two finger.js

* ASCII text
"use strict";

function NormalizeVector(v) {
    const l = 1 / (v.x * v.x + v.y + v.y);
    v.x *= l; v.y *= l;
    return v;
}

function GetAngleBetweenVectors(pre, cur) {
    const ceta = Math.acos(pre.x * cur.x + pre.y * cur.y);
    return Math.min(ceta, Math.PI - ceta); // NOTE: Positive number
}

module.export = class TwoFinger {

    TwoFinger() {
        this.preVec2D = { x: 0, y: 0 };
        this.callbacks = new Array();
    }

    RegisterEvent(callback) {
        this.callbacks.push(callback);
    }

    UnregisterEvent(callback) {
        this.callbacks.remove(callback);
    }

    Update(x1, y1, x2, y2) {
        const curVec2D = NormalizeVector({ x: x2 - x1, y: y2 - y1 }); // NOTE: Noralized vector
        const ceta = GetAngleBetweenVectors(this.preVec2D, curVec2D);
        // TODO: update model rotaion
        // const EPSILON = 0.0314;
        // if (ceta > EPSILON) {
        //  this.callbacks.forEach(callback => callback(ceta));
        // }

        this.preVec2D = curVec2D;
    }

};