Easing curves for tuples

[mweatherley]

Objective

Make it so that users can ease between tuples of easeable values.

Solution

Use variadics_please's all_tuples_enumerated macro to generate code that creates these trait implementations. For two elements, the result looks like this:

impl<T0: Ease, T1: Ease> Ease for (T0, T1) {
    fn interpolating_curve_unbounded(start: Self, end: Self) -> impl Curve<Self> {
        let curve_tuple = (
            <T0 as Ease>::interpolating_curve_unbounded(start.0, end.0),
            <T1 as Ease>::interpolating_curve_unbounded(start.1, end.1),
        );
        FunctionCurve::new(Interval::EVERYWHERE, move |t| {
            (
                curve_tuple.0.sample_unchecked(t),
                curve_tuple.1.sample_unchecked(t),
            )
        })
    }
}

Testing

It compiles, and I futzed about with some manual examples, which seem to work as expected.

---

Showcase

Easing curves now support easing tuples of values that can themselves be eased. For example:

// Easing between two `(Vec3, Quat)` values:
let easing_curve = EasingCurve::new(
    (vec3(0.0, 0.0, 0.0), Quat::from_rotation_z(-FRAC_PI_2)),
    (vec3(1.0, 1.0, 1.0), Quat::from_rotation_z(FRAC_PI_2)),
    EaseFunction::ExponentialInOut
);

[Jondolf]

Cool!