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| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="unicode-character-categories"></a>Unicode character categories</h2></div></div></div> |
| <p> |
| Shaping models are typically specified with respect to how |
| scripts are defined in the Unicode standard. |
| </p> |
| <p> |
| Every codepoint in the Unicode Character Database (UCD) is |
| assigned a <span class="emphasis"><em>Unicode General Category</em></span> (UGC), |
| which provides the most fundamental information about the |
| codepoint: whether the codepoint represents a |
| <span class="emphasis"><em>Letter</em></span>, a <span class="emphasis"><em>Mark</em></span>, a |
| <span class="emphasis"><em>Number</em></span>, <span class="emphasis"><em>Punctuation</em></span>, a |
| <span class="emphasis"><em>Symbol</em></span>, a <span class="emphasis"><em>Separator</em></span>, |
| or something else (<span class="emphasis"><em>Other</em></span>). |
| </p> |
| <p> |
| These UGC properties are "Major" categories. Each codepoint is |
| further assigned to a "minor" category within its Major |
| category, such as "Letter, uppercase" (<code class="literal">Lu</code>) or |
| "Letter, modifier" (<code class="literal">Lm</code>). |
| </p> |
| <p> |
| Shaping models are concerned primarily with Letter and Mark |
| codepoints. The minor categories of Mark codepoints are |
| particularly important for shaping. Marks can be nonspacing |
| (<code class="literal">Mn</code>), spacing combining |
| (<code class="literal">Mc</code>), or enclosing (<code class="literal">Me</code>). |
| </p> |
| <p> |
| In addition to the UGC property, codepoints in the Indic and |
| Southeast Asian scripts are also assigned |
| <span class="emphasis"><em>Unicode Indic Syllabic Category</em></span> (UISC) and |
| <span class="emphasis"><em>Unicode Indic Positional Category</em></span> (UIPC) |
| properties that provide more detailed information needed for |
| shaping. |
| </p> |
| <p> |
| The UISC property sub-categorizes Letters and Marks according to |
| common script-shaping behaviors. For example, UISC distinguishes |
| between consonant letters, vowel letters, and vowel marks. The |
| UIPC property sub-categorizes Mark codepoints by the relative visual |
| position that they occupy (above, below, right, left, or in |
| multiple positions). |
| </p> |
| <p> |
| Some complex scripts require that the text run be split into |
| syllables. What constitutes a valid syllable in these |
| scripts is specified in regular expressions, formed from the |
| Letter and Mark codepoints, that take the UISC and UIPC |
| properties into account. |
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