the calling application. This also enforces the &lsquo;read-only&rsquo; nature of these values, i.e., this function cannot be used to manipulate the face.</p>
<p><code>value</code> is a void pointer because the values returned can be of various types.</p>
<p>If either <code>value</code> is <code>NULL</code> or <code>value_len</code> is too small, just the required memory size for the requested entry is returned.</p>
<p>The <code>idx</code> parameter is used, not only to retrieve elements of, for example, th