// Computer Graphics - Amir Hesami
// This programs shows the effect of using glutIdelFunc()
// rotatingrectangle1.cpp


#include <GL/glut.h>
#include <math.h>

#pragma comment(lib, "opengl32.lib")  // Link OpenGL32.lib
#pragma comment(lib, "glu32.lib")	  // Link Glu32.lib
#pragma comment(lib, "glut32.lib")    // Link Glut32.lib
#pragma comment(linker, "/entry:\"mainCRTStartup\"" )  // set the entry point to be main()
#pragma comment(linker, "/subsystem:\"Windows\"" )  // set the entry point to be main()


#define DEG_TO_RAD 57.29578 //degree to radian
void display();
void idle();

void init();

GLfloat theta = 0.0;

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE| GLUT_RGB);
	glutInitWindowSize(500,500);
	glutInitWindowPosition(100,100);
	glutCreateWindow("Rotating Rectangle 1");
	glutDisplayFunc(display);
	glutIdleFunc(idle);
	
	init();
	glutMainLoop();
	return 0;
}

void display()
{
	//Clear the window
	glClear(GL_COLOR_BUFFER_BIT);

	//Set the drawing color to red
	glColor3f(1.0,0.0,0.0);
    GLfloat theta1 = theta * DEG_TO_RAD;
	
	//draw unit square polygon
	glBegin(GL_POLYGON);
	   glVertex2f(cos(theta1),sin(theta1));
	   glVertex2f(-sin(theta1),cos(theta1));
	   glVertex2f(-cos(theta1),-sin(theta1));
	   glVertex2f(sin(theta1),-cos(theta1));
    glEnd();
    
	//Flush the buffer
	glFlush();
}

void init()
{
	//Set the background color
	glClearColor(1.0,1.0,1.0,1.0);
    
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(-2.0,2.0,-2.0,2.0);
}

void idle()
{
	theta +=2.0;
	if(theta >360.0) theta -=360;
	glutPostRedisplay();
	
}