Get a pointer to the user data for the current music hook.
Defined in <SDL_mixer.h>
void * Mix_GetMusicHookData(void);
(void *) Returns pointer to the user data previously passed to Mix_HookMusic.
This returns the arg
pointer last passed to Mix_HookMusic(), or NULL if that function has never been called.
This function is available since SDL_mixer 2.0.0.