@shopify/react-native-skia/lib/commonjs/animation/spring/functions/spring.js

High-performance React Native Graphics using Skia

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.createSpringEasing = void 0;

/**
 * @description Returns a cached jsContext function for a spring with duration
 * @param mass The mass of the spring
 * @param stiffness The stiffness of the spring
 * @param damping Spring damping
 * @param velocity The initial velocity
 */
const createSpringEasing = params => {
  const config = {
    mass: 1,
    stiffness: 100,
    damping: 10,
    velocity: 0,
    ...params
  };
  config.velocity /= 100;
  return getSpringEasing(config);
};

exports.createSpringEasing = createSpringEasing;

const getSpringEasing = config => {
  const {
    stiffness,
    mass,
    damping,
    velocity: initialVelocity
  } = config; // Setup spring state

  const state = {
    w0: Math.sqrt(stiffness / mass),
    zeta: 0,
    wd: 0,
    a: 1,
    b: 0
  };
  state.zeta = damping / (2 * Math.sqrt(stiffness * mass));
  state.wd = state.zeta < 1 ? state.w0 * Math.sqrt(1 - state.zeta * state.zeta) : 0;
  state.a = 1;
  state.b = state.zeta < 1 ? (state.zeta * state.w0 + -initialVelocity) / state.wd : -initialVelocity + state.w0;

  const update = (t, duration) => {
    let progress = duration ? duration * t / 1000 : t;

    if (state.zeta < 1) {
      progress = Math.exp(-progress * state.zeta * state.w0) * (state.a * Math.cos(state.wd * progress) + state.b * Math.sin(state.wd * progress));
    } else {
      progress = (state.a + state.b * progress) * Math.exp(-progress * state.w0);
    }

    if (t === 0 || t === 1) {
      return t;
    }

    return 1 - progress;
  };

  const getDurationMs = () => {
    var frame = 1 / 6;
    var elapsed = 0;
    var rest = 0;

    while (true) {
      elapsed += frame;

      if (update(elapsed) === 1) {
        rest++;

        if (rest >= 6) {
          break;
        }
      } else {
        rest = 0;
      }
    }

    var durationMs = elapsed * frame * 1000;
    return durationMs + 1000;
  };

  const durationMs = getDurationMs();
  return {
    easing: t => update(t, durationMs),
    duration: durationMs
  };
};
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