print fps sfml
void print_fps(){
static sf::Clock clock; // google "static with variables", if you need
static sf::Time last_time = clock.getElapsedTime();
sf::Time current_time = clock.getElapsedTime();
float fps = 1.f / (current_time.asSeconds() - last_time.asSeconds());
last_time = current_time;
printf("FPS: %f\n", fps);
}
// put this function somewhere in main cycle