Apply overflow, justification, padding and expansion to a row.

def format_row_filter(self, next_filter):
        """ Apply overflow, justification, padding and expansion to a row. """
        next(next_filter)
        while True:
            items = (yield)
            assert all(isinstance(x, VTMLBuffer) for x in items)
            raw = (fn(x) for x, fn in zip(items, self.formatters))
            for x in itertools.zip_longest(*raw):
                next_filter.send(x)