[guitarbug]

guitarbug, I don't know about the "root part" of your question because my box is rooted but 13 does indeed play in full screen.

john,
thanks for your comments.
my TV box is amlogic8726-mx based and come with android 4.2.2,i did not find a way to root it,so i must run xbmc in my un-rooted box.
actually,after box startup,when i play a video the first time ,xbmc 13 can in full screen,
but if i watch some online video, then use xbmc to play video,xbmc 13 can not in full screen anymore,unless i reboot the box.
with the same reproduce steps,xbmc 12 did not get this issue.

the key point of this issue in xbmc13 is:
if you always use xbmc play video,it's all fine,full screen always.
BUT,if you play some video use other player(such as the player come with android),then use xbmc to play video ,the issue happening.
did someone get same issue?