In SDL2, when is SDL_JoystickInstanceID different than SDL_JoystickOpen(n)?

Question

In SDL2 the documentation suggests that the number used to open the joystick (between 0 and SDL_NumJoysticks()) can be different than the SDL_JoystickID which; used to reference the stick in events. When are these numbers different?

Answer 1

Code should assume the numbers are always different (even if they happen to be the same sometimes). For example, when you get a SDL_ControllerAxisEvent, the which field should match the value of SDL_JoystickInstanceID() for one of your open joystick handles. You can use SDL_JoystickFromInstanceID() to get the joystick handle from the which value.