procedure TTreeViewForm.TreeView1ContextPopup(Sender: TObject; MousePos: TPoint; var Handled: Boolean) ;
var
  treeNode : TTreenode;
  treeView : TTreeView;
begin
  treeView := TTreeview(sender) ;

  treeNode := treeView.GetNodeAt(MousePos.X, MousePos.Y) ;

  if Assigned(treeNode) then
  begin
    treeView.Selected := treeNode;
    // "mnuDoIt1" is the name of one of the popup menu items
    mnuDoIt1.Caption := Format('Do For Item: %s', [treeNode.Text]) ;
    //popup will display automatically
  end
  else
  begin
    //no node under mouse - do not display popup
    Handled := true;
  end;
end;