It is not clear to me what your code should achieve and demonstrate.
IMO it's no good idea to do "sdltk root 0 0" arbitrarily since you
didn't change the root window anyway. Also there are lots of redundant
"wm attribute . -fullscreen", and so on. Finally, things are device
dependent, at least to make it more complicated. On my 10" tablet
(after removing the aforementioned things), it works. However, it's
not exactly brand new and reports API 19.