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;

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