前言

openGL使用GLFW、GLEW库绘制点，下面这段代码：绘制蓝色背景，中心点是一个黄色的点，由于代码比较简单，所以我把顶点着色器和片元着色器硬编码到c++程序中。问题就在这！！！由于着色器都写在字符串中，造成着色器的错误很难排查。

#include "glew/glew.h"
#include "glfw/glfw3.h"
#include <iostream>

using namespace std;

static const unsigned int scr_width = 800;
static const unsigned int scr_height = 600;

static const int numVAOs = 1;

GLuint renderingProgram;
GLuint vao[numVAOs];

static void error_callback(int error, const char* description)
{
	fprintf_s(stderr, "Error:%s\n", description);
}

static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
	if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
	{
		glfwSetWindowShouldClose(window, GLFW_TRUE);
	}
}

GLuint createShaderProgram()
{
	const char* vShaderSource =
		"#version core 430								\n"
		"void main(void)								\n"
		"{												\n"
		"	gl_Position = vec4(0.f, 0.f, 0.f, 1.f);     \n"
		"}												\n";

		const char* fShaderSource =
		"#version core 430								\n"
		"out vec4 fragColor;							\n"
		"void main(void)								\n"
		"{                                              \n"
		"	fragColor = vec4(1.0f, 1.0f, 0.0f, 1.0f);   \n"
		"}												\n";

		GLuint vShader = glCreateShader(GL_VERTEX_SHADER);
		GLuint fShader = glCreateShader(GL_FRAGMENT_SHADER);

		glShaderSource(vShader, 1, &vShaderSource, nullptr);
		glShaderSource(fShader, 1, &fShaderSource, nullptr);
		glCompileShader(vShader);
		glCompileShader(fShader);

		GLuint vfProgram = glCreateProgram();
		glAttachShader(vfProgram, vShader);
		glAttachShader(vfProgram, fShader);
		glLinkProgram(vfProgram);

		return vfProgram;
}

void init(GLFWwindow* window)
{
	
	renderingProgram = createShaderProgram();
	//缓冲区最后都会被存入顶点数组对象VAO(Vertex Array Object)
	glGenVertexArrays(numVAOs, vao);
	glBindVertexArray(vao[0]);
}

void display(GLFWwindow* window, double currentTime)
{
	glClearColor(0.f, 0.f, 1.f, 1.f);
	glClear(GL_COLOR_BUFFER_BIT);
	glUseProgram(renderingProgram);
	glPointSize(30.0f);
	glDrawArrays(GL_POINTS, 0, 1);
}


int main(int argc, char** argv)
{
	int glfwState = glfwInit();
	if (GLFW_FALSE == glfwState)
	{
		cout << "GLFW initialize failed. Invoke glfwInit()." << std::endl;
		glfwTerminate();
		exit(EXIT_FAILURE);
	}

	glfwSetErrorCallback(error_callback);

	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	GLFWwindow* window = glfwCreateWindow(scr_width, scr_height, "Draw point", nullptr, nullptr);
	if (nullptr == window)
	{
		cout << "GLFW create window failed! Invoke glfwCreateWindow()." << std::endl;
		//释放GLFW所有资源，直到调用glfwInit才能重新获取GLFW资源
		glfwTerminate();
		exit(EXIT_FAILURE);
	}

	//用于设置指定窗口的键回调，在按下、重复或释放键时调用该窗口
	glfwSetKeyCallback(window, key_callback);
	
	//调用线程上指定窗口的OpenGL或OpenGL ES上下文成为当前上下文。上下文一次只能在单个线程上成为当前上下文，并且每个线程一次只能有一个当前上下文。
	glfwMakeContextCurrent(window);
	
	int glewState = glewInit();
	if (GLEW_OK != glewState)
	{
		cout << "GLEW initialize failed! Invoke glfwInit()." << std::endl;
		exit(EXIT_FAILURE);
	}

	//由于这些原因，应用程序通常希望将交换间隔设置为1。可以将其设置为更高的值，但通常不建议这样做，因为这样会导致输入延迟。
	glfwSwapInterval(1);

	init(window);

	while (!glfwWindowShouldClose(window))
	{
		display(window, glfwGetTime());
		glfwSwapBuffers(window);
		glfwPollEvents();
	}

	//销毁窗口,以及撤销窗口事件
	glfwDestroyWindow(window);
	glfwTerminate();
	exit(EXIT_SUCCESS);
	return 0;
}