The SL class is for the statusbar (Status Line). This is generally where the game name and score is written.
If the code property is set, it calls the code's doit() method, and if the sttate property is ENABLED, draws the statusbar, otherwise, it hides it.
Enables the statusbar and updates it (calling it's doit() method).
Disables the statusbar and updates it (calling it's doit() method).