A Quicksilver Chanukah, Day 2: Platter

This year saw the release of async/.await in stable Rust, marking a huge change in how asynchronous code is written. Previously, one would have to chain a series of combinators onto a Future instance to accomplish asyncrhonous tasks. In Quicksilver, this was used for asset loading (for compatibility with the web backend), and has been a frequent source of pain.

Something as simple as loading a file, reading its contents, and loading a series of images based on those contents might look like this psuedo-Rust:

let images: load_file("my_manifest_path")
    .map(parse_file_contents)
    .and_then(|image_paths| join_all(
        image_paths
            .map(load_file)
            .map(|file| file.and_then(parse_image))
    );

render_loading();
loop {
    // Core application loop
    if images.is_ready {
        render_frame(&images);
    }
}

This is fairly hard to read, and requires a bit of domain-specific knowledge of the combinators to achieve it. Worse still is introducing more than one of these combinator chains, and trying to execute game logic only if they complete. This snippet is plenty complex, and hasn’t even touched error handling.

Introducing platter, a new async-enabled crate with a single, simple task: load files on desktop and web with an easy API.

render_loading();
let contents: load_file("my_manifest_path").await?;
let image_paths: parse_file_contents(contents);
let images: Vec::new();
for image_path in image_paths {
    let image_file: load_file(image_path).await?;
    images.push(parse_image(image_file)?);
}
loop {
    render_frame(&images);
}

We can still make use of the combinators in a more functional-programming style if we wish, but now it’s much clearer:

render_loading();
let contents: load_file("my_manifest_path").await;
let image_futures: parse_file_contents(contents)
    .map(load_file);
let images: Vec<Image>: try_join_all(image_futures)
    .await?
    .map(parse_image)
    .collect()?;
loop {
    render_frame(&images);
}

platter is small and can be plugged into your own game framework or game project if you want to harness async/await to load files on desktop and web. It will be a major part of the new Quicksilver application lifecyle!

That’s Day 2 down, but there are 6 more days of Quicksilver Chanukah: