/*
 * animateSquare.cpp
 *
 *  Created on: Feb 15, 2013
 *      Author: debure
 */
#include <GL/glut.h>
#include <stdlib.h>

#define DTOR 3.14159/180.0  // convert degrees to radians
float theta;                // angle of rotation

void myinit(void) {

  glClearColor(0.0, 0.0, 0.0, 1.0);    // black background
  glColor3f(0.0, 0.0, 0.0);

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(-2.0, 2.0, -2.0, 2.0);  // sets up the viewing transform
  glMatrixMode(GL_MODELVIEW);

}

void display(void) {

  glEnableClientState(GL_VERTEX_ARRAY);   //  must have this set to use glDrawElements

  // square is created at the origin
  GLfloat sq_vertices[8][2] = {{-1.0,-1.0},{1.0,-1.0},{1.0, 1.0},{-1.0,1.0}};
  GLubyte sqIndices[4]={0,1,2,3};

  glVertexPointer(2, GL_FLOAT, 0, sq_vertices);   // tells where the array of vertices is located

  // code for rotating square
  glClear(GL_COLOR_BUFFER_BIT);
  glPushMatrix();
  glLoadIdentity();
  glRotatef(theta*DTOR, 0.0, 0.0, 1.0);
  glColor3f(0.0, 1.0, 1.0);
  glDrawElements(GL_QUADS, 4, GL_UNSIGNED_BYTE, sqIndices);   // replaces GL_BEGIN..GL_END sequence
  glPopMatrix();

  glutSwapBuffers();
  glFlush();
}

void idle(void){
  theta += 5;            // modify rotation angle in degrees that is used in display
  glutPostRedisplay();
}


int main(int argc, char** argv) {

  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB );  // double buffering needed for animation
  glutInitWindowSize(600, 600);
  glutInitWindowPosition(0,0);
  glutCreateWindow("Rotating Square");
  glutDisplayFunc(display);
  glutIdleFunc(idle);

  myinit();
  glutMainLoop();
  return 0;
}