test.cpp

/* Ask for an OpenGL Core Context */
#include <iostream>
#include "glad/glad.h"

#include <GLFW/glfw3.h>

#define BUFFER_OFFSET(i) ((char *)NULL + (i))

// Shaders
const GLchar* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 position;\n"
"void main()\n"
"{\n"
"gl_Position = vec4(position.x, position.y, position.z, 1.0);\n"
"}\0";
const GLchar* fragmentShaderSource = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\n\0";

void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);

int main(int argc, char** argv)
{
  GLFWwindow* window;

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

#ifdef __APPLE__
  /* We need to explicitly ask for a 3.2 context on OS X */
  glfwWindowHint (GLFW_CONTEXT_VERSION_MAJOR, 4);
  glfwWindowHint (GLFW_CONTEXT_VERSION_MINOR, 1);
  glfwWindowHint (GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // ONLY FOR MACOS
  glfwWindowHint (GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#endif

  /* Create a windowed mode window and its OpenGL context */
  window = glfwCreateWindow( 800,600, "Hello World", NULL, NULL );
  if (!window)
  {
     glfwTerminate();
     return -1;
  }

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

  // register callback functions
  glfwSetKeyCallback(window, key_callback);

    // Initialize GLAD to setup the OpenGL Function pointers
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize glad" << std::endl;
        return -1;
    }
  // define shader
    // Build and compile our shader program
    // Vertex shader
    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER); // MUST initilize glad first, or this function will crash!

    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    // Check for compile time errors
    GLint success;
    GLchar infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }
    // Fragment shader
    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);
    // Check for compile time errors
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }
    // Link shaders
    GLuint shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    // Check for linking errors
    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
    }
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

  // draw triangle
  GLfloat vertices[] = {
   -1.0f, -1.0f, 0.0f,
   1.0f, -1.0f, 0.0f,
   0.0f,  1.0f, 0.0f,
  };

    GLuint VBO, VAO;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    // Bind the Vertex Array Object first, then bind and set vertex buffer(s) and attribute pointer(s).
    glBindVertexArray(VAO);

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

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0); // Note that this is allowed, the call to glVertexAttribPointer registered VBO as the currently bound vertex buffer object so afterwards we can safely unbind

    glBindVertexArray(0); // Unbind VAO (it's always a good thing to unbind any buffer/array to prevent strange bugs)

  /* Loop until the user closes the window */
  while (!glfwWindowShouldClose(window))
  {
    /* Render here */
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear the buffers
    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);

    // draw triangle
    glUseProgram(shaderProgram);
    glBindVertexArray(VAO);
    glDrawArrays(GL_TRIANGLES, 0, 3);
    glBindVertexArray(0);

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

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

  // Properly de-allocate all resources once they've outlived their purpose
  glDeleteVertexArrays(1, &VAO);
  glDeleteBuffers(1, &VBO);

  glfwTerminate();
  return 0;
}

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