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

import raf from '../../_util/raf';
import isFF from '../utils/isFirefox';
import useOriginScroll from './useOriginScroll';
export default function useFrameWheel(inVirtual, isScrollAtTop, isScrollAtBottom, onWheelDelta) {
  var offsetRef = 0;
  var nextFrame = null;
  // Firefox patch
  var wheelValue = null;
  var isMouseScroll = false;
  // Scroll status sync
  var originScroll = useOriginScroll(isScrollAtTop, isScrollAtBottom);
  function onWheel(event) {
    if (!inVirtual.value) return;
    raf.cancel(nextFrame);
    var deltaY = event.deltaY;
    offsetRef += deltaY;
    wheelValue = deltaY;
    // Do nothing when scroll at the edge, Skip check when is in scroll
    if (originScroll(deltaY)) return;
    // Proxy of scroll events
    if (!isFF) {
      event.preventDefault();
    }
    nextFrame = raf(function () {
      // Patch a multiple for Firefox to fix wheel number too small
      // ref: https://github.com/ant-design/ant-design/issues/26372#issuecomment-679460266
      var patchMultiple = isMouseScroll ? 10 : 1;
      onWheelDelta(offsetRef * patchMultiple);
      offsetRef = 0;
    });
  }
  // A patch for firefox
  function onFireFoxScroll(event) {
    if (!inVirtual.value) return;
    isMouseScroll = event.detail === wheelValue;
  }
  return [onWheel, onFireFoxScroll];
}