@mui/x-data-grid/modern/hooks/features/columns/useGridColumnSpanning.js

The Community plan edition of the Data Grid components (MUI X).

import * as React from 'react';
import { useGridApiMethod } from '../../utils/useGridApiMethod';
import { useGridApiEventHandler } from '../../utils/useGridApiEventHandler';
/**
 * @requires useGridColumns (method, event)
 * @requires useGridParamsApi (method)
 */
export const useGridColumnSpanning = apiRef => {
  const lookup = React.useRef({});
  const getCellColSpanInfo = (rowId, columnIndex) => {
    return lookup.current[rowId]?.[columnIndex];
  };

  // Calculate `colSpan` for each cell in the row
  const calculateColSpan = React.useCallback(({
    rowId,
    minFirstColumn,
    maxLastColumn,
    columns
  }) => {
    for (let i = minFirstColumn; i < maxLastColumn; i += 1) {
      const cellProps = calculateCellColSpan({
        apiRef,
        lookup: lookup.current,
        columnIndex: i,
        rowId,
        minFirstColumnIndex: minFirstColumn,
        maxLastColumnIndex: maxLastColumn,
        columns
      });
      if (cellProps.colSpan > 1) {
        i += cellProps.colSpan - 1;
      }
    }
  }, [apiRef]);
  const columnSpanningPublicApi = {
    unstable_getCellColSpanInfo: getCellColSpanInfo
  };
  const columnSpanningPrivateApi = {
    calculateColSpan
  };
  useGridApiMethod(apiRef, columnSpanningPublicApi, 'public');
  useGridApiMethod(apiRef, columnSpanningPrivateApi, 'private');
  const handleColumnReorderChange = React.useCallback(() => {
    // `colSpan` needs to be recalculated after column reordering
    lookup.current = {};
  }, []);
  useGridApiEventHandler(apiRef, 'columnOrderChange', handleColumnReorderChange);
};
function calculateCellColSpan(params) {
  const {
    apiRef,
    lookup,
    columnIndex,
    rowId,
    minFirstColumnIndex,
    maxLastColumnIndex,
    columns
  } = params;
  const columnsLength = columns.length;
  const column = columns[columnIndex];
  const row = apiRef.current.getRow(rowId);
  const value = apiRef.current.getRowValue(row, column);
  const colSpan = typeof column.colSpan === 'function' ? column.colSpan(value, row, column, apiRef) : column.colSpan;
  if (!colSpan || colSpan === 1) {
    setCellColSpanInfo(lookup, rowId, columnIndex, {
      spannedByColSpan: false,
      cellProps: {
        colSpan: 1,
        width: column.computedWidth
      }
    });
    return {
      colSpan: 1
    };
  }
  let width = column.computedWidth;
  for (let j = 1; j < colSpan; j += 1) {
    const nextColumnIndex = columnIndex + j;
    // Cells should be spanned only within their column section (left-pinned, right-pinned and unpinned).
    if (nextColumnIndex >= minFirstColumnIndex && nextColumnIndex < maxLastColumnIndex) {
      const nextColumn = columns[nextColumnIndex];
      width += nextColumn.computedWidth;
      setCellColSpanInfo(lookup, rowId, columnIndex + j, {
        spannedByColSpan: true,
        rightVisibleCellIndex: Math.min(columnIndex + colSpan, columnsLength - 1),
        leftVisibleCellIndex: columnIndex
      });
    }
    setCellColSpanInfo(lookup, rowId, columnIndex, {
      spannedByColSpan: false,
      cellProps: {
        colSpan,
        width
      }
    });
  }
  return {
    colSpan
  };
}
function setCellColSpanInfo(lookup, rowId, columnIndex, cellColSpanInfo) {
  if (!lookup[rowId]) {
    lookup[rowId] = {};
  }
  lookup[rowId][columnIndex] = cellColSpanInfo;
}