3 * Screens - full-screen dialogs
5 * These compose the first level of interaction in the UI.
7 * There is always exactly one active screen, which is in
8 * control of the entire display on which it is displayed.
10 * Screen activations are stacked, providing interaction depth.
15 void (*on_enter)(void);
16 void (*on_leave)(void);
17 void (*on_render)(void);
18 void (*on_key_press)(void);
19 void (*on_key_release)(void);