#include <stdexcept>

 #include <string>

 #include <iostream>

 #include "SDL.h"

 #include "SDL_image.h"

 //屏幕宽度

 const int SCREEN_WIDTH = ;

 const int SCREEN_HEIGHT = ;

 //全局窗口和渲染器

 SDL_Window *window = nullptr;

 SDL_Renderer *renderer = nullptr;

 //加载图片

 SDL_Texture* LoadImage(std::string file)

 {

     SDL_Texture* tex = nullptr;

     tex = IMG_LoadTexture(renderer, file.c_str());

     if (tex == nullptr)

         throw std::runtime_error("Failed to load image: " + file + IMG_GetError());

     return tex;

 }

 //将表面应用到渲染器

 void ApplySurface(int x, int y, SDL_Texture *tex, SDL_Renderer *rend)

 {

     SDL_Rect pos;

     pos.x = x;

     pos.y = y;

     SDL_QueryTexture(tex, NULL, NULL, &pos.w, &pos.h);

     SDL_RenderCopy(rend, tex, NULL, &pos);

 }

 int main(int argc, char** argv)

 {

     //初始化SDL

     if (SDL_Init(SDL_INIT_EVERYTHING) == -)

     {

         std::cout << SDL_GetError() << std::endl;

         return ;

     }

     //创建窗口

     window = SDL_CreateWindow("Lesson 4 - Event Driven Programming",

         SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,

         SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);

     if (window == nullptr)

     {

         std::cout << SDL_GetError() << std::endl;

         return ;

     }

     //创建渲染器

     renderer = SDL_CreateRenderer(window, -,

         SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);

     if (renderer == nullptr)

     {

         std::cout << SDL_GetError() << std::endl;

         return ;

     }

     //创建背景和前景纹理

     SDL_Texture *background = nullptr, *image = nullptr;

     try {

         background = LoadImage("background.png");

         image = LoadImage("event.png");

     }

     catch (const std::runtime_error &e) {

         std::cout << e.what() << std::endl;

         return ;

     }

     bool quit = false;

     SDL_Event e;

     //主循环（CPU高占用）

     while (!quit)

     {

         //轮询事件栈e

         while (SDL_PollEvent(&e))

         {

             //用户关闭窗口

             if (e.type == SDL_QUIT) quit = true;

             //用户按下键盘

             if (e.type == SDL_KEYDOWN) quit = true;

             //用户点击鼠标

             if (e.type == SDL_MOUSEBUTTONDOWN) quit = true;

             //清空渲染器

             SDL_RenderClear(renderer);

             //在渲染器内平铺背景

             int bW, bH;

             SDL_QueryTexture(background, NULL, NULL, &bW, &bH);

             for (int y = ; y <= SCREEN_HEIGHT; y += bH)

                 for (int x = ; x <= SCREEN_WIDTH; x += bW)

                     ApplySurface(x, y, background, renderer);

             //在渲染器中央放置前景

             int iW, iH;

             SDL_QueryTexture(image, NULL, NULL, &iW, &iH);

             int x = SCREEN_WIDTH /  - iW / ;

             int y = SCREEN_HEIGHT /  - iH / ;

             ApplySurface(x, y, image, renderer);

             //呈现渲染器

             SDL_RenderPresent(renderer);

         }

     }

     //释放资源

     SDL_DestroyTexture(background);

     SDL_DestroyTexture(image);

     SDL_DestroyRenderer(renderer);

     SDL_DestroyWindow(window);

     SDL_Quit();

     return ;

 }