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   5 <title>Shaping concepts: HarfBuzz Manual</title>
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  23 <div class="titlepage"><div><div><h2 class="title">
  24 <a name="shaping-concepts"></a>Shaping concepts</h2></div></div></div>
  25 <div class="toc"><dl class="toc">
  26 <dt><span class="section"><a href="shaping-concepts.html#text-shaping-concepts">Text shaping</a></span></dt>
  27 <dt><span class="section"><a href="complex-scripts.html">Complex scripts</a></span></dt>
  28 <dt><span class="section"><a href="shaping-operations.html">Shaping operations</a></span></dt>
  29 <dt><span class="section"><a href="unicode-character-categories.html">Unicode character categories</a></span></dt>
  30 <dt><span class="section"><a href="text-runs.html">Text runs</a></span></dt>
  31 <dt><span class="section"><a href="opentype-shaping-models.html">OpenType shaping models</a></span></dt>
  32 <dt><span class="section"><a href="graphite-shaping.html">Graphite shaping</a></span></dt>
  33 <dt><span class="section"><a href="aat-shaping.html">AAT shaping</a></span></dt>
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  36 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  37 <a name="text-shaping-concepts"></a>Text shaping</h2></div></div></div>
  38 <p>
  39       Text shaping is the process of transforming a sequence of Unicode
  40       codepoints that represent individual characters (letters,
  41       diacritics, tone marks, numbers, symbols, etc.) into the
  42       orthographically and linguistically correct two-dimensional layout
  43       of glyph shapes taken from a specified font.
  44     </p>
  45 <p>
  46       For some writing systems (or <span class="emphasis"><em>scripts</em></span>) and
  47       languages, the process is simple, requiring the shaper to do
  48       little more than advance the horizontal position forward by the
  49       correct amount for each successive glyph.
  50     </p>
  51 <p>
  52       But, for <span class="emphasis"><em>complex scripts</em></span>, any combination of
  53       several shaping operations may be required, and the rules for how
  54       and when they are applied vary from script to script. HarfBuzz and
  55       other shaping engines implement these rules.
  56     </p>
  57 <p>
  58       The exact rules and necessary operations for a particular script
  59       constitute a shaping <span class="emphasis"><em>model</em></span>. OpenType
  60       specifies a set of shaping models that covers all of
  61       Unicode. Other shaping models are available, however, including
  62       Graphite and Apple Advanced Typography (AAT).
  63     </p>
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