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

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

// Make the window context current
glfwMakeContextCurrent(window);

if(glewInit() != GLEW_OK) {
    cout << "Error!" << endl;
}

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

    glBegin(GL_TRIANGLES);
    glVertex2f(-0.5f, -0.5f);
    glVertex2f(0.0f, 0.5f);
    glVertex2f(0.5f, -0.5f);
    glEnd();

    // Swap front and back buffers
    glfwSwapBuffers(window);

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

glfwTerminate();
return 0; } */

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

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

// Make the window context current
glfwMakeContextCurrent(window);

if(glewInit() != GLEW_OK) {
    cout << "Error!" << endl;
}

// Define ours buffer
// Generate a buffer and return back his ID, to OpenGL identify that buffer and used.
unsigned int buffer;
glGenBuffers(1, &buffer);

// Select that buffer, first param, porpuse of using and second param buffer
glBindBuffer(GL_ARRAY_BUFFER, buffer);

// Define the data of the buffer, first params, type of that data, second param how big
float positions[6] = {
    -0.5f, -0.5f,
     0.0f,  0.5f,
     0.5f, -0.5f
};

glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(float), positions, GL_STATIC_DRAW);


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

    // We need shader to display triangle, otherwise, will display none.
    glDrawArrays(GL_TRIANGLES, 0, 3);

    // Swap front and back buffers
    glfwSwapBuffers(window);

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

glfwTerminate();
return 0; } */

if(!glfwInit()) {
    return -1;
}

window = glfwCreateWindow(640, 480, "Moderns OpenGL", NULL, NULL);
if(!window) {
    // GLFW window creation failed!
    glfwTerminate();
    return -1;
}

glfwMakeContextCurrent(window);

if(glewInit() != GLEW_OK) {
    cout << "Error!" << endl;
}

float positions[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), positions, GL_STATIC_DRAW);

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

while(!glfwWindowShouldClose(window)) {
    
    glClear(GL_COLOR_BUFFER_BIT);

    glDrawArrays(GL_TRIANGLES, 0, 3);

    glfwSwapBuffers(window);

    glfwPollEvents();
}

glfwTerminate();
return 0; } */ //-- Adding shaders // vertex and fragment shader type are 90% more used shader on graphics. // vertex shader, pourpose is to tell gpu where position on the screen we want to render specific each vertex. If we have three vertex, we call this 3 time. // fragment or pixel shader, determine where to fill pixel inside of the figure we create and color. #include <iostream> #include <GL/glew.h> #include <GLFW/glfw3.h>

// 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*) 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; }

// Shader objects or files
unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);

// Attach to the program
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glValidateProgram(program);

glDeleteShader(vs);
glDeleteShader(fs);

return program; }

if(!glfwInit()) {
    return -1;
}

window = glfwCreateWindow(640, 480, "Moderns OpenGL", NULL, NULL);
if(!window) {
    // GLFW window creation failed!
    glfwTerminate();
    return -1;
}

glfwMakeContextCurrent(window);

if(glewInit() != GLEW_OK) {
    cout << "Error!" << endl;
}

float positions[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), positions, GL_STATIC_DRAW);

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

// Writing shader
string vertexShader = 
    // Version of GLSL
    "#version 330 core \n"
    "\n"
    "layout(location = 0) in vec4 position;"
    "\n"
    "void main()\n"
    "{\n"
    "gl_Position = position; \n"
    "} \n";

string fragmentShader = 
    // Version of GLSL
    "#version 330 core \n"
    "\n"
    "layout(location = 0) out vec4 color;"
    "\n"
    "void main()\n"
    "{\n"
    "color = vec4(1.0, 0.0, 0.0, 1.0); \n"
    "} \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; }