#include <string.h>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
 
#include <GLUT/glut.h>
#include <OpenGL/glext.h>

#define DTOR 0.0174532925
#define CROSSPROD(p1,p2,p3) \
   p3.x = p1.y*p2.z - p1.z*p2.y; \
   p3.y = p1.z*p2.x - p1.x*p2.z; \
   p3.z = p1.x*p2.y - p1.y*p2.x
   
#ifndef MIN
	#define MIN(a, b) ((a) < (b) ? (a) : (b))
#endif

int gMainWindow = 0;
int screenWidth = 600;
int screenHeight = 600;

int rColor = 1.0;
int gColor = 1.0;
int bColor = 1.0;

float angle = 0.0;
int spin = 0;

#pragma mark ---- GLUT callbacks ----

void init (void)
{	
	glClearColor(0.0, 0.0,0.0, 0.0);
}

void reshape (int w, int h)
{
	glViewport(0, 0, (GLuint) w,(GLuint) h);
	glutPostRedisplay();
//	glClearColor(((double) w/screenWidth) * 0.5,((double) w/screenWidth) * 0.5,((double) w/screenWidth) * 0.5, 1.0);
}

void maindisplay(void)
{
//	glClearColor(0.0, 0.0, 0.0, 0.0);
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(rColor, gColor, bColor);
	glLoadIdentity();
	glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
	glRotatef(angle, 0.0, 0.0, 1.0);
	glBegin(GL_POLYGON);
		glVertex2f(-0.5, -0.5);
		glVertex2f(-0.5, 0.5);
		glVertex2f(0.5, 0.5);
		glVertex2f(0.5, -0.5);
	glEnd();
//	glFinish();
	glutSwapBuffers();
}

void special(int key, int px, int py)
{
}

void mouse (int button, int state, int x, int y)
{
}

void key(unsigned char inkey, int px, int py)
{
	switch (inkey)
	{
		case 'r':
			if (rColor > 0.5)
				rColor = 0.0;
			else
				rColor = 1.0;
			break;
		case 's':
			if (spin == 0)
				spin = 1;
			else
				spin = 0;
			break;
		default:
			break;
	}
	glutPostRedisplay();
}

void timer(int temp)
{
	if (spin)
	{
		angle += 0.1;
		if (angle > 360.0)
			angle = angle - 360.0;
		glutPostRedisplay();	
	}
	glutTimerFunc(100, timer, 0);
}

#pragma mark ---- main ----

int main (int argc, const char * argv[])
{
    glutInit(&argc, (char **)argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); // non-stereo for main window
	glutInitWindowPosition (300, 50);
	glutInitWindowSize (screenWidth, screenHeight);
	gMainWindow = glutCreateWindow("GLUT Basics");

    init(); // standard GL init

    glutReshapeFunc (reshape);
    glutDisplayFunc (maindisplay);
	glutKeyboardFunc (key);
//	glutSpecialFunc (special);
//	glutMouseFunc (mouse);
//	glutIdleFunc(idle);
	glutTimerFunc(100, timer, 0);
    glutMainLoop();
    return 0;
}