afwlehmann

Sorry for re-opening, but it turns out that the current interval is indeed not updated. I've just checked the source code of the 2.0.3 release again:

   163	    if (current->canceled) {
   164	        interval = 0;
   165	    } else {
   166	        interval = current->callback(current->interval, current->param);
   167	    }
   168
   169	    if (interval > 0) {
   170	        /* Reschedule this timer */
   171	        current->interval = interval; // <-- this line is missing
   172	        current->scheduled = tick + interval;
   173	        SDL_AddTimerInternal(data, current);
   174	    } else {

According to the documentation: "The callback function is passed the current timer interval and the user supplied parameter from the SDL_AddTimer() call and returns the next timer interval. If the returned value from the callback is 0, the timer is canceled."

If I understand the text correctly, then the current interval should in fact be updated according to the returned value. Otherwise there would be a discrepancy between the next time for which the timer is actually re-scheduled and the value that's passed to the callback once the timer fires again.

This could be fixed by adding line #171.