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| <div class="chapter"> |
| <div class="titlepage"><div><div><h2 class="title"> |
| <a name="shaping-concepts"></a>Shaping concepts</h2></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="shaping-concepts.html#text-shaping-concepts">Text shaping</a></span></dt> |
| <dt><span class="section"><a href="complex-scripts.html">Complex scripts</a></span></dt> |
| <dt><span class="section"><a href="shaping-operations.html">Shaping operations</a></span></dt> |
| <dt><span class="section"><a href="unicode-character-categories.html">Unicode character categories</a></span></dt> |
| <dt><span class="section"><a href="text-runs.html">Text runs</a></span></dt> |
| <dt><span class="section"><a href="opentype-shaping-models.html">OpenType shaping models</a></span></dt> |
| <dt><span class="section"><a href="graphite-shaping.html">Graphite shaping</a></span></dt> |
| <dt><span class="section"><a href="aat-shaping.html">AAT shaping</a></span></dt> |
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| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="text-shaping-concepts"></a>Text shaping</h2></div></div></div> |
| <p> |
| Text shaping is the process of transforming a sequence of Unicode |
| codepoints that represent individual characters (letters, |
| diacritics, tone marks, numbers, symbols, etc.) into the |
| orthographically and linguistically correct two-dimensional layout |
| of glyph shapes taken from a specified font. |
| </p> |
| <p> |
| For some writing systems (or <span class="emphasis"><em>scripts</em></span>) and |
| languages, the process is simple, requiring the shaper to do |
| little more than advance the horizontal position forward by the |
| correct amount for each successive glyph. |
| </p> |
| <p> |
| But, for <span class="emphasis"><em>complex scripts</em></span>, any combination of |
| several shaping operations may be required, and the rules for how |
| and when they are applied vary from script to script. HarfBuzz and |
| other shaping engines implement these rules. |
| </p> |
| <p> |
| The exact rules and necessary operations for a particular script |
| constitute a shaping <span class="emphasis"><em>model</em></span>. OpenType |
| specifies a set of shaping models that covers all of |
| Unicode. Other shaping models are available, however, including |
| Graphite and Apple Advanced Typography (AAT). |
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