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                <p>See <a href="">this</a> pen for it's use.</p>





if ('layoutWorklet' in CSS && 'registerLayout' in CSS) {
  registerLayout('masonry', class {
    static get inputProperties() {
      return ['--masonry-gap', '--masonry-columns', '--masonry-column-max-width'];

    async layout(children, edges, constraints, styleMap, breakToken) {
      const inlineSize = constraints.fixedInlineSize;

      const gap = parseInt(styleMap.get('--masonry-gap'));
      const columnValue = styleMap.get('--masonry-columns');
      const columnWidth = parseInt(styleMap.get('--masonry-column-max-width'));

      // We also accept 'auto', which will select the BEST number of columns.
      const columns = (() => {
        if (columnValue == 'auto') return Math.ceil(inlineSize / columnWidth);
        else return parseInt(columnValue);

      // Layout all children with simply their column size.
      const childInlineSize = (inlineSize - ((columns + 1) * gap)) / columns;
      const childFragments = await => {
        return child.layoutNextFragment({fixedInlineSize: childInlineSize});

      let autoBlockSize = 0;
      const columnOffsets = Array(columns).fill(0);
      for (let childFragment of childFragments) {
        // Select the column with the least amount of stuff in it.
        const min = columnOffsets.reduce((acc, val, idx) => {
          if (!acc || val < acc.val) {
            return {idx, val};

          return acc;
        }, {val: Infinity, idx: -1});

        childFragment.inlineOffset = gap + (childInlineSize + gap) * min.idx;
        childFragment.blockOffset = gap + min.val;

        columnOffsets[min.idx] = childFragment.blockOffset + childFragment.blockSize;
        autoBlockSize = Math.max(autoBlockSize, columnOffsets[min.idx] + gap);

      return {autoBlockSize, childFragments};