OpenGL basics with GLFW library

glfw_basics.c

#define GLEW_STATIC
#include <GL/glew.h>

#include <GLFW/glfw3.h>

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <limits.h>
#include <math.h>

#define BUF_SIZE 512


float vertices[] = {
  0.0f,  0.5f, 0.0f, 0.0f, 1.0f,
  0.5f, -0.5f, 0.0f, 1.0f, 0.0f,
  -0.5f, -0.5f, 1.0f, 0.0f, 0.0f,
};


const char * vertexSource = "#version 130\n"
  "in vec2 position;\n"
  "in vec3 color;\n"
  "out vec3 Color;\n"
  "void main()\n"
  "{\n"
  " Color = color;\n"
  " gl_Position = vec4(position, 0.0, 1.0);\n"
  "}\n";

const char * fragmentSource = "#version 130\n"
  "in vec3 Color;\n"
  "out vec4 outColor;\n"
  "void main()\n"
  "{\n"
  " outColor = vec4(Color, 1.0);\n"
  "}\n";

void error_callback(int num, const char * desc){
  fprintf(stderr, "Error:[%d]\t%s", num, desc);
}

void init(){
  if(!glfwInit()){
    fprintf(stderr, "Cannot Initialize GLFW\n");
    exit(EXIT_FAILURE);
  }
  glfwSetErrorCallback(error_callback);

  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
  glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
  glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
  
}

void finl(){
  glfwTerminate();
}

int main(){
  init();
  GLFWwindow * win = glfwCreateWindow(640, 480, "GLFW Basics", NULL, NULL);
  if(!win){
    fprintf(stderr, "Cannot create window");
    return -1;
  }
  glfwMakeContextCurrent(win);
  glewExperimental = GL_TRUE;
  glewInit();

  GLuint vertexBuffer;
  glGenBuffers(1, &vertexBuffer);

  GLuint vbo;
  glGenBuffers(1, &vbo);
  glBindBuffer(GL_ARRAY_BUFFER, vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

  GLuint vao;
  glGenVertexArrays(1, &vao);
  glBindVertexArray(vao);
  
  GLint status;
  char buffer[BUF_SIZE];
  
  GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
  glShaderSource(vertexShader, 1, &vertexSource, NULL);
  glCompileShader(vertexShader);
  glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &status);
  if(status != GL_TRUE){
    glGetShaderInfoLog(vertexShader, BUF_SIZE, NULL, buffer);
    fprintf(stderr, "Error compiling vertex shader: %s\n", buffer);
    return -1;
  }

  GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
  glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
  glCompileShader(fragmentShader);
  glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &status);
  if(status != GL_TRUE){
    glGetShaderInfoLog(fragmentShader, BUF_SIZE, NULL, buffer);
    fprintf(stderr, "Error compiling fragment shader: %s\n", buffer);
    return -1;
  }
  GLuint shaderProgram = glCreateProgram();
  glAttachShader(shaderProgram, vertexShader);
  glAttachShader(shaderProgram, fragmentShader);
  glBindFragDataLocation(shaderProgram, 0, "outColor");
  glLinkProgram(shaderProgram);
  glUseProgram(shaderProgram);

  GLint posAttrib = glGetAttribLocation(shaderProgram, "position");
  glVertexAttribPointer(posAttrib, 2, GL_FLOAT,  GL_FALSE,
			5*sizeof(float), 0);
  glEnableVertexAttribArray(posAttrib);

  GLint colorAttrib = glGetAttribLocation(shaderProgram, "color");
  glVertexAttribPointer(colorAttrib, 3, GL_FLOAT, GL_FALSE,
			5*sizeof(float), (void*)(2*sizeof(float)));
  glEnableVertexAttribArray(colorAttrib);
  /* Uniforms */
  /* GLint uniColor = glGetUniformLocation(shaderProgram, "triangleColor"); */
  /* glUniform3f(uniColor, 1.0f, 0.0f, 0.0f); */

  /* /\* Time variables *\/ */
  /* struct timeval tnow, tstart; */
  /* gettimeofday(&tstart, NULL); */
  while(!glfwWindowShouldClose(win)){
    /* gettimeofday(&tnow, NULL); */
    /* long int secs = tnow.tv_sec - tstart.tv_sec; */
    /* long int usecs = tnow.tv_usec - tstart.tv_sec; */
    /* glUniform3f(uniColor, (sin(secs+1e-6*usecs) + 1.0f)/2.0f, 0.0f, 0.0f); */

    /* glClearColor(0.0f, 0.0f, 0.0f, 1.0f); */
    /* glClear(GL_COLOR_BUFFER_BIT); */
    
    glDrawArrays(GL_TRIANGLES, 0, 3);
    glfwSwapBuffers(win);
    glfwPollEvents();
  }
  
  glfwDestroyWindow(win);
  finl();
  return 0;
}

/* Local Variables: */
/* compile-command: "gcc -o glfw_basics glfw_basics.c -lglfw `pkg-config --cflags --libs glew` -lm" */
/* End: */