Respring

An open-source implementation of SwiftUI's Spring animation.

This repository aims to provide an interface and behavior identical to SwiftUI's native Spring implementation. This package allows you to use Spring to drive your animations without depending on SwiftUI.

Usage

Swift

Use Spring to convert between different representations of spring parameters:

let spring = Spring(duration: 0.5, bounce: 0.3)
let (mass, stiffness, damping) = (spring.mass, spring.stiffness, spring.damping)
// (1.0, 157.9, 17.6)


let spring2 = Spring(mass: 1, stiffness: 100, damping: 10)
let (duration, bounce) = (spring2.duration, spring2.bounce)
// (0.63, 0.5)

You can also use it to query for a spring's position and its other properties for a given set of inputs:

func unitPosition(time: TimeInterval) -> Double {
    let spring = Spring(duration: 0.5, bounce: 0.3)
    return spring.position(target: 1.0, time: time)
}

Rust

The Rust implementation provides the same functionality with a similar API:

use respring::Spring;

let spring = Spring::with_duration_bounce(0.5, 0.3);
let (mass, stiffness, damping) = (spring.mass, spring.stiffness(), spring.damping());
// (1.0, 157.91367041742973, 17.59291886010284)

let spring2 = Spring::with_mass_stiffness_damping(1.0, 100.0, 10.0, false);
let (duration, bounce) = (spring2.duration(), spring2.bounce());
// (0.6283185307179586, 0.5)

Query for a spring's value and other properties for a given set of inputs:

fn unit_position(time: f64) -> f64 {
    let spring = Spring::with_duration_bounce(0.5, 0.3);
    // Using value method with target=1.0, initial_velocity=0.0
    spring.value(1.0, 0.0, time)
}

Both implementations also provide convenient preset springs:

// Rust
let smooth = Spring::smooth();     // No bounce
let snappy = Spring::snappy();     // Small bounce (0.15)
let bouncy = Spring::bouncy();     // Higher bounce (0.3)

// Swift  
let smooth = Spring.smooth         // No bounce
let snappy = Spring.snappy         // Small bounce (0.15)
let bouncy = Spring.bouncy         // Higher bounce (0.3)

Installation

Swift Package Manager

Adding Respring to the dependencies value of your Package.swift or the Package list in Xcode.

dependencies: [
    .package(url: "https://github.com/ktiays/Respring.git", from: "1.0.0")
]

Normally you'll want to depend on the Respring target:

.product(name: "Respring", package: "Respring")

Cargo (Rust)

Add this to your Cargo.toml:

[dependencies]
respring = "0.1.1"

Or install using cargo:

cargo add respring