Delphi - Drag and Drop usando o Treeview com Richedit

procedure TForm1.RichEdit1DragDrop(Sender, Source: TObject; X, Y: Integer);
var ponteiro : Tpoint;
    index: integer;
begin
  ponteiro:= Point( X, Y );
  Richedit1 := sender as TRichedit;
  index := Richedit1.perform(Messages.EM_CHARFROMPOS, 0,integer(@ponteiro));
  if index >= 0 Then
    begin
      Richedit1.selstart := index;
      RichEdit1.SelText := TreeView1.Selected.Text;
    end;
end;

procedure TForm1.TreeView1DragOver(Sender, Source: TObject; X, Y: Integer;
  State: TDragState; var Accept: Boolean);
begin
 Accept := (Source is TTreeView);
end;