Method getItemSizeAndItemsPerRow

src/react-list.js:241–275

()

  }

  getItemSizeAndItemsPerRow() {
    const { axis, useStaticSize } = this.props;
    let { itemSize, itemsPerRow } = this.state;
    if (useStaticSize && itemSize && itemsPerRow) {
      return { itemSize, itemsPerRow };
    }

    const itemEls = this.items.children;
    if (!itemEls.length) return {};

    const firstEl = itemEls[0];

    // Firefox has a problem where it will return a *slightly* (less than
    // thousandths of a pixel) different size for the same element between
    // renders. This can cause an infinite render loop, so only change the
    // itemSize when it is significantly different.
    const firstElSize = firstEl[OFFSET_SIZE_KEYS[axis]];
    const delta = Math.abs(firstElSize - itemSize);
    if (isNaN(delta) || delta >= 1) itemSize = firstElSize;

    if (!itemSize) return {};

    const startKey = OFFSET_START_KEYS[axis];
    const firstStart = firstEl[startKey];
    itemsPerRow = 1;
    for (
      let item = itemEls[itemsPerRow];
      item && item[startKey] === firstStart;
      item = itemEls[itemsPerRow]
    ) {
      ++itemsPerRow;
    }

    return { itemSize, itemsPerRow };
  }

  clearSizeCache() {
    this.cachedScrollPosition = null;