href="glCopyTexSubImage2D.html"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>),
            which is taken from the frame buffer values of
            <em class="parameter"><code>read</code></em>.
        </p>
        <p>
            If the calling thread has already a current rendering context, that
            context is flushed and marked as no longer current.
        </p>
        <p>
            The first time that <em class="parameter"><code>context</code>