get-filename in frame:basic<%>

This returns the filename that the frame is currently being saved as, or #f if there is no appropriate filename.

• (send a-frame:basic get-filename temp) -> (union #f string)
     temp = #f : (union #f (box boolean))

  Defaultly returns #f.

  If temp is a box, it is filled with #t or #f, depending if the filename is a temporary filename.