 href="../../dart-ui/EngineLayer-class.html">EngineLayer</a></span> <span class="parameter-name">retainedLayer</span></span></li>
</ol>)
      
    </section>
    <section class="desc markdown">
      <p>Add a retained engine layer subtree from previous frames.</p>
<p>All the engine layers that are in the subtree of the retained layer will
be automatically appended to the current engine layer tree.</p>
<p>Therefore, when implementing a subclass of the <code>Layer</code> concept defined in
the rendering laye