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procedure TForm1.Button1Click(Sender: TObject);
const
 C_WishedLine_ZeroBased=11;
var
  pt: TPoint;
  CharPos:Integer;
begin
  CharPos :=richedit1.Perform(messages.EM_LINEINDEX, C_WishedLine_ZeroBased,0);
  richedit1.Perform(messages.EM_POSFROMCHAR, WPARAM(@pt), CharPos);
  Label1.top := richedit1.Top + pt.Y;
//  Mouse.CursorPos := richedit1.ClientToScreen(pt);

end;