+@code{halign} is 0 for center, 2 for left, 4 for right, 6 for decimal,
+0xffffffad for mixed. For decimal alignment, @code{offset} is the
+decimal point's offset from the right side of the cell, in units of
+1/72 inch.
+
+@code{valign} specifies vertical alignment: 0 for center, 1 for top, 3
+for bottom.
+
+@code{left-margin}, @code{right-margin}, @code{top-margin}, and
+@code{bottom-margin} are in units of 1/72 inch.
+