main.cpp

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
using namespace std;

static unsigned int CompileShader(unsigned int type, const string& source){
    unsigned int id = glCreateShader(type);
    const char* src = source.c_str();
    glShaderSource(id, 1, &src, nullptr);
    glCompileShader(id);

    int result;
    glGetShaderiv(id, GL_COMPILE_STATUS, &result);
    if (result == GL_FALSE) {
        int length;
        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
        char* message = (char*) alloca(length * sizeof(char));
        glGetShaderInfoLog(id, length, &length, message);
        cout << "Failed to compile" << (type == GL_VERTEX_SHADER ? " vertex" : " fragment") << " shader!" << endl;
        cout << message << endl;
        glDeleteShader(id);
        return 0;
    }
    return id;
}

static unsigned int CreateShader(const string& vertexShader, const string& fragmentShader) {
    unsigned int program = glCreateProgram();
    unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
    unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);

    glAttachShader(program, vs);
    glAttachShader(program, fs);
    glLinkProgram(program);
    glValidateProgram(program);

    glDeleteShader(vs);
    glDeleteShader(fs);

    return program;
}

int main() {
    GLFWwindow* window;
    if (!glfwInit()) return -1;

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    window = glfwCreateWindow(640, 480, "Srinjoy", NULL, NULL);
    if (!window) {
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    if (glewInit() != GLEW_OK) {
        cout << "Error initialising glew" << endl;
        return -1;
    }

    cout << glGetString(GL_VERSION) << endl;

    float position[6] = {
        -0.5F, -0.5F,
         0.0F,  0.5F,
         0.5F, -0.5F
    };

    unsigned int buffer;
    glGenBuffers(1, &buffer);
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(float), position, GL_STATIC_DRAW);

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

    string vertexShader =
        "#version 330 core\n"
        "layout(location = 0) in vec4 position;\n"
        "void main() {\n"
        "   gl_Position = position;\n"
        "}";
    string fragmentShader =
        "#version 330 core\n"
        "layout(location = 0) out vec4 color;\n"
        "void main() {\n"
        "   color = vec4(1.0, 1.0, 0.0, 1.0);\n"
        "}";

    unsigned int shader = CreateShader(vertexShader, fragmentShader);
    glUseProgram(shader);


    while (!glfwWindowShouldClose(window)){
        glClear(GL_COLOR_BUFFER_BIT);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    glfwTerminate();
    return 0;
}