You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: char_callback.rs
    path of file: ./repos/rust_minifb/examples
    
    the code of the file until where you have to start completion: use minifb::{InputCallback, Key, Window, WindowOptions};
use std::{cell::RefCell, rc::Rc};

const WIDTH: usize = 1280;
const HEIGHT: usize = 720;

type KeyVec = Rc<RefCell<Vec<u32>>>;

struct Input {
    keys: KeyVec,
}

impl InputCallback for Input {
    /// Will
    
fn main() {
    let mut buffer = vec![0u32; WIDTH * HEIGHT];

    let mut window = Window::new(
        "char_callback example - press ESC to exit",
        WIDTH,
        HEIGHT,
        WindowOptions::default(),
    )
    .expect("Unable to create the window");

    window.set_target_fps(60);

    let keys = KeyVec::new(RefCell::new(Vec::new()));
    window.set_input_callback(Box::new(Input { keys: keys.clone() }));

    // produces a wave pattern where the screen goes from red to blue, and vice-versa
    let mut wave: u8 = 0;
    let mut wave_direction: i8 = 1;
    while window.is_open() && !window.is_key_down(Key::Escape) {
        let red: u32 = (wave as u32) << 16;
        let green: u32 = 64 << 8;
        let blue: u32 = (255 - wave) as u32;
        let bg_color = red | green | blue;

        for pixel in buffer.iter_mut() {
            *pixel = bg_color;
        }

        // We unwrap here as we want this code to exit if it fails. Real applications may want to handle this in a different way
        window.update_with_buffer(&buffer, WIDTH, HEIGHT).unwrap();

        let mut keys = keys.borrow_mut();

        for t in keys.iter() {
            println!("Code point: {}, Character: {:?}", *t, char::from_u32(*t));
        }

        keys.clear();

        // switch color wave directions
        match wave.checked_add_signed(wave_direction) {
            Some(new_wave) => wave = new_wave,
            None => {
                wave_direction = -wave_direction;
                if wave_direction > 0 {
                    wave += 1;
                } else {
                    wave -= 1;
                }
            }
        }
    }
}