Enum Easing 

pub enum Easing {
    Linear,
    SineIn,
    SineOut,
    SineInOut,
    QuadraticIn,
    QuadraticOut,
    QuadraticInOut,
    CubicIn,
    CubicOut,
    CubicInOut,
    QuarticIn,
    QuarticOut,
    QuarticInOut,
    ExponentialIn,
    ExponentialOut,
    ExponentialInOut,
    BackIn {
        overshoot: f64,
    },
    BackOut {
        overshoot: f64,
    },
    BackInOut {
        overshoot: f64,
    },
    ElasticOut {
        amplitude: f64,
        period: f64,
    },
    BounceOut,
    Steps(u32),
    CubicBezier {
        x1: f64,
        y1: f64,
        x2: f64,
        y2: f64,
    },
    Custom(Arc<dyn Fn(f64) -> f64 + Send + Sync>),
}

A normalized double-precision easing curve, independent of clip duration.

Finite input is clamped to the unit interval with exact zero/one endpoints. Output may overshoot. Parameters are checked when sampled; invalid parameters, nonfinite progress and nonfinite custom output panic rather than being hidden.

use motion_core::prelude::*;
use motion_core::{
    DisplayList, RasterLimits, ResourcePool, ValidatedDisplayList, MAX_PATH_VERBS,
    MAX_STROKE_VERBS, MAX_SVG_PATH_BYTES, sample_offsets,
};
let movement = Tween::new(0.0_f64, 100.0, 2.seconds()).easing(Easing::CubicOut);
assert_eq!(movement.sample(1.seconds()), 87.5);

Variants

Linear

Constant speed.

SineIn

Sinusoidal acceleration.

SineOut

Sinusoidal deceleration.

SineInOut

Symmetric sinusoidal movement.

QuadraticIn

Quadratic acceleration.

QuadraticOut

Quadratic deceleration.

QuadraticInOut

Symmetric quadratic movement.

CubicIn

Cubic acceleration.

CubicOut

Cubic deceleration.

CubicInOut

Symmetric cubic movement.

QuarticIn

Quartic acceleration.

QuarticOut

Quartic deceleration.

QuarticInOut

Symmetric quartic movement.

ExponentialIn

Base-two exponential acceleration, pinned at zero.

ExponentialOut

Base-two exponential deceleration, pinned at one.

ExponentialInOut

Symmetric exponential movement.

BackIn

Initial backward movement before acceleration.

Fields

overshoot: f64

Finite, nonnegative backward coefficient.

BackOut

Overshoots the target before settling.

Fields

overshoot: f64

Finite, nonnegative overshoot coefficient.

BackInOut

Mirrored BackIn, using the coefficient directly without an extra multiplier.

Fields

overshoot: f64

Finite, nonnegative coefficient for each half.

ElasticOut

Exponentially damped oscillation, pinned at both endpoints.

Fields

amplitude: f64

Finite amplitude, at least one.

period: f64

Finite, strictly positive period in normalized time.

BounceOut

A piecewise quadratic outward bounce.

Steps(u32)

Right-continuous equal steps; the count must be nonzero.

CubicBezier

Unit-endpoint cubic Bezier, solving X before evaluating Y.

Fields

x1: f64

First X control, finite and in 0..=1.

y1: f64

First Y control, finite and allowed to overshoot.

x2: f64

Second X control, finite and in 0..=1.

y2: f64

Second Y control, finite and allowed to overshoot.

Custom(Arc<dyn Fn(f64) -> f64 + Send + Sync>)

A deterministic, thread-safe mapping with finite output. Input is clamped to 0..=1; callback endpoint values are preserved.

Implementations

impl Easing

pub fn apply(&self, progress: f64) -> f64

Evaluates normalized progress with double-precision math. Built-in transcendental operations use libm, not platform math routines.

Panics

Panics for invalid curve parameters, nonfinite progress or nonfinite output.

pub fn try_apply(&self, progress: f64) -> Result<f64, ValidationError>

Evaluates progress with recoverable parameter/output diagnostics. Panics raised inside a user callback still propagate unchanged.

pub fn reversed(self) -> Self

Converts an inward curve to its outward counterpart: 1 - f(1 - t). Invalid built-in parameters panic before the wrapper is constructed.

pub fn mirrored(self) -> Self

Uses the curve for acceleration and its reversal for deceleration. Invalid built-in parameters panic before the wrapper is constructed.

pub fn try_validate(&self) -> Result<(), ValidationError>

Checks built-in parameters without evaluating a custom callback.

Trait Implementations

impl Clone for Easing

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Easing

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

Formats the value using the given formatter.