Include file for SDL joystick event handling
The term "device_index" identifies currently plugged in joystick devices between 0 and SDL_NumJoysticks(), with the exact joystick behind a device_index changing as joysticks are plugged and unplugged.
The term "instance_id" is the current instantiation of a joystick device in the system, if the joystick is removed and then re-inserted then it will get a new instance_id, instance_id's are monotonically increasing identifiers of a joystick plugged in.
The term "player_index" is the number assigned to a player on a specific controller. For XInput controllers this returns the XInput user index. Many joysticks will not be able to supply this information.
The term JoystickGUID is a stable 128-bit identifier for a joystick device that does not change over time, it identifies class of the device (a X360 wired controller for example). This identifier is platform dependent.