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The design of FreeType 2
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Copyright 1998-2000 David Turner (<a
href="mailto:david@freetype.org">david@freetype.org</a>)<br>
Copyright 2000 The FreeType Development Team (<a
href="mailto:devel@freetype.org">devel@freetype.org</a>)
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<h1>
Introduction
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<p>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.</p>
<p>Before anything else, it is important to understand the
<em>purpose</em> of this library, i.e., why it has been written:</p>
<ul>
<li>
<p>It allows client applications to <em>access font files easily</em>,
wherever they could be stored, and as independently of the font format
as possible.</p>
</li>
<li>
<p>Easy <em>retrieval of global font data</em> most commonly found in
normal font formats (i.e. global metrics, encoding/charmaps,
etc.).</p>
</li>
<li>
<p>It allows easy <em>retrieval of individual glyph data</em>
(metrics, images, name, anything else).</p>
</li>
<li>
<p><em>Access to font format-specific "features"</em> whenever
possible (e.g. SFNT tables, Multiple Masters, OpenType Layout tables,
etc.).</p>
</li>
</ul>
<p>Its design has also severely been influenced by the following
requirements:</p>
<ul>
<li>
<p><em>High portability</em>. 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
interface.</p>
</li>
<li>
<p><em>Extendability</em>. 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.</p>
</li>
<li>
<p><em>Customization</b>. 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.</p>
</li>
<li>
<p><em>Compactness</em> and <em>efficiency</em>. The primary target
for this library are embedded systems with low cpu and memory
resources.</p>
</li>
</ul>
<p>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.</p>
<p>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.</p>
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