'iterates over possible grids given a number of windows'

def _possible_grids(self, num_windows):

    if (num_windows < 2):
        end = 2
    else:
        end = ((num_windows // 2) + 1)
    for rows in range(1, end):
        cols = int(math.ceil((num_windows / rows)))
        (yield (rows, cols, ROWCOL))
        if (rows != cols):
            (yield (cols, rows, COLROW))
