Struct Spring 

pub struct Spring { /* private fields */ }

A damped harmonic oscillator producing physically-based motion.

The spring interpolates from an initial position toward a target, with configurable stiffness and damping.

Example

use std::time::Duration;
use ftui_core::animation::spring::Spring;

let mut spring = Spring::new(0.0, 1.0)
    .with_stiffness(170.0)
    .with_damping(26.0);

// Simulate at 60fps
for _ in 0..120 {
    spring.tick(Duration::from_millis(16));
}

assert!((spring.position() - 1.0).abs() < 0.01);

Implementations

impl Spring

pub fn new(initial: f64, target: f64) -> Self

Create a spring starting at initial and targeting target.

Default parameters: stiffness = 170.0, damping = 26.0 (slightly underdamped, producing a subtle bounce).

pub fn normalized() -> Self

Create a spring animating from 0.0 to 1.0 (normalized).

pub fn with_stiffness(self, k: f64) -> Self

Set stiffness (builder pattern). Clamped to minimum 0.1.

pub fn with_damping(self, c: f64) -> Self

Set damping (builder pattern). Clamped to minimum 0.0.

pub fn with_rest_threshold(self, threshold: f64) -> Self

Set rest threshold (builder pattern).

pub fn with_velocity_threshold(self, threshold: f64) -> Self

Set velocity threshold (builder pattern).

pub fn position(&self) -> f64

Current position (unclamped).

pub fn velocity(&self) -> f64

Current velocity.

pub fn target(&self) -> f64

Current target.

pub fn stiffness(&self) -> f64

Stiffness parameter.

pub fn damping(&self) -> f64

Damping parameter.

pub fn set_target(&mut self, target: f64)

Change the target. Wakes the spring if it was at rest.

pub fn impulse(&mut self, velocity_delta: f64)

Apply an impulse (add to velocity). Wakes the spring.

pub fn is_at_rest(&self) -> bool

Whether the spring has settled at the target.

pub fn critical_damping(&self) -> f64

Compute the critical damping coefficient for the current stiffness.

At critical damping, the spring converges as fast as possible without oscillating.

pub fn advance(&mut self, dt: Duration)

Advance the spring by dt, subdividing if necessary for stability.

Trait Implementations

impl Animation for Spring

fn value(&self) -> f32

Returns the spring position clamped to [0.0, 1.0].

For springs with targets outside [0, 1], use position() directly.

fn tick(&mut self, dt: Duration)

Advance the animation by dt.

fn is_complete(&self) -> bool

Whether the animation has reached its end.

fn reset(&mut self)

Reset the animation to its initial state.

fn overshoot(&self) -> Duration

Time elapsed past completion. Used by composition types to forward remaining time (e.g., Sequence forwards overshoot from first to second). Returns Duration::ZERO for animations that never complete.

impl Clone for Spring

fn clone(&self) -> Spring

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Spring

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

Formats the value using the given formatter.