Struct Tween 

pub struct Tween {
    pub from: f32,
    pub to: f32,
    pub duration: f32,
    pub curve: Curve,
}

Injected-clock tween of a scalar from from→to over duration seconds, eased by a Curve. The single “animate a value over a duration” primitive the form facets were missing (hover/selection/expand, drawer slide-ins).

Determinism (FC-7): a Tween holds no egui state and no wall-clock — you evaluate it at the elapsed seconds you own (the same dt/clock model as SmoothScroll and focus::motion_progress), so snapshots stay reproducible. It is a pure value, Copy, cheap to rebuild each frame.

use facett_core::effects::{Tween, Curve};
let t = Tween::new(0.0, 100.0, 0.2, Curve::EaseInOutCubic);
assert_eq!(t.value_at(0.0), 0.0);     // start
assert_eq!(t.value_at(0.2), 100.0);   // end
assert!(t.is_done(0.2));

Fields

from: f32

Value at elapsed <= 0.

to: f32

Value at elapsed >= duration.

duration: f32

Tween length in seconds. <= 0 snaps instantly to to (honours Motion::duration == 0, the reduced-motion / Device setting).

curve: Curve

Easing curve.

Implementations

impl Tween

pub fn new(from: f32, to: f32, duration: f32, curve: Curve) -> Self

A tween from→to over duration seconds with curve.

pub fn from_motion(motion: &Motion, from: f32, to: f32, curve: Curve) -> Self

A standard-duration tween from the theme’s Motion token.

pub fn from_motion_fast( motion: &Motion, from: f32, to: f32, curve: Curve, ) -> Self

A faster tween using Motion::fast — for small/cheap transitions.

pub fn value_at(&self, elapsed: f32) -> f32

Eased value at elapsed seconds since the tween started. value_at(<=0) == from, value_at(>=duration) == to; duration <= 0 ⇒ to.

pub fn progress_at(&self, elapsed: f32) -> f32

Eased progress ∈[0,1] (the to-fraction) at elapsed — the lerp factor to drive geometry/colour interpolation yourself.

pub fn is_done(&self, elapsed: f32) -> bool

Has the tween reached to by elapsed?

Trait Implementations

impl Clone for Tween

fn clone(&self) -> Tween

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Tween

impl Debug for Tween

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for Tween

fn eq(&self, other: &Tween) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Tween