code: protected void handlePaintCustom(final WTree tree, final XmlStringBuilder xml) {
  		TreeItemModel model = tree.getTreeModel();
  		TreeItemIdNode root = tree.getCustomTree();
  
  		Set<String> selectedRows = new HashSet(tree.getSelectedRows());
  		Set<String> expandedRows = new HashSet(tree.getExpandedRows());
  		WTree.ExpandMode mode = tree.getExpandMode();
  
  		// Process root nodes
  		for (TreeItemIdNode node : root.getChildren()) {
  			paintCustomItem(tree, mode, model, node, xml, selectedRows, expandedRows);
  		}
  	}
docs: Paint the custom tree layout.
  
  @param tree the WTree to render
  @param xml the XML string builder