opengl_glewglfw

Basic.shader

#shader vertex
#version 330 core

layout(location = 0) in vec4 position;

void main()
{
	gl_Position = position;
};

#shader fragment
#version 330 core

layout(location = 0) out vec4 color;

void main()
{
	color = vec4(0.3,0.4,0.8,1.0);
};

main.cpp

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <string>
#include <fstream>
#include <sstream>

struct ShaderProgramSource
{
	std::string VertexSource;
	std::string FragmentSource;
};

static ShaderProgramSource ParseShader(std::string filepath)
{
	std::ifstream stream(filepath);

	enum class ShaderType
	{
		NONE = -1, VERTEX = 0, FRAGMENT = 1
	};

	std::string line;
	std::stringstream ss[2];
	ShaderType type = ShaderType::NONE;

	auto _p = [](const std::string& l, const std::string& v) {return l.find(v) != std::string::npos; };

	while (getline(stream, line)) {
		if (_p(line, "#shader"))
		{
			if (_p(line, "vertex")) type = ShaderType::VERTEX;
			else if (_p(line, "fragment")) type = ShaderType::FRAGMENT;
		}
		else {
			ss[(int)type] << line << "\n";
		}
	}

	return { ss[0].str(),ss[1].str() };
}

static unsigned int CompileShader(unsigned int type, const std::string& source) {
	unsigned int id = glCreateShader(type);
	const char* src = source.c_str();
	//when pass pointer src you are passing a pointer to pointer
	//(an array of array), so you pass the pointer of the pointer to src
	glShaderSource(id, 1, &src, nullptr);
	glCompileShader(id);

	//TODO error handling
	int result;
	glGetShaderiv(id, GL_COMPILE_STATUS, &result);
	if (result == GL_FALSE)
	{
		int length;
		glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
		char* message = (char*)_malloca(length * sizeof(char));
		glGetShaderInfoLog(id, length, &length, message);
		std::cout << "Failed to compile " 
			<< (type == GL_VERTEX_SHADER ? "vertex" : "fragment") << "\n";
		std::cout << message << "\n";
	}


	return id;
}

static unsigned int CreateShader(const std::string& vertexShader, const std::string& fragmentShader)
{
	unsigned int program = glCreateProgram();
	unsigned int vShader = CompileShader(GL_VERTEX_SHADER, vertexShader);
	unsigned int fShader = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);

	glAttachShader(program, vShader);
	glAttachShader(program, fShader);

	glLinkProgram(program);
	glValidateProgram(program);

	glDeleteShader(vShader);
	glDeleteShader(fShader);

	return program;
}

int main(void)
{
	GLFWwindow* window;

	/* Initialize the library */
	if (!glfwInit())
		return -1;

	/* Create a windowed mode window and its OpenGL context */
	window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
	if (!window)
	{
		glfwTerminate();
		return -1;
	}

	/* Make the window's context current */
	glfwMakeContextCurrent(window);

	if (glewInit() != GLEW_OK) {
		std::cout << "ERROR\n";
	}
	std::cout << glGetString(GL_VERSION) << "\n";
	std::cout << "test\n";

	
	float positions[] = {
		-0.5f, -0.5f, // 0
		 0.5f, -0.5f, // 1
		 0.5f,	0.5f, // 2
		-0.5f,	0.5f  // 3
	};

	unsigned int indices[] = {
		0,1,2,
		2,3,0
	};

	unsigned int buffer;
	glGenBuffers(1, &buffer);
	//BIND == SELECT
	glBindBuffer(GL_ARRAY_BUFFER, buffer);
	glBufferData(GL_ARRAY_BUFFER, 6*2*sizeof(float), positions, GL_STATIC_DRAW);

	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2*sizeof(float), 0);

	unsigned int ibo;
	glGenBuffers(1, &ibo);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, 6*sizeof(unsigned int), indices, GL_STATIC_DRAW);

	//std::string vertexShader 
		
	//std::string fragmentShader

	ShaderProgramSource source = ParseShader("res/shaders/Basic.shader");

	std::cout << "Vertex:\n";
	std::cout << source.VertexSource << "\n";
	std::cout << "Fragment:\n";
	std::cout << source.FragmentSource << "\n";

	unsigned int shader = CreateShader(source.VertexSource, source.FragmentSource);
	glUseProgram(shader);

	/* Loop until the user closes the window */
	while (!glfwWindowShouldClose(window))
	{
		/* Render here */
		glClear(GL_COLOR_BUFFER_BIT);

	
		//glDrawArrays(GL_TRIANGLES, 0, 3);

		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr);
		/* Swap front and back buffers */
		glfwSwapBuffers(window);

		/* Poll for and process events */
		glfwPollEvents();
	}

	glDeleteProgram(shader);

	glfwTerminate();
	return 0;
}