shuiwu/node_modules/ant-design-vue/es/vc-virtual-list/hooks/useOriginScroll.js

export default (function (isScrollAtTop, isScrollAtBottom) {
  // Do lock for a wheel when scrolling
  var lock = false;
  var lockTimeout = null;
  function lockScroll() {
    clearTimeout(lockTimeout);
    lock = true;
    lockTimeout = setTimeout(function () {
      lock = false;
    }, 50);
  }
  return function (deltaY) {
    var smoothOffset = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : false;
    var originScroll =
    // Pass origin wheel when on the top
    deltaY < 0 && isScrollAtTop.value ||
    // Pass origin wheel when on the bottom
    deltaY > 0 && isScrollAtBottom.value;
    if (smoothOffset && originScroll) {
      // No need lock anymore when it's smooth offset from touchMove interval
      clearTimeout(lockTimeout);
      lock = false;
    } else if (!originScroll || lock) {
      lockScroll();
    }
    return !lock && originScroll;
  };
});