Allocate a set of user-defined events, and return the beginning event
number for that set of events.
\param numevents the number of events to be allocated.
\returns the beginning event number, or 0 if numevents is invalid or if
there are not enough user-defined events left.
\threadsafety It is safe to call this function from any thread.
\since This function is available since SDL 3.2.0.
Allocate a set of user-defined events, and return the beginning event number for that set of events.
\param numevents the number of events to be allocated. \returns the beginning event number, or 0 if numevents is invalid or if there are not enough user-defined events left.
\threadsafety It is safe to call this function from any thread.
\since This function is available since SDL 3.2.0.
\sa SDL_PushEvent