* @param index the index of the child to add
*/
private void renderAddChildDirective(RenderContext rc, ServerComponentUpdate update, SplitPane splitPane, int index) {
String elementId = ContainerInstance.getElementId(splitPane);
ServerMessage serverMessage = rc.getServerMessage();
Element partElement = serverMessage.addPart(ServerMessage.GROUP_ID_UPDATE, "EchoSplitPane.MessageProcessor");
Element addChildElement = serverMessage.getDocument().createElement("add-child");
addChildElement.setAttribute("eid", elementId);
addChildElement.setAttribute("index", Integer.toString(index));
Component child = splitPane.getVisibleComponent(index);
renderLayoutData(rc, addChildElement, child, index);