I don't know if it works on all apps., but on some ' esc ' will bring you back to normal view. That's assuming, of course, that you still have any control of the app. Maybe it's because i'm running Gnome in the background of XFCE - for dependencies - but ctrl-alt-backspace works to bail out to the loging screen
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Desktop #1 F18
Desktop #2 Mint 14
Laptop: Macpup 529
Netbook: Debian ARM