/* Demo of the classic barn object.  This has a special callback to rotate
   it negatively around the y axis at 24 frames per second.

Implemented Fall 2006
Scott D. Anderson
*/

#include <stdio.h>
#include <tw.h>

GLfloat BarnAngle = 0.0;        // for rotating the barn

void display(void) {
    twDisplayInit();
    twCamera();

    GLfloat lightpos[] = { 3, 2, 1, 0 }; // directional light from low right side
    twGrayLight(GL_LIGHT0,lightpos,1,1,1);
    glEnable(GL_LIGHT0);
    glEnable(GL_LIGHTING);

    glPushMatrix();
    const float d = 255.0;
    twTriple roof = { 188/d, 143/d, 143/d }; // rosy brown 
    twTriple wall = { 178/d,  34/d,  34/d }; // firebrick
    glRotatef(BarnAngle,0,1,0);
    glScalef(10,10,10);
    twSolidBarn(wall,wall,roof);
    glPopMatrix();

    glFlush();
    glutSwapBuffers();
}

// True when timer animation on.  Also necessary so that the animation can turn itself off.
bool TimerAnimationOn = false;

// milliseconds per frame to yield 24 frames per second.  Alas, the
// integer value is 42 and it should be 41.67, so it's off by a little
const unsigned int MsecsPerFrame = 42;

// This function rotate the barn, redraw the screen, and sets up another
// timer interrupt, so that it's an infinite loop until the animation is
// stopped by a keyboard callback.

void rotateBarnAnimation(int cookie) {
    // printf("rotating barn to %f\n",BarnAngle);
    BarnAngle += 5;
    glutPostRedisplay();
    if(TimerAnimationOn) 
        glutTimerFunc(MsecsPerFrame, rotateBarnAnimation, 0);
}

void setTimer(unsigned char key, int x, int y) {
    TimerAnimationOn = !TimerAnimationOn;
    if( TimerAnimationOn ) {
        printf("starting timer animation\n");
        // Registers rotateBarnAnimation to be called in at least this
        // many milliseconds.  Last arg is a kind of cookie or identifer,
        // passed to the callback. In this case, we don't care, so we'll
        // just pass zero.  
        glutTimerFunc(MsecsPerFrame,
                      rotateBarnAnimation,
                      0);
    } else {
        printf("stopping timer animation\n");
    }
}

int main(int argc, char** argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  twInitWindowSize(500,500);
  glutCreateWindow(argv[0]);
  glutDisplayFunc(display);
  twBoundingBox(-10,10,0,10,-10,10);
  twMainInit();            
  twKeyCallback('t',setTimer,"starts/stops timer interrupt animation");
  glutMainLoop();
  return 0;
}