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  24 <a name="object-model-object-types"></a>Objects in HarfBuzz</h2></div></div></div>
  25 <p>
  26       <span class="emphasis"><em>Object types:</em></span> Opaque struct types are used
  27       for what HarfBuzz loosely calls "objects."  This doesn’t have
  28       much to do with the terminology from object-oriented programming
  29       (OOP), although some of the concepts are similar.
  30     </p>
  31 <p>
  32       In HarfBuzz, all object types provide certain
  33       lifecycle-management APIs.  Objects are reference-counted, and
  34       constructed with various <code class="function">create()</code> methods, referenced via
  35       <code class="function">reference()</code> and dereferenced using
  36       <code class="function">destroy()</code>.
  37     </p>
  38 <p>
  39       For example,
  40       the <code class="literal">hb_buffer_t</code> object has
  41       <code class="function">hb_buffer_create()</code> as its constructor,
  42       <code class="function">hb_buffer_reference()</code> to reference, and
  43       <code class="function">hb_buffer_destroy()</code> to dereference.
  44     </p>
  45 <p>
  46       After construction, each object's properties are accessible only
  47       through the setter and getter functions described in the API
  48       Reference manual.
  49     </p>
  50 <p>
  51       Key object types provided by HarfBuzz include:
  52     </p>
  53 <div class="itemizedlist"><ul class="itemizedlist compact" style="list-style-type: disc; ">
  54 <li class="listitem"><p>
  55           <span class="emphasis"><em>blobs</em></span>, which act as low-level wrappers around binary
  56           data. Blobs are typically used to hold the contents of a
  57           binary font file.
  58         </p></li>
  59 <li class="listitem"><p>
  60           <span class="emphasis"><em>faces</em></span>, which represent typefaces from a
  61           font file, but without specific parameters (such as size) set.
  62         </p></li>
  63 <li class="listitem"><p>
  64           <span class="emphasis"><em>fonts</em></span>, which represent instances of a
  65           face with all of their parameters specified.
  66         </p></li>
  67 <li class="listitem"><p>
  68           <span class="emphasis"><em>buffers</em></span>, which hold Unicode code points
  69           for characters (before shaping) and the shaped glyph output
  70           (after shaping).
  71         </p></li>
  72 <li class="listitem"><p>
  73           <span class="emphasis"><em>shape plans</em></span>, which store the settings
  74           that HarfBuzz will use when shaping a particular text
  75           segment. Shape plans are not generally used by client
  76           programs directly, but as we will see in a later chapter,
  77           they are still valuable to understand.
  78         </p></li>
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