fruit UI for 3DS

the start of this god-foresaken UI library. this is the first time I’ve written code in a few months, and I don’t have much experience writing a library, so bare with me!

I decided on an immediate mode UI design inspired by the likes of egui. however, it is wasteful to have to create resources every frame for. as such, I decided to implement memoization. I’m not sure if this is the best way, but:

for every pub trait UiObj: Any
there is a pub trait UiObjMemoize: dyn_hash::DynHash {}.

this latter memoize trait is constructed only from the immediate mode method, and does not hold any other state required for blitting the object.

for instance, a if container.button("hello, world!") { /* ... */ } will create an instance of the struct

#[derive(Hash)]
pub(crate) struct ButtonMemoizeState<'a>(&'a str, &'a ButtonStyle);

as ButtonMemoizeState("hello, world!", &ButtonStyle::default()).

this is then looked up in a hashmap of the Container of the field
pub children: HashMap<u64, Box<dyn UiObj>>.
note that I am using a u64 here rather than a dyn UiObjMemoize – this is to workaround a limitation where you cannot use a dyn trait object as a hashmap key. instead, I use a stable hasher from the fx_hasher crate where I hash it to a u64, acheiving the same result but slightly more long-winded. (fn hash_memoized_obj<T: UiObjMemoize>(v: &T) -> u64;)

technicality aside, the API now looks like:

fn render(ui: &mut fruit::Ui) {
    // todo: enter container with closure
    if ui.top_root.button("HAIII") {
        println!(">w<");
    };
}

no tangible example yet, just base code.

todo: garbage collection / reference counting for memoization, closures and ctru context (HID, GFX, APT, citro2d::Instance, app state), layouts, rendering backend.
blockers: rendering backend (notably C2D_Text).

https://git.sr.ht/~sheepy/fruit/tree/460c3a620a6ecfec7da690d71e185de887286c18