The width of the cells of a text table is defined by the position
of the separator between neighboring cells.
If cells of the table are merged, this separator is not removed, but
it is hidden.
A text table or a text table row provides the separators in a
sequence of TableColumnSeparators. If the table only
consists of one column, then this sequence is empty.
The real width of a table depends on the environment (page style and
number of text columns at the table's position, alignment, and left and
right margins). For that reason, the table column separator does not
contain metric values for the column widths. The values are relative
to the value of the property TextTable::TableColumnRelativeSum.
A table provides this property only if all rows have the same structure.
If the table does not provide the property, then it cannot be set using.
The state of IsVisible and the
count of the sequence must be the same in as it was in.
Hidden separators cannot be moved and they cannot be overtaken by visible
separators.
