Provided by: libsdl3-doc_3.2.20+ds-2_all 

NAME
SDL_NSTimerCallback - Function prototype for the nanosecond timer callback function.
SYNOPSIS
#include <SDL3/SDL_timer.h>
typedef Uint64 (SDLCALL *SDL_NSTimerCallback)(void *userdata, SDL_TimerID timerID, Uint64 interval);
DESCRIPTION
The callback function is passed the current timer interval and returns the next timer interval, in
nanoseconds. If the returned value is the same as the one passed in, the periodic alarm continues,
otherwise a new alarm is scheduled. If the callback returns 0, the periodic alarm is canceled and will be
removed.
FUNCTION PARAMETERS
userdata
an arbitrary pointer provided by the app through SDL_AddTimer, for its own use.
timerID
the current timer being processed.
interval
the current callback time interval.
RETURN VALUE
Returns the new callback time interval, or 0 to disable further runs of the callback.
THREAD SAFETY
SDL may call this callback at any time from a background thread; the application is responsible for
locking resources the callback touches that need to be protected.
AVAILABILITY
This datatype is available since SDL 3.2.0.
SEE ALSO
SDL_AddTimerNS(3)
Simple Directmedia Layer SDL 3.2.20 SDL_NSTimerCallback(3type)