List computeColumnWidths()

in packages/devtools_app/lib/src/shared/table.dart [133:214]
61 lines of code
21 McCabe index (conditional complexity)

  List<double> computeColumnWidths(double maxWidth) {
    // Subtract width from outer padding around table.
    maxWidth -= 2 * defaultSpacing;
    maxWidth -= widget.numSpacers * defaultSpacing;
    maxWidth = max(0, maxWidth);

    double available = maxWidth;
    // Columns sorted by increasing minWidth.
    final sortedColumns = widget.columns.toList()
      ..sort((a, b) {
        if (a.minWidthPx != null && b.minWidthPx != null) {
          return a.minWidthPx.compareTo(b.minWidthPx);
        }
        if (a.minWidthPx != null) return -1;
        if (b.minWidthPx != null) return 1;
        return 0;
      });

    for (var col in widget.columns) {
      if (col.fixedWidthPx != null) {
        available -= col.fixedWidthPx;
      } else if (col.minWidthPx != null) {
        available -= col.minWidthPx;
      }
    }
    available = max(available, 0);
    int unconstrainedCount = 0;
    for (var column in sortedColumns) {
      if (column.fixedWidthPx == null && column.minWidthPx == null) {
        unconstrainedCount++;
      }
    }

    if (available > 0) {
      // We need to find how many columns with minWidth constraints can actually
      // be treated as unconstrained as their minWidth constraint is satisfied
      // by the width given to all unconstrained columns.
      // We use a greedy algorithm to accurately compute this by iterating
      // through the columns from the smallest minWidth to largest minWidth
      // incrementally adding columns where the minWidth constraint can be
      // satisfied using the width given to unconstrained columns.
      for (var column in sortedColumns) {
        if (column.fixedWidthPx == null && column.minWidthPx != null) {
          // Width of this column if it was not clamped to its min width.
          // We add column.minWidthPx to the available width because
          // available is currently not considering the space reserved for this
          // column's min width as available.
          final widthIfUnconstrainedByMinWidth =
              (available + column.minWidthPx) / (unconstrainedCount + 1);
          if (widthIfUnconstrainedByMinWidth < column.minWidthPx) {
            // We have found the first column that will have to be clamped to
            // its min width.
            break;
          }
          // As this column's width in the final layout is greater than its
          // min width, we can treat it as unconstrained and give its min width
          // back to the available pool.
          unconstrainedCount++;
          available += column.minWidthPx;
        }
      }
    }
    final unconstrainedWidth =
        unconstrainedCount > 0 ? available / unconstrainedCount : available;
    int unconstrainedFound = 0;
    final widths = <double>[];
    for (ColumnData<T> column in widget.columns) {
      double width = column.fixedWidthPx;
      if (width == null) {
        if (column.minWidthPx != null &&
            column.minWidthPx > unconstrainedWidth) {
          width = column.minWidthPx;
        } else {
          width = unconstrainedWidth;
          unconstrainedFound++;
        }
      }
      widths.add(width);
    }
    assert(unconstrainedCount == unconstrainedFound);
    return widths;
  }