type SDL_USEREVENT through to SDL_NUMEVENTS-1
code User defined event code
data1 User defined data pointer
data2 User defined data pointer
SDL_UserEvent is in the user member of the structure SDL_Event. This event is unique, it is never created by
SDL but only by the user. The event can be pushed onto the event queue using SDL_PushEvent. The contents of
the structure members or completely up to the programmer, the only requirement is that type is a value from
SDL_USEREVENT to SDL_NUMEVENTS-1 (inclusive).