Um código simples pra testar o framerate no SDL

teste_fps.cpp

#include "SDL2/SDL.h"
#include <stdio.h>

// How many frames time values to keep
// The higher the value the smoother the result is...
// Don't make it 0 or less :)
#define FRAME_VALUES 10

// An array to store frame times:
Uint32 frametimes[FRAME_VALUES];

// Last calculated SDL_GetTicks
Uint32 frametimelast;

// total frames rendered
Uint32 framecount;

// the value you want
float framespersecond;

// This function gets called once on startup.
void fpsinit() {
	// Set all frame times to 0ms.
	for (int i = 0; i < FRAME_VALUES; i++)
		frametimes[i] = 0;
	framecount = 0;
	framespersecond = 0;
	frametimelast = SDL_GetTicks();
}

void fpsthink() {
	Uint32 frametimesindex;
	Uint32 getticks;
	Uint32 count;
	Uint32 i;

	// frametimesindex is the position in the array. It ranges from 0 to FRAME_VALUES.
	// This value rotates back to 0 after it hits FRAME_VALUES.
	frametimesindex = framecount % FRAME_VALUES;

	// store the current time
	getticks = SDL_GetTicks();

	// save the frame time value
	frametimes[frametimesindex] = getticks - frametimelast;

	// save the last frame time for the next fpsthink
	frametimelast = getticks;

	// increment the frame count
	framecount++;

	// Work out the current framerate

	// The code below could be moved into another function if you don't need the value every frame.

	// I've included a test to see if the whole array has been written to or not. This will stop
	// strange values on the first few (FRAME_VALUES) frames.
	if (framecount < FRAME_VALUES) {
		count = framecount;
	} else {
		count = FRAME_VALUES;
	}

	// add up all the values and divide to get the average frame time.
	framespersecond = 0;
	for (i = 0; i < count; i++) {
		framespersecond += frametimes[i];
	}
	framespersecond /= count;

	// now to make it an actual frames per second value...
	framespersecond = 1000.f / framespersecond;
}

int main(int argc, char** argv) {
	SDL_Init(0);

	// put this as close as possible to the start of the loop (before it starts!)
	fpsinit();

	while (1) {
		// render stuff here
		// draw();
		SDL_Delay(500); // 500 should make 2 frames per second.

		fpsthink();
		printf("%f\n", framespersecond);
	}

	SDL_Quit();

	return 0;
}