need some help with opengl

[number87]

Hi I am new to openGL, just picked it up recently and I am trying to do a program window which draws a small square wherever the mouse cursor clicks. Below is the code which I came up with and I dont know why it wont draw the square when I click. Maybe I got the logic wrong inside?

GLint winWidth, winHeight;

void init()
{
  glClearColor(1.0f, 1.0f, 1.0f, 1.0f); //clears background colour to white
  glClear(GL_COLOR_BUFFER_BIT);      //clear the colour buffer to the colour previously set in glClearColor 
  
}


void renderScene()
{
     glFlush();
}


void winResize(GLsizei width, GLsizei height)
{
     GLfloat aspectRatio;
     winWidth = width;
  winHeight = height;

     
     if(height == 0)//prevent zero division
        height = 1;    
     
     //set viewport to window dimensions
     glViewport(0, 0, width, height);
     
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
     
     aspectRatio = (GLfloat)width/(GLfloat)height;
     
     if(width <= height)
        glOrtho(-100.0, 100.0, -100.0/aspectRatio, 100.0/aspectRatio, 1.0, -1.0);
     
     else
        glOrtho(-100.0*aspectRatio, 100.0*aspectRatio, -100.0, 100.0, 1.0, -1.0);
        
        
     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity();
     
}

void mouseCallback(int button, int state, int x, int y)
{
     if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
        {
               y = winHeight-y; /* invert y position */
               glColor3ub(static_cast<char>(rand()%256), static_cast<char>(rand()%256), static_cast<char>(rand()%256)); /* a random color */
               glBegin(GL_POLYGON);
               glVertex2f(x+3, y+3);
               glVertex2f(x-3, y+3);
               glVertex2f(x-3, y-3);
               glVertex2f(x+3, y-3);
               glEnd();

               glutPostRedisplay();
        }
     
}


int main()
{
     glutInitDisplayMode(GLUT_RGB);	    
     glutCreateWindow("Assessment 1");	        
     
     glutDisplayFunc(renderScene);					            
     glutReshapeFunc(winResize);	
     
     init();  
     glutMouseFunc(mouseCallback);
     glutMainLoop();
     
     return 0;
}