OpenGL learning record (1)

References:
https://learnopengl.com/
https://learnopengl-cn.github.io/

Simply open a window with OpenGL and fill it with color. The functions of each statement are basically annotated:

#define GLEW_STATIC
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>

//检查输入函数
void processInput(GLFWwindow* window)
{
    
    
	//按下ESC键时，将WindowShouldClose设为true，循环绘制将停止
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
	{
    
    
		glfwSetWindowShouldClose(window, true);
	}
}

//视口改变时的回调函数
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    
    
	glViewport(0, 0, width, height); //OpenGL渲染窗口的尺寸大小
}

int main() 
{
    
    
	glfwInit(); //初始化GLFW
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); //告诉GLFW要使用OpenGL的版本号
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); //主版本号、次版本号都为3，即3.3版本
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); //告诉GLFW使用核心模式(Core-profile)

	//打开 GLFW Window
	GLFWwindow* window = glfwCreateWindow(1920, 1080, "My OpenGL Game", nullptr, nullptr);
	if (window == nullptr) //若窗口创建失败，打印错误信息，终止GLFW并return -1
	{
    
    
		printf("Open window failed.");
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window); //创建OpenGL上下文
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback); //用户改变窗口大小的时候，视口调用回调函数

	//初始化GLEW
	glewExperimental = true;
	if (glewInit() != GLEW_OK) //若GLEW初始化失败，打印错误信息并终止GLFW窗口
	{
    
    
		printf("Init GLEW failed.");
		glfwTerminate();
		return -1;
	}

	//让程序在手动关闭之前不断绘制图像
	while (!glfwWindowShouldClose(window))
	{
    
    
		//检测输入
		processInput(window);

		//渲染指令
		glClearColor(0.f, 0.5f, 0.5f, 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区

		//检查并调用事件，交换缓冲区
		glfwSwapBuffers(window); //交换颜色缓冲区，前缓冲区保存最终输出的图像，后缓冲区负责绘制渲染指令，当渲染指令执行完毕后，交换前后缓冲区，使完整图像呈现出来，避免逐像素绘制图案时的割裂感
		glfwPollEvents(); //检查触发事件，如键盘输入、鼠标移动等
	}


	glfwTerminate(); //关闭GLFW并退出
	return 0;
}