How the horizontal extents of the columns of this table should be determined.
The FixedColumnWidth class can be used to specify a specific width in pixels. That is the cheapest way to size a table's columns.
The layout performance of the table depends critically on which column sizing algorithms are used here. In particular, IntrinsicColumnWidth is quite expensive because it needs to measure each cell in the column to determine the intrinsic size of the column.
The keys of this map (column indexes) are zero-based.
If this is set to null, then an empty map is assumed.