Method new

std/src/console/readline.rs:339–402

Creates a new interactive line editor and renders its initial state.

(
        console: &'a mut dyn Console,
        prompt: &str,
        previous: &str,
        mut history: Option<&'h mut Vec<String>>,
        echo: bool,
    )

    /// Creates a new interactive line editor and renders its initial state.
    fn new(
        console: &'a mut dyn Console,
        prompt: &str,
        previous: &str,
        mut history: Option<&'h mut Vec<String>>,
        echo: bool,
    ) -> io::Result<Self> {
        let console_width = {
            let console_size = console.size_chars()?;
            usize::from(console_size.x)
        };

        let mut prompt = Cow::from(prompt);
        let mut prompt_len = prompt.len();
        if prompt_len >= console_width {
            // TODO(jmmv): This slices by bytes and can split non-ASCII prompts.
            if console_width >= 5 {
                prompt = Cow::from(format!("{}...", &prompt[0..console_width - 5]));
            } else {
                prompt = Cow::from("");
            }
            prompt_len = prompt.len();
        }

        let input_width = {
            // Assumes that the prompt was printed at column 0.  If that was not the case, line
            // length calculation does not work.
            let width = console_width - prompt_len;
            width.saturating_sub(1)
        };

        let line = LineBuffer::from(previous);
        let pos = line.len();
        let view_start = if input_width == 0 { 0 } else { pos.saturating_sub(input_width) };
        let history_pos = match history.as_mut() {
            Some(history) => {
                history.push(line.to_string());
                history.len() - 1
            }
            None => 0,
        };

        let mut readline = Self {
            console,
            history,
            echo,
            input_width,
            line,
            pos,
            view_start,
            rendered: String::new(),
            rendered_len: 0,
            history_pos,
        };
        readline.view_start = readline.adjust_view(readline.pos, readline.view_start);
        readline.sync_rendered();

        if !prompt.is_empty() || !readline.rendered.is_empty() {