import javax.swing.tree.*;

static <A, B extends Cl<A>> JTree jDynamicTree(A root, IF1<A, B> makeChildren, O... _) {

  ret jDynamicTree(root, toF1(makeChildren), _);

}

static <A, B extends Cl<A>> JTree jDynamicTree(final A root, final F1<A, B> makeChildren, fO... _) {

  // optional wrapping/unwrapping of nodes for nicer printing

  optPar IF1 wrapNode;

  optPar IF1 unwrapNode;

  ret swing(func -> JTree {

    DefaultMutableTreeNode rootNode = new(callFOrKeep(wrapNode, root));

    rootNode.add(new DefaultMutableTreeNode(jDynamicTree_dummy()));

    final JTree tree = new JTree(rootNode);

    tree.setShowsRootHandles(true);

    tree.collapseRow(0);

    final bool keepChildrenOnCollapse = optParam(_, 'keepChildrenOnCollapse, false);

    bool makeChildrenIsFast = boolParam makeChildrenIsFast(_) || makeChildren == null;

    bool debug = boolPar debug(_);

    class jDynamicTree_Listener implements TreeWillExpandListener {

      public void treeWillCollapse(TreeExpansionEvent e) {}

      public void treeWillExpand(TreeExpansionEvent e) { pcall {

        if (debug) print("treeWillExpand");

        DefaultMutableTreeNode node = cast e.getPath().getLastPathComponent();

        if (!keepChildrenOnCollapse || jDynamicTree_isInDummyState(node)) {

          L<A> l = asList(callF(makeChildren, callFOrKeep(unwrapNode, (A) node.getUserObject())));

          if (makeChildrenIsFast

            ? replaceTreeNodeChildren_withDummyChild2(node, l, jDynamicTree_dummy(), makeChildren)

            : replaceTreeNodeChildren_withDummyChild(node, l, jDynamicTree_dummy()))

            ((DefaultTreeModel) tree.getModel()).nodeStructureChanged(node);

        }

      }}

    }

    tree.addTreeWillExpandListener(new jDynamicTree_Listener);

    ret tree;

  });

}