def align(self):
        """Assures the previous window area is contained in the new one"""
        nofs = align_to_mmap(self.ofs, 0)
        self.size += self.ofs - nofs    # keep size constant
        self.ofs = nofs
        self.size = align_to_mmap(self.size, 1)
Assures the previous window area is contained in the new one