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

int singleb, doubleb;

void myinit();
void displays();
void displayd();
void spinDisplay();
void mouse(int btn, int state, int x, int y);
void myReshape(int w, int h);
void mykey(unsigned char key, int x, int y);
void quit_menu(int id);

int main(int argc, char *argv[])
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	singleb = glutCreateWindow("single buffered");
	myinit();
	glutDisplayFunc(displays);
	glutReshapeFunc(myReshape);
	glutIdleFunc(spinDisplay);
	glutMouseFunc(mouse);
	glutKeyboardFunc(mykey);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
	glutInitWindowPosition(310, 0);
	doubleb = glutCreateWindow("double buffered");
	myinit();
	glutDisplayFunc(displayd);
	glutReshapeFunc(myReshape);
	glutIdleFunc(spinDisplay);
	glutMouseFunc(mouse);
	glutKeyboardFunc(mykey);
	glutCreateMenu(quit_menu);
	glutAddMenuEntry("quit", 1);
	glutAttachMenu(GLUT_RIGHT_BUTTON);
	glutMainLoop();
}

void myinit()
{
	glClearColor(0.0, 0.0, 0.0, 0.0);
	glColor3f(1.0, 1.0, 1.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(-2.0, 2.0, -2.0, 2.0);
}

#define DEG_TO_RAD 0.017453
GLfloat theta = 0.0;

void displays()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glBegin(GL_POLYGON);
	glVertex2f(cos(DEG_TO_RAD * theta), sin(DEG_TO_RAD * theta));
	glVertex2f(-sin(DEG_TO_RAD * theta), cos(DEG_TO_RAD * theta));
	glVertex2f(-cos(DEG_TO_RAD * theta), -sin(DEG_TO_RAD * theta));
	glVertex2f(sin(DEG_TO_RAD * theta), -cos(DEG_TO_RAD * theta));
	glEnd();
	glFlush();
}

void displayd()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glBegin(GL_POLYGON);
	glVertex2f(cos(DEG_TO_RAD * theta), sin(DEG_TO_RAD * theta));
	glVertex2f(-sin(DEG_TO_RAD * theta), cos(DEG_TO_RAD * theta));
	glVertex2f(-cos(DEG_TO_RAD * theta), -sin(DEG_TO_RAD * theta));
	glVertex2f(sin(DEG_TO_RAD * theta), -cos(DEG_TO_RAD * theta));
	glEnd();
	glutSwapBuffers();
}

void spinDisplay()
{
	theta += 2.0;
	if (theta >= 360.0) theta -= 360.0;
	glutSetWindow(singleb);
	glutPostWindowRedisplay(singleb);
	glutSetWindow(doubleb);
	glutPostWindowRedisplay(doubleb);
}

void myReshape(int w, int h)
{
	glViewport(0, 0, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(-2.0, 2.0, -2.0, 2.0);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

void mouse(int btn, int state, int x, int y)
{
	if (btn == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
		glutIdleFunc(spinDisplay);
	if (btn == GLUT_MIDDLE_BUTTON && state == GLUT_DOWN)
		glutIdleFunc(NULL);
}

void mykey(unsigned char key, int x, int y)
{
	if (key == 'q' || key == 'Q') exit(0);
}

void quit_menu(int id)
{
	if (id == 1) exit(0);
}