void setTopControl (int index) {
		if (index == -1 || children.length == 0) {
			currentLayer = -1;
			topControl.setText ("");
		} else {
			currentLayer = index;
			stackLayout.topControl = children [currentLayer];
			layoutComposite.layout ();
			TableItem item = table.getItem(currentLayer);
			topControl.setText (item.getText(0));
		}
		backButton.setEnabled(children.length > 1 && currentLayer > 0);
		advanceButton.setEnabled(children.length > 1 && currentLayer < children.length - 1);
	}