@nativescript-community/ui-persistent-bottomsheet/VelocityTracker.js

NativeScript plugin that allows you to easily add a persistent bottomsheet to your projects.

export class VelocityTracker {
    constructor() {
        this.samples = [];
        this.vx = 0;
        this.vy = 0;
        this.maxAgeMs = 300;
        this.maxVelocity = Infinity;
    }
    static obtain() {
        return new VelocityTracker();
    }
    recycle() {
        this.samples.length = 0;
    }
    addMovement(x, y, time) {
        const t = time ?? performance.now();
        this.samples.push({ x, y, t });
        // drop old samples
        while (this.samples.length && t - this.samples[0].t > this.maxAgeMs) {
            this.samples.shift();
        }
    }
    computeCurrentVelocity(units = 1000, maxVelocity = Infinity) {
        this.maxVelocity = maxVelocity;
        if (this.samples.length < 2) {
            this.vx = 0;
            this.vy = 0;
            return;
        }
        let sumW = 0;
        let sumVX = 0;
        let sumVY = 0;
        const newestTime = this.samples[this.samples.length - 1].t;
        for (let i = 1; i < this.samples.length; i++) {
            const a = this.samples[i - 1];
            const b = this.samples[i];
            const dt = (b.t - a.t) / 1000;
            if (dt <= 0)
                continue;
            const age = newestTime - b.t;
            const w = Math.max(0.1, 1 - age / this.maxAgeMs);
            sumW += w;
            sumVX += (w * (b.x - a.x)) / dt;
            sumVY += (w * (b.y - a.y)) / dt;
        }
        this.vx = this.clamp((sumVX / sumW) * (units / 1000));
        this.vy = this.clamp((sumVY / sumW) * (units / 1000));
    }
    getXVelocity() {
        return this.vx;
    }
    getYVelocity() {
        return this.vy;
    }
    clamp(v) {
        return Math.max(-this.maxVelocity, Math.min(this.maxVelocity, v));
    }
}
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