Method do_up_down

std/src/console/readline.rs:292–323

Navigates through the command history.

(&mut self, delta: isize)

    /// Navigates through the command history.
    fn do_up_down(&mut self, delta: isize) -> io::Result<DispatchResult> {
        let (new_history_pos, new_line) = {
            let history = match self.history.as_deref_mut() {
                Some(history) => history,
                None => return Ok(DispatchResult::Continue),
            };

            let new_history_pos = if delta < 0 {
                if self.history_pos == 0 {
                    return Ok(DispatchResult::Continue);
                }
                self.history_pos - 1
            } else {
                if self.history_pos == history.len() - 1 {
                    return Ok(DispatchResult::Continue);
                }
                self.history_pos + 1
            };

            history[self.history_pos] = self.line.to_string();
            (new_history_pos, history[new_history_pos].clone())
        };

        let old_pos = self.current_pos();
        let clear_len = self.rendered_len;
        self.history_pos = new_history_pos;
        self.line = LineBuffer::from(&new_line);
        self.pos = self.line.len();
        self.reset_view_to_end();
        self.redraw_line(old_pos, clear_len, self.current_pos())?;
        Ok(DispatchResult::Continue)
    }

    /// Finalizes history bookkeeping and returns the edited line.
    fn finish(mut self) -> String {