02-first window

#include <iostream>  
#include <glad/glad.h>  
#include <GLFW/glfw3.h>  
  
void framebuffer_size_callback(GLFWwindow* window, int width, int height);//调整窗口大小时自适应调整渲染视口  
  
void processInput(GLFWwindow *window);  //检测ESC是否被按下，并关闭窗口  
  
  
int main()  
{  
  
  
    glfwInit();  //初始化GLFW  
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);  //主版本号  
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);  //次版本号  
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);  //使用core_profile模式  
    //glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);  //mac系统下需要开启  
 
   //  
   GLFWwindow* window = glfwCreateWindow(800, 600, "test", NULL, NULL);  //创建一个窗口对象  
   if (window == NULL)  
   {  
       std::cout << "Failed to create GLFW window" << std::endl;  
       glfwTerminate();  
       return -1;  
   }  
   glfwMakeContextCurrent(window);  //设置window为当前线程的主上下文  
 
 
   if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))  //GLAD初始化  
   {  
       std::cout << "Failed to initialize GLAD" << std::endl;  
       return -1;  
   }  
 
   glViewport(0, 0, 800, 600);  //设置渲染窗口的尺寸大小，即视口（Viewport）  
   glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);  //自适应调整渲染视口  
 
   //渲染循环  
   while(!glfwWindowShouldClose(window))  
   {  
       //输入  
        processInput(window);  
  
        //渲染指令 ...  
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);  //设置清空屏幕所用的颜色  
        glClear(GL_COLOR_BUFFER_BIT);  //清空屏幕的颜色缓冲  
  
  
        //检查并调用事件，交换缓冲  
        glfwSwapBuffers(window);  
        glfwPollEvents();  
    }  
  
    glfwTerminate();  //正确释放之前分配的资源  
    return 0;  
  
  
}  
  
  
  
void processInput(GLFWwindow *window)  
{  
    //一个窗口，和一个按键作为输入，该函数酱返回这个按键是否正在被按下，  
    if(glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)  
        glfwSetWindowShouldClose(window, true);  
}  
  
//调整用户窗口大小时更新视口的回调函数  
void framebuffer_size_callback(GLFWwindow* window, int width, int height)  
{  
    glViewport(0, 0, width, height);  
}