code: def preferred_width(self, cli, max_available_width):
          
          if cli.current_buffer.complete_state:
              state = cli.current_buffer.complete_state
              return 2 + max(get_cwidth(c.display_meta) for c in state.current_completions)
          else:
              return 0
docs: Report the width of the longest meta text as the preferred width of this control.
  
          It could be that we use less width, but this way, we're sure that the
          layout doesn't change when we select another completion (E.g. that
          completions are suddenly shown in more or fewer columns.)