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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>What is HarfBuzz?: HarfBuzz Manual</title> <meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> <link rel="home" href="index.html" title="HarfBuzz Manual"> <link rel="up" href="pt01.html" title="Part I. User's manual"> <link rel="prev" href="pt01.html" title="Part I. User's manual"> <link rel="next" href="why-do-i-need-a-shaping-engine.html" title="Why do I need a shaping engine?"> <meta name="generator" content="GTK-Doc V1.32 (XML mode)"> <link rel="stylesheet" href="style.css" type="text/css"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="5"><tr valign="middle"> <td width="100%" align="left" class="shortcuts"></td> <td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td> <td><a accesskey="u" href="pt01.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td> <td><a accesskey="p" href="pt01.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td> <td><a accesskey="n" href="why-do-i-need-a-shaping-engine.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td> </tr></table> <div class="chapter"> <div class="titlepage"><div><div><h2 class="title"> <a name="what-is-harfbuzz"></a>What is HarfBuzz?</h2></div></div></div> <div class="toc"><dl class="toc"> <dt><span class="section"><a href="what-is-harfbuzz.html#what-is-text-shaping">What is text shaping?</a></span></dt> <dt><span class="section"><a href="why-do-i-need-a-shaping-engine.html">Why do I need a shaping engine?</a></span></dt> <dt><span class="section"><a href="ch01s03.html">What does HarfBuzz do?</a></span></dt> <dt><span class="section"><a href="what-harfbuzz-doesnt-do.html">What HarfBuzz doesn't do</a></span></dt> <dt><span class="section"><a href="why-is-it-called-harfbuzz.html">Why is it called HarfBuzz?</a></span></dt> </dl></div> <p> HarfBuzz is a <span class="emphasis"><em>text-shaping engine</em></span>. If you give HarfBuzz a font and a string containing a sequence of Unicode codepoints, HarfBuzz selects and positions the corresponding glyphs from the font, applying all of the necessary layout rules and font features. HarfBuzz then returns the string to you in the form that is correctly arranged for the language and writing system. </p> <p> HarfBuzz can properly shape all of the world's major writing systems. It runs on all major operating systems and software platforms and it supports the major font formats in use today. </p> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="what-is-text-shaping"></a>What is text shaping?</h2></div></div></div> <p> Text shaping is the process of translating a string of character codes (such as Unicode codepoints) into a properly arranged sequence of glyphs that can be rendered onto a screen or into final output form for inclusion in a document. </p> <p> The shaping process is dependent on the input string, the active font, the script (or writing system) that the string is in, and the language that the string is in. </p> <p> Modern software systems generally only deal with strings in the Unicode encoding scheme (although legacy systems and documents may involve other encodings). </p> <p> There are several font formats that a program might encounter, each of which has a set of standard text-shaping rules. </p> <p>The dominant format is <a class="ulink" href="http://www.microsoft.com/typography/otspec/" target="_top">OpenType</a>. The OpenType specification defines a series of <a class="ulink" href="https://github.com/n8willis/opentype-shaping-documents" target="_top">shaping models</a> for various scripts from around the world. These shaping models depend on the font incorporating certain features as <span class="emphasis"><em>lookups</em></span> in its <code class="literal">GSUB</code> and <code class="literal">GPOS</code> tables. </p> <p> Alternatively, OpenType fonts can include shaping features for the <a class="ulink" href="https://graphite.sil.org/" target="_top">Graphite</a> shaping model. </p> <p> TrueType fonts can also include OpenType shaping features. Alternatively, TrueType fonts can also include <a class="ulink" href="https://developer.apple.com/fonts/TrueType-Reference-Manual/RM09/AppendixF.html" target="_top">Apple Advanced Typography</a> (AAT) tables to implement shaping support. AAT fonts are generally only found on macOS and iOS systems. </p> <p> Text strings will usually be tagged with a script and language tag that provide the context needed to perform text shaping correctly. The necessary <a class="ulink" href="https://docs.microsoft.com/en-us/typography/opentype/spec/scripttags" target="_top">script</a> and <a class="ulink" href="https://docs.microsoft.com/en-us/typography/opentype/spec/languagetags" target="_top">language</a> tags are defined by OpenType. </p> </div> </div> <div class="footer"> <hr>Generated by GTK-Doc V1.32</div> </body> </html>