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

GLsizei wh = 500, ww = 500; 
GLfloat size = 10.0; 
void drawSquare(int x, int y)
{
y = wh - y;
glColor3ub( (char) rand()%256, (char) rand()%256,
(char) rand()%256);
glBegin(GL_POLYGON);
glVertex2f(x+size, y+size);
glVertex2f(x-size, y+size);
glVertex2f(x-size, y-size);
glVertex2f(x+size, y-size);
glEnd();
glFlush();
}

void mouse(int btn, int state, int x, int y)
{
if(btn==GLUT_RIGHT_BUTTON)
exit(0);
if(btn==GLUT_LEFT_BUTTON && state==GLUT_DOWN)
		drawSquare(x, y);

}


void myReshape(GLsizei w, GLsizei h)
{

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, (GLdouble)w, 0.0, (GLdouble)h,
-1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glViewport(0,0,w,h);
glClearColor (0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glFlush();

ww = w; 
wh = h; 
}

void myinit(void)
{
glViewport(0,0,ww,wh);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, (GLdouble) ww, 0.0, (GLdouble) wh,
-1.0, 1.0);
glClearColor (1.0, 1.0, 1.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT);
glFlush();
}

void display(void)
{}

void mymenu(int id)
{
	if(id == 1) glClearColor(0.0,1.0,0.0,1.0);
	if(id == 2) exit(0);
}

int main(int argc, char** argv)
{
glutInit(&argc,argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
glutCreateWindow("square");
myinit ();
glutReshapeFunc (myReshape);
glutMouseFunc (mouse);
glutMotionFunc(drawSquare);
glutDisplayFunc(display);
int menu_id = glutCreateMenu(mymenu);
glutAddMenuEntry("clear Screen", 1);

glutAddMenuEntry("exit", 2);

glutAttachMenu(GLUT_RIGHT_BUTTON);

glutMainLoop();
return 0; 
}