Fullscreen OpenGL with GLUT

fullscreen.c

#if defined(__APPLE__)
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#else
#include <GL/gl.h>
#include <GL/glu.h>
#endif
#include <GLUT/glut.h>

#include <stdio.h>

int is_fullscreen = 0;
int pos_x = 100;
int pos_y = 100;

void display(void) {
  glClearColor(1,1,1,0);
  glClear(GL_COLOR_BUFFER_BIT);

  glBegin(GL_TRIANGLES);
  {
    glColor3f(1,0,0);
    glVertex2f(0,0);

    glColor3f(0,1,0);
    glVertex2f(.5,0);

    glColor3f(0,0,1);
    glVertex2f(.5,.5);
  }
  glEnd();

  glutSwapBuffers();
}

void idle(void) {
  if (!is_fullscreen) {
    pos_x = glutGet(GLUT_WINDOW_X);
    pos_y = glutGet(GLUT_WINDOW_Y);
  }
}

void toggle_fullscreen() {
  if (is_fullscreen) {
    glutReshapeWindow(1000, 625);
    glutPositionWindow(pos_x, pos_y);
    printf("%d, %d\n", pos_x, pos_y);
  } else {
    glutFullScreen();
  }
  is_fullscreen = !is_fullscreen;
}

void reshape(int x, int y) {
  printf("Resizing to... %d, %d\n", x, y);
}

void keyboard(unsigned char key, int x, int y) {
  switch (key) {
    case 'f':
      toggle_fullscreen();
      break;
  }
}

int main(int argc, char *argv[]) {
  glutInit(&argc, argv);

  glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
  glutCreateWindow("My Game");
  glutReshapeWindow(900, 600);
  glutPositionWindow(pos_x, pos_y);
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutIdleFunc(idle);
  glutKeyboardFunc(keyboard);

  glutMainLoop();

  return 0;
}