prosperon/scripts/tween.js

/* Take numbers from 0 to 1 and remap them to easing functions */
var Ease = {
  linear(t) {
    return t;
  },

  in(t) {
    return t * t;
  },

  out(t) {
    var d = 1 - t;
    return 1 - d * d;
  },

  inout(t) {
    var d = -2 * t + 2;
    return t < 0.5 ? 2 * t * t : 1 - (d * d) / 2;
  },
};

function make_easing_fns(num) {
  var obj = {};

  obj.in = function (t) {
    return Math.pow(t, num);
  };

  obj.out = function (t) {
    return 1 - Math.pow(1 - t, num);
  };

  var mult = Math.pow(2, num - 1);

  obj.inout = function (t) {
    return t < 0.5 ? mult * Math.pow(t, num) : 1 - Math.pow(-2 * t + 2, num) / 2;
  };

  return obj;
}

Ease.quad = make_easing_fns(2);
Ease.cubic = make_easing_fns(3);
Ease.quart = make_easing_fns(4);
Ease.quint = make_easing_fns(5);

Ease.expo = {
  in(t) {
    return t === 0 ? 0 : Math.pow(2, 10 * t - 10);
  },

  out(t) {
    return t === 1 ? 1 : 1 - Math.pow(2, -10 * t);
  },

  inout(t) {
    return t === 0 ? 0 : t === 1 ? 1 : t < 0.5 ? Math.pow(2, 20 * t - 10) / 2 : (2 - Math.pow(2, -20 * t + 10)) / 2;
  },
};

Ease.bounce = {
  in(t) {
    return 1 - this.out(t - 1);
  },

  out(t) {
    var n1 = 7.5625;
    var d1 = 2.75;

    if (t < 1 / d1) {
      return n1 * t * t;
    } else if (t < 2 / d1) {
      return n1 * (t -= 1.5 / d1) * t + 0.75;
    } else if (t < 2.5 / d1) {
      return n1 * (t -= 2.25 / d1) * t + 0.9375;
    } else return n1 * (t -= 2.625 / d1) * t + 0.984375;
  },

  inout(t) {
    return t < 0.5 ? (1 - this.out(1 - 2 * t)) / 2 : (1 + this.out(2 * t - 1)) / 2;
  },
};

Ease.sine = {
  in(t) {
    return 1 - Math.cos((t * Math.PI) / 2);
  },

  out(t) {
    return Math.sin((t * Math.PI) / 2);
  },

  inout(t) {
    return -(Math.cos(Math.PI * t) - 1) / 2;
  },
};

Ease.elastic = {
  in(t) {
    return t === 0 ? 0 : t === 1 ? 1 : -Math.pow(2, 10 * t - 10) * Math.sin((t * 10 - 10.75) * this.c4);
  },

  out(t) {
    return t === 0 ? 0 : t === 1 ? 1 : Math.pow(2, -10 * t) * Math.sin((t * 10 - 0.75) * this.c4) + 1;
  },

  inout(t) {
    t === 0 ? 0 : t === 1 ? 1 : t < 0.5 ? -(Math.pow(2, 20 * t - 10) * Math.sin((20 * t - 11.125) * this.c5)) / 2 : (Math.pow(2, -20 * t + 10) * Math.sin((20 * t - 11.125) * this.c5)) / 2 + 1;
  },
};

Ease.elastic.c4 = (2 * Math.PI) / 3;
Ease.elastic.c5 = (2 * Math.PI) / 4.5;

var tween = function (from, to, time, fn, endfn) {
  var start = profile.secs(profile.now());
  var update = function (dt) {
    profile.report("tween");
    var elapsed = profile.secs(profile.now()) - start;
    fn(from.lerp(to, elapsed / time));
    if (elapsed >= time) {
      fn(to);
      if (stop.then) stop.then();
      stop();
      endfn?.();
    }
    profile.endreport("tween");
  };
  var stop = Register.update.register(update);
  return stop;
};

var Tween = {
  default: {
    loop: "hold",
    /*
      loop types
      none: when done, return to first value
      hold: hold last value of tween
      restart: restart at beginning, looping
      yoyo: go up and then back down
      circle: go up and back down, looped
    */
    time: 1 /* seconds to do */,
    ease: Ease.linear,
    whole: true /* True if time is for the entire tween, false if each stage */,
    cb: function () {},
  },

  start(obj, target, tvals, options) {
    var defn = Object.create(this.default);
    Object.assign(defn, options);

    if (defn.loop === "circle") tvals.push(tvals[0]);
    else if (defn.loop === "yoyo") {
      for (var i = tvals.length - 2; i >= 0; i--) tvals.push(tvals[i]);
    }

    defn.accum = 0;

    var slices = tvals.length - 1;
    var slicelen = 1 / slices;

    defn.fn = function (dt) {
      defn.accum += dt;
      if (defn.accum >= defn.time && defn.loop === "hold") {
        if (typeof target === "string") obj[target] = tvals[tvals.length - 1];
        else target(tvals[tvals.length - 1]);

        defn.pause();
        defn.cb.call(obj);
        return;
      }

      defn.pct = (defn.accum % defn.time) / defn.time;
      if (defn.loop === "none" && defn.accum >= defn.time) defn.stop();

      var t = defn.whole ? defn.ease(defn.pct) : defn.pct;

      var nval = t / slicelen;
      var i = Math.trunc(nval);
      nval -= i;

      if (!defn.whole) nval = defn.ease(nval);

      if (typeof target === "string") obj[target] = tvals[i].lerp(tvals[i + 1], nval);
      else target(tvals[i].lerp(tvals[i + 1], nval));
    };

    var playing = false;

    defn.play = function () {
      if (playing) return;
      defn._end = Register.update.register(defn.fn.bind(defn));
      playing = true;
    };
    defn.restart = function () {
      defn.accum = 0;
      if (typeof target === "string") obj[target] = tvals[0];
      else target(tvals[0]);
    };
    defn.stop = function () {
      if (!playing) return;
      defn.pause();
      defn.restart();
    };
    defn.pause = function () {
      defn._end();
      if (!playing) return;

      playing = false;
    };

    return defn;
  },
};

Tween.make = Tween.start;

return { Tween, Ease, tween };