design as well as the
objects/data managed internally by FreeType 2.
A later section is then dedicated to library customization, relating
such topics as system-specific interfaces, how to write your own module
and how to tailor library initialization & compilation to your needs.