Function scrollArray

scripts/smoothScroll.js:309–401

* Pushes scroll actions to the scrolling queue.

(elem, left, top)

   * Pushes scroll actions to the scrolling queue.
   */
  function scrollArray(elem, left, top) {
    directionCheck(left, top);
    if (options.accelerationMax != 1) {
      let now = dateNow();
      let elapsed = now - lastScroll;
      if (elapsed < options.accelerationDelta) {
        let factor = (1 + 50 / elapsed) / 2;
        if (factor > 1) {
          factor = Math.min(factor, options.accelerationMax);
          left *= factor;
          top *= factor;
        }
      }
      lastScroll = dateNow();
    }
    // push a scroll command
    que.push({
      x: left,
      y: top,
      lastX: left < 0 ? 0.99 : -0.99,
      lastY: top < 0 ? 0.99 : -0.99,
      start: dateNow(),
    });
    // don't act if there's a pending frame loop
    if (pending) {
      return;
    }
    let scrollRoot = getScrollRoot();
    let isWindowScroll = elem === scrollRoot || elem === document.body;
    // if we haven't already fixed the behavior,
    // and it needs fixing for this sesh
    if (elem.$scrollBehavior == null && isScrollBehaviorSmooth(elem)) {
      elem.$scrollBehavior = elem.style.scrollBehavior;
      elem.style.scrollBehavior = "auto";
    }
    let step = function (time) {
      let now = dateNow();
      let scrollX = 0;
      let scrollY = 0;
      for (let i = 0; i < que.length; i++) {
        let item = que[i];
        let elapsed = now - item.start;
        let finished = elapsed >= options.animationTime;
        // scroll position: [0, 1]
        let position = finished ? 1 : elapsed / options.animationTime;
        // easing [optional]
        if (options.pulseAlgorithm) {
          position = pulse(position);
        }
        // only need the difference
        let x = (item.x * position - item.lastX) >> 0;
        let y = (item.y * position - item.lastY) >> 0;
        // add this to the total scrolling
        scrollX += x;
        scrollY += y;
        // update last values
        item.lastX += x;
        item.lastY += y;