[笔记]音视频学习之SDL篇《二》 绘制平铺的背景图并居中放置另一图片

//Start up SDL and make sure it went ok
  if (SDL_Init(SDL_INIT_VIDEO) != 0) {
    logSDLError(std::cout, "SDL_Init");
    return 1;
  }
  //Setup our window and renderer
  SDL_Window *window = SDL_CreateWindow("Lesson 2", 100, 100, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
  if (window == nullptr) {
    logSDLError(std::cout, "CreateWindow");
    SDL_Quit();
    return 1;
  }
  SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
  if (renderer == nullptr) {
    logSDLError(std::cout, "CreateRenderer");
    cleanup(window);
    SDL_Quit();
    return 1;
  }

//The textures we'll be using
  const std::string resPath = getResourcePath("02sdl_learn");
  SDL_Texture *background = loadTexture(resPath + "background.bmp", renderer);
  SDL_Texture *image = loadTexture(resPath + "image.bmp", renderer);
  //Make sure they both loaded ok
  if (background == nullptr || image == nullptr) {
    cleanup(background, image, renderer, window);
    SDL_Quit();
    return 1;
  }

renderTexture(background, renderer, 0, 0);
renderTexture(background, renderer, bW, 0);
renderTexture(background, renderer, 0, bH);
renderTexture(background, renderer, bW, bH);

A sleepy rendering loop, wait for 3 seconds and render and present the screen each time
  //for (int i = 0; i < 3; ++i) {
    //Clear the window
    SDL_RenderClear(renderer);
    //Get the width and height from the texture so we know how much to move x,y by
    //to tile it correctly
    int bW, bH;
    SDL_QueryTexture(background, NULL, NULL, &bW, &bH);
    //We want to tile our background so draw it 4 times
    renderTexture(background, renderer, 0, 0);
    renderTexture(background, renderer, bW, 0);
    renderTexture(background, renderer, 0, bH);
    renderTexture(background, renderer, bW, bH);
    //Draw our image in the center of the window
    //We need the foreground image's width to properly compute the position
    //of it's top left corner so that the image will be centered
    int iW, iH;
    SDL_QueryTexture(image, NULL, NULL, &iW, &iH);
    int x = SCREEN_WIDTH / 2 - iW / 2;
    int y = SCREEN_HEIGHT / 2 - iH / 2;
    renderTexture(image, renderer, x, y);
    //Update the screen
    SDL_RenderPresent(renderer);
    //Take a quick break after all that hard work
    SDL_Delay(10000);
  /*}*/

cleanup(background, image, renderer, window);
SDL_Quit();