Function getTween

esm/ScrollTrigger.js:871–906

(scrollTo, vars, initialValue, change1, change2)

      prop = "_scroll" + direction.p2,
      // add a tweenable property to the scroller that's a getter/setter function, like _scrollTop or _scrollLeft. This way, if someone does gsap.killTweensOf(scroller) it'll kill the scroll tween.
  getTween = function getTween(scrollTo, vars, initialValue, change1, change2) {
    var tween = getTween.tween,
        onComplete = vars.onComplete,
        modifiers = {};
    initialValue = initialValue || getScroll();

    var checkForInterruption = _interruptionTracker(getScroll, initialValue, function () {
      tween.kill();
      getTween.tween = 0;
    });

    change2 = change1 && change2 || 0; // if change1 is 0, we set that to the difference and ignore change2. Otherwise, there would be a compound effect.

    change1 = change1 || scrollTo - initialValue;
    tween && tween.kill();
    vars[prop] = scrollTo;
    vars.inherit = false;
    vars.modifiers = modifiers;

    modifiers[prop] = function () {
      return checkForInterruption(initialValue + change1 * tween.ratio + change2 * tween.ratio * tween.ratio);
    };

    vars.onUpdate = function () {
      _scrollers.cache++;
      getTween.tween && _updateAll(); // if it was interrupted/killed, like in a context.revert(), don't force an updateAll()
    };

    vars.onComplete = function () {
      getTween.tween = 0;
      onComplete && onComplete.call(tween);
    };

    tween = getTween.tween = gsap.to(scroller, vars);
    return tween;
  };

  scroller[prop] = getScroll;