open.gl tutorials #3 drawing GLFW code

// Link statically with GLEW
#define GLEW_STATIC

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

// Shader sources
const GLchar* vertexSource =
    "#version 150 core\n"
    "in vec2 position;"
    "in vec3 color;"
    "out vec3 Color;"
    "void main() {"
    "   Color = color;"
    "   gl_Position = vec4(position, 0.0, 1.0);"
    "}";
const GLchar* fragmentSource =
    "#version 150 core\n"
    "in vec3 Color;"
    "out vec4 outColor;"
    "void main() {"
    "   outColor = vec4(Color, 1.0);"
    "}";

int main(int argc, char* argv[])
{
    glfwInit();
    GLFWwindow* window = glfwCreateWindow(640, 480, "OpenGL", NULL, NULL);
    glfwMakeContextCurrent(window);

    // Initialize GLEW
    glewExperimental = GL_TRUE;
    glewInit();

    // Create Vertex Array Object
    GLuint vao;
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);

    // Create a Vertex Buffer Object and copy the vertex data to it
    GLuint vbo;
    glGenBuffers(1, &vbo);

    GLfloat vertices[] = {
        -0.5f,  0.5f, 1.0f, 0.0f, 0.0f, // Top-left
         0.5f,  0.5f, 0.0f, 1.0f, 0.0f, // Top-right
         0.5f, -0.5f, 0.0f, 0.0f, 1.0f, // Bottom-right
        -0.5f, -0.5f, 1.0f, 1.0f, 1.0f  // Bottom-left
    };

    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    // Create an element array
    GLuint ebo;
    glGenBuffers(1, &ebo);

    GLuint elements[] = {
        0, 1, 2,
        2, 3, 0
    };

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);

    // Create and compile the vertex shader
    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexSource, NULL);
    glCompileShader(vertexShader);

    // Create and compile the fragment shader
    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
    glCompileShader(fragmentShader);

    // Link the vertex and fragment shader into a shader program
    GLuint shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glBindFragDataLocation(shaderProgram, 0, "outColor");
    glLinkProgram(shaderProgram);
    glUseProgram(shaderProgram);

    // Specify the layout of the vertex data
    GLint posAttrib = glGetAttribLocation(shaderProgram, "position");
    glEnableVertexAttribArray(posAttrib);
    glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), 0);

    GLint colAttrib = glGetAttribLocation(shaderProgram, "color");
    glEnableVertexAttribArray(colAttrib);
    glVertexAttribPointer(colAttrib, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(2 * sizeof(GLfloat)));

    while(!glfwWindowShouldClose(window))
    {
        if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
            glfwSetWindowShouldClose(window, GL_TRUE);

        glfwSwapBuffers(window);
        glfwPollEvents();


        // Clear the screen to black
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        // Draw a rectangle from the 2 triangles using 6 indices
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

        // Swap buffers

}
    glDeleteProgram(shaderProgram);
    glDeleteShader(fragmentShader);
    glDeleteShader(vertexShader);

    glDeleteBuffers(1, &ebo);
    glDeleteBuffers(1, &vbo);

    glDeleteVertexArrays(1, &vao);
}