SDL2/C frame limiter

framelimit.c

// From: https://cplusplus.com/forum/beginner/94946/
// By: https://cplusplus.com/user/Disch/


#define FPS 60

int frame_length = 1000 / FPS;    // Number of ms between frames. 17 gives you approx 60 FPS  (1000 / 60)
Uint32 next_frame;                // Timestamp that next frame is to occur
int skipped_frames;               // Number of frames we have skipped

// Configurable (optionally const) value to determine when to start "skipping" frames.
// I.e., we'll start skipping after we fall this many frames behind
int skip_frames_behind = 5;

// Configurable (optionally const) value to determine how many frames we allow it to
// "fall behind" before we give up and resync.
// Higher values = Game opts to run 'slower'
// Lower values = Game opts to run 'choppier'
int max_frame_skip = 5;

void sdl_frame_limit(void (*fn)(bool)) {
  Sint32 delta = (Sint32) (SDL_GetTicks() - next_frame);    // get time between next frame and now

  if (delta < 0) {    // if it's not yet time for the next frame... wait and sleep for a bit
    SDL_Delay(1);
    return;
  }

  next_frame += frame_length;    // otherwise, we're going to do at least 1 frame.  increment our time counter

  if (delta >= (frame_length * skip_frames_behind)) {    // if we have fallen too far behind.. we need to start skipping frames to catch up
    if (skipped_frames >= max_frame_skip) {            // if we have already skipped the maximum number of times.  "Give up" and just resync
      next_frame = SDL_GetTicks();
      skipped_frames = 0;
    } else {
      ++skipped_frames;    // otherwise, skip this frame
      fn(false);          // by "skip", I mean "run logic, but don't draw".
      return;
    }
  }