How do you Get the Unity Launcher to Autohide underneath other windows while not autohiding when all Windows are un-maximised?

view story

http://askubuntu.com – That is suppose you have google chrome open or some other program how can we get the unity launcher to autohide when it (the program) is open and maximised but to reappear when it's unmaximised (i.e. it doesn't cover the entire desktop). I am running 12.10 (HowTos)