Копировать узлы с поддеревом TTreeView во второй TTreeView

{type
{: Callback to use to copy the data of a treenode when the 
   node itself is copied by CopySubtree. 
   @param oldnode is the old node 
   @param newnode is the new node 
   @Desc Use a callback of this type to implement your own algorithm 
         for a node copy. The default just uses the Assign method, which 
         produces a shallow copy of the nodes Data property. }
   TCopyDataProc = procedure(oldnode, newnode : TTreenode);

{: The default operation is to do a shallow copy of the node, via 
   Assign. }
procedure DefaultCopyDataProc(oldnode, newnode : TTreenode);
begin
  newnode.Assign(oldnode);
end;

{-- CopySubtree 
-------------------------------------------------------}
{: Copies the source node with all child nodes to the target treeview. 
@Param sourcenode is the node to copy 
@Param target is the treeview to insert the copied nodes into 
@Param targetnode is the node to insert the copy under, can be nil to 
  make the copy a top-level node. 
@Param CopyProc is the (optional) callback to use to copy a node. 
  If Nil is passed for this parameter theDefaultCopyDataProc will be 
  used. 
@Precondition  sourcenode <> nil, target <> nil, targetnode is either 
  nil or a node of target 
@Raises Exception if targetnode happens to be in the subtree rooted in 
  sourcenode. Handling that special case is rather complicated, so we 
  simply refuse to do it at the moment. 
}
{ Created 2003-04-09 by P. Below
-----------------------------------------------------------------------}
procedure CopySubtree(sourcenode : TTreenode; target : TTreeview;
  targetnode : TTreenode; CopyProc : TCopyDataProc = nil);
var
  anchor : TTreenode;
  child : TTreenode;
begin { CopySubtree }
  Assert(Assigned(sourcenode),
    'CopySubtree:sourcenode cannot be nil');
  Assert(Assigned(target),
    'CopySubtree: target treeview cannot be nil');
  Assert((targetnode = nil) or (targetnode.TreeView = target),
    'CopySubtree: targetnode has to be a node in the target treeview.');

  if (sourcenode.TreeView = target) and
    (targetnode.HasAsParent(sourcenode) or
    (sourcenode = targetnode)) then
    raise
      Exception.Create('CopySubtree cannot copy a subtree to one of the ' +
        'subtrees nodes.');

  if not Assigned(CopyProc) then
    CopyProc := DefaultCopyDataProc;

  anchor := target.Items.AddChild(targetnode, sourcenode.Text);
  CopyProc(sourcenode, anchor);
  child := sourcenode.GetFirstChild;
  while Assigned(child) do
  begin
    CopySubtree(child, target, anchor, CopyProc);
    child := child.getNextSibling;
  end; { While }
end; { CopySubtree }


procedure TForm1.Button1Click(Sender : TObject);
begin
  if assigned(treeview1.selected) then
    CopySubtree(treeview1.selected, treeview2, nil);
end;