Enum Curve 

pub enum Curve {
    Linear,
    EaseIn,
    EaseOut,
    EaseInOut,
    Emphasized,
    Cubic(f64, f64, f64, f64),
}

The animation vocabulary: the shell-fed frame clock (FrameTime) plus the pure easing/interpolation/spring math a widget or app advances it through, flat-re-exported from frust-core::anim. Time enters from the shell during paint (PaintCtx::frame_time); nothing here reads a clock. An easing curve mapping a normalized time t ∈ [0, 1] to an eased progress ∈ [0, 1].

The named variants are the standard CSS timing functions plus Material 3’s Emphasized easing; Curve::Cubic is a general cubic-Bézier for anything else. Evaluation clamps t to [0, 1] first.

Variants

Linear

t unchanged.

EaseIn

CSS ease-in — cubic-bezier(0.42, 0, 1, 1).

EaseOut

CSS ease-out — cubic-bezier(0, 0, 0.58, 1).

EaseInOut

CSS ease-in-out — cubic-bezier(0.42, 0, 0.58, 1).

Emphasized

Material 3 emphasized easing — cubic-bezier(0.2, 0.0, 0.0, 1.0).

Cubic(f64, f64, f64, f64)

A general cubic-Bézier timing function with control points (x1, y1) and (x2, y2) (endpoints fixed at (0, 0)/(1, 1)), the same parameterization CSS cubic-bezier() uses.

Implementations

impl Curve

pub fn transform(self, t: f64) -> f64

Evaluate the eased progress at normalized time t (clamped to [0, 1]).

pub fn interval(self, start: f64, end: f64) -> SegmentedCurve

Confine this curve to the [start, end] fraction of the timeline (Flutter’s Interval, TweenSequence-style curve segmentation): before start the result is 0.0, at/after end it’s 1.0, and in between it re-evaluates self at the rescaled local time (t - start) / (end - start).

This is what lets two widgets fade through each other on one shared controller — e.g. an outgoing element on curve.interval(0.0, 0.3) and an incoming one on curve.interval(0.3, 1.0).

start/end aren’t required to be [0, 1]-clamped or ordered here; a degenerate or inverted interval (end <= start) is defined as an instantaneous step at start: strictly before it the result is 0.0, at or after it’s 1.0 (see SegmentedCurve::transform).

Returns a SegmentedCurve rather than Curve itself: Curve is Copy (relied on by AnimationController, which derives Copy over its own curve: Curve field), and an Interval variant holding another Curve by value would make the enum infinitely-sized without indirection (Box), which would forfeit that Copy bound — so the segment lives in its own small Copy struct instead.

Trait Implementations

impl Clone for Curve

fn clone(&self) -> Curve

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Curve

impl Debug for Curve

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

Formats the value using the given formatter.

impl PartialEq for Curve

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Curve