jnpf-web-vue3/node_modules/ant-design-vue/es/vc-virtual-list/hooks/useScrollTo.js

import raf from '../../_util/raf';
export default function useScrollTo(containerRef, mergedData, heights, props, getKey, collectHeight, syncScrollTop, triggerFlash) {
  let scroll;
  return arg => {
    // When not argument provided, we think dev may want to show the scrollbar
    if (arg === null || arg === undefined) {
      triggerFlash();
      return;
    }
    // Normal scroll logic
    raf.cancel(scroll);
    const data = mergedData.value;
    const itemHeight = props.itemHeight;
    if (typeof arg === 'number') {
      syncScrollTop(arg);
    } else if (arg && typeof arg === 'object') {
      let index;
      const {
        align
      } = arg;
      if ('index' in arg) {
        ({
          index
        } = arg);
      } else {
        index = data.findIndex(item => getKey(item) === arg.key);
      }
      const {
        offset = 0
      } = arg;
      // We will retry 3 times in case dynamic height shaking
      const syncScroll = (times, targetAlign) => {
        if (times < 0 || !containerRef.value) return;
        const height = containerRef.value.clientHeight;
        let needCollectHeight = false;
        let newTargetAlign = targetAlign;
        // Go to next frame if height not exist
        if (height) {
          const mergedAlign = targetAlign || align;
          // Get top & bottom
          let stackTop = 0;
          let itemTop = 0;
          let itemBottom = 0;
          const maxLen = Math.min(data.length, index);
          for (let i = 0; i <= maxLen; i += 1) {
            const key = getKey(data[i]);
            itemTop = stackTop;
            const cacheHeight = heights.get(key);
            itemBottom = itemTop + (cacheHeight === undefined ? itemHeight : cacheHeight);
            stackTop = itemBottom;
            if (i === index && cacheHeight === undefined) {
              needCollectHeight = true;
            }
          }
          const scrollTop = containerRef.value.scrollTop;
          // Scroll to
          let targetTop = null;
          switch (mergedAlign) {
            case 'top':
              targetTop = itemTop - offset;
              break;
            case 'bottom':
              targetTop = itemBottom - height + offset;
              break;
            default:
              {
                const scrollBottom = scrollTop + height;
                if (itemTop < scrollTop) {
                  newTargetAlign = 'top';
                } else if (itemBottom > scrollBottom) {
                  newTargetAlign = 'bottom';
                }
              }
          }
          if (targetTop !== null && targetTop !== scrollTop) {
            syncScrollTop(targetTop);
          }
        }
        // We will retry since element may not sync height as it described
        scroll = raf(() => {
          if (needCollectHeight) {
            collectHeight();
          }
          syncScroll(times - 1, newTargetAlign);
        }, 2);
      };
      syncScroll(5);
    }
  };
}