问题 在SDL中实现恒定的帧速率

我正在尝试制作一个以恒定帧速率运行的SDL程序。然而，我发现即使我的程序滞后很多并且跳过很多帧（即使它在低帧运行并且渲染不多）。

你们有什么建议让我的程序运行得更顺畅吗？

#include "SDL.h"
#include "SDL/SDL_ttf.h"

//in milliseconds
const int FPS = 24;
const int SCREENW = 400;
const int SCREENH = 300;
const int BPP = 32;

void apply_surface(int x, int y, SDL_Surface* source, SDL_Surface* destination) {

    SDL_Rect offset;

    offset.x = x;

    offset.y = y;



    if(SDL_BlitSurface(source, NULL, destination, &offset) < 0) {
        printf("%s\n", SDL_GetError());
    }

}

int main(int argc, char* argv[]) {
    //calculate the period
    double period = 1.0 / (double)FPS;
    period = period * 1000;
    int milliPeriod = (int)period;
    int sleep;

    SDL_Init(SDL_INIT_EVERYTHING);
    TTF_Init();

    TTF_Font* font = TTF_OpenFont("/usr/share/fonts/truetype/freefont/FreeMono.ttf", 24);
    SDL_Color textColor = { 0x00, 0x00, 0x00 };

    SDL_Surface* screen = SDL_SetVideoMode(SCREENW, SCREENH, BPP, SDL_SWSURFACE);
    SDL_Surface* message = NULL;

    Uint32 white = SDL_MapRGB(screen->format, 0xFF, 0xFF, 0xFF);

    SDL_Event event;

    char str[15];

    Uint32 lastTick;
    Uint32 currentTick;
    while(1) {
        while(SDL_PollEvent(&event)) {
            if(event.type == SDL_QUIT) {
                return 0;
            }
            else {
                lastTick = SDL_GetTicks();

                sprintf(str, "%d", lastTick);
                message = TTF_RenderText_Solid(font, str, textColor);
                if(message == NULL) { printf("%s\n", SDL_GetError()); return 1; }

                //the actual blitting
                SDL_FillRect(screen, &screen->clip_rect, white);
                apply_surface(SCREENW / 2, SCREENH / 2, message, screen);

                currentTick = SDL_GetTicks();

                //wait the appropriate amount of time
                sleep = milliPeriod - (currentTick - lastTick);
                if(sleep < 0) { sleep = 0; }
                SDL_Delay(sleep);

                SDL_Flip(screen);
            }
        }
    }

    TTF_CloseFont(font);
    TTF_Quit();
    SDL_Quit();

    return 0;
}