NewState creates a state object for tracking keyboard state.

Up checks.

called "Command" on OS X.

AllKeys is the set of all defined key codes.

Down is sent when a key is pressed.

Held is sent when a key is held down.

Up is sent when a key is released.

A State tracks what keys of a keyboard are currently pressed and for how long they have been pressed if they are held down.

Code is the identity of a key relative to a notional "standard" keyboard.

An Event is sent as the payload for all key bindings.