static bool      KeyCallbacksInitialized=false;
static twKeyFunc twKeyCallbackArray[128];
static char*     twKeyCallbackDoc[128];

//keyboard settings
void twKeyCallback(char key, twKeyFunc fun, char* doc) {
    if( KeyCallbacksInitialized ) {
        twKeyCallbackArray[key] = fun;
        twKeyCallbackDoc[key] = doc;
    } else {
        printf("Keyboard Callbacks not yet initialized. Call this after twMainInit\n");
    }
}

void twHelp(unsigned char key, int x, int y) {
    int i;
    printf("This software is designed to help in learning and teaching\nabout using OpenGL to build 3D graphics programs.\nCopyright (C) 2006 Scott D. Anderson\nscott.anderson@acm.org\nThis is free software distributed under the GNU General Public License.\n");
    for(i=0;i<128;i++) 
        if( twKeyCallbackArray[i] != 0 ) {
            if(isgraph(i)) {
                printf("%3c: %s\n",i,twKeyCallbackDoc[i]);
            } else {
                switch(i) {
                case 32: printf("SPC: %s\n",twKeyCallbackDoc[i]); break;
                case 9:  printf("TAB: %s\n",twKeyCallbackDoc[i]); break;
                case 27: printf("ESC: %s\n",twKeyCallbackDoc[i]); break;
                default: printf("^%c : %s\n",i+64,twKeyCallbackDoc[i]); break;
                }
            }
        }
}

void twQuit(unsigned char key, int x, int y) {
  exit(0);
}

void twStopAndRefresh(unsigned char key, int x, int y) {
  glutIdleFunc(NULL);
  glutPostRedisplay();
}

void twPause(unsigned char key, int x, int y) {
  glutIdleFunc(NULL);
}

void twBoundingBoxToggle(unsigned char key, int x, int y) {
    Toggles[BB] = ! Toggles[BB];
   glutPostRedisplay();
}

void twLightingToggle(unsigned char key, int x, int y) {
    Toggles[LIGHTING] = ! Toggles[LIGHTING];
   glutPostRedisplay();
}

void twShadingToggle(unsigned char key, int x, int y) {
    Toggles[SMOOTH] = ! Toggles[SMOOTH];
   glutPostRedisplay();
}

void twReset (unsigned char key, int x, int y) {
   glutIdleFunc(NULL); 
   twZview();
   glutPostRedisplay();
}

// does a 10 degree rotation around y axis
void twRotViewY(unsigned char key, int x, int y) {
    twTriple yAxis={0,1,0};
    twRotateViewpoint(10,yAxis);
}

// does a 10 degree rotation around x axis
void twRotViewX(unsigned char key, int x, int y) {
    twTriple xAxis={1,0,0};
    twRotateViewpoint(10,xAxis);
}

// does a 10 degree pan (yaw) around y axis
void twPanView(unsigned char key, int x, int y) {
    twTriple yAxis={0,1,0};
    twRotateVPN(10,yAxis);
}

// Zoom in by the given number of degrees, relative to current
// FieldOfView.  If the field of view would drop to zero or less, it
// returns, leaving the field of view unchanged.  If the field of view
void twZoom(GLfloat degrees) {
    GLfloat newFOV = FieldOfView - degrees;
    if(newFOV <= 0) return;
    FieldOfView = newFOV;
    glutPostRedisplay();
}

void twZoom1() {
    twZoom(1);
}

void twStartZooming(unsigned char key, int x, int y) {
    glutIdleFunc(twZoom1);
}

void twNextFrame(unsigned char key, int x, int y) {
    twNextFrame();
}

void twKeyboardCallback (unsigned char key, int x, int y) {
  twKeyFunc fun;
  if (key>128) return;
  fun = twKeyCallbackArray[key];
  if (fun==0) {
      printf("No callback for %c (%d)\n",key,key);
      return;
  }
  fun(key,x,y);
}

void twSaveFrame(int width, int height, char *fname, bool verbose) {
    FILE *fp;
    register int y;
    unsigned char *pixels;
    int n;

    if( verbose ) printf("Saving image %s\n",fname);
    fp = fopen(fname,"w");
    if (!fp) {
        printf("Unable to open file '%s'\n",fname);
        return;
    }
    fprintf(fp, "P6");
    fprintf(fp, "%d %d ", width, height);
    fprintf(fp, "%d", 255);     /* max value */
    putc(13,fp);                /* carriage return character */
    pixels = (unsigned char*) malloc(3*width);

    for ( y = height-1; y >=0; y-- ) {
        glReadPixels(0,y,width,1,GL_RGB,GL_UNSIGNED_BYTE, (GLvoid *) pixels);
        for (n=0; n<3*width; n++) {
            putc(pixels[n],fp);
        }
        //    fwrite(pixels, 3, width, fp);
    }
    fclose(fp);
}

static int frameNumber = 1;

void twSave (unsigned char key, int x, int y) {
    char file[19];
    sprintf(file, "saved-frame%03d.ppm", frameNumber++);
    twSaveFrame(windowWidth, windowHeight, file, false);
    glutPostRedisplay();
} 

void twKeyInit() {
  int i;
  for(i=0;i<128;i++) twKeyCallbackArray[i] = 0;
  KeyCallbacksInitialized = true;
  twKeyCallback(27,  twQuit, "Quit");
  twKeyCallback(32,  twStopAndRefresh, "Stop animation, if any, and refresh");
  twKeyCallback('+', twSpinCommand, "double spin step");
  twKeyCallback('-', twSpinCommand, "halve spin step");
  twKeyCallback('b', twBoundingBoxToggle, "Toggle Bounding Box");
  twKeyCallback('l', twLightingToggle, "Toggle Lighting");
  twKeyCallback('s', twShadingToggle, "Toggle Smooth Shading");
  twKeyCallback('q', twQuit, "Quit");
  twKeyCallback('p', twPause, "Pause animation");
  twKeyCallback('r', twReset, "Reset to original screen");
  twKeyCallback('n', twNextFrame, "next frame of animation");
  twKeyCallback('x', twSpinCommand, "Spin around the x axis");
  twKeyCallback('y', twSpinCommand, "Spin around the y axis");
  twKeyCallback('z', twSpinCommand, "Spin around the z axis");
  twKeyCallback('X', twViewCommand, "View from positive X axis");
  twKeyCallback('Y', twViewCommand, "View from positive Y axis");
  twKeyCallback('Z', twViewCommand, "View from positive Z axis");
  //twKeyCallback('s', twRotViewY, "10 degrees around y");
  //twKeyCallback('t', twRotViewX, "10 degrees around x");
  //twKeyCallback('P', twPanView, "10 degrees pan around y");
  twKeyCallback('?', twHelp,"Help");
  twKeyCallback('i', twStartZooming, "start zooming in");
  twKeyCallback('S', twSave, "save frame");
}