void createPopupMenus() {

    shrinkMenu = glutCreateMenu(processShrinkMenu);

    glutAddMenuEntry("Shrink",SHRINK);

    glutAddMenuEntry("NORMAL",NORMAL);

    fillMenu = glutCreateMenu(processFillMenu);

    glutAddMenuEntry("Fill",FILL);

    glutAddMenuEntry("Line",LINE);

    colorMenu = glutCreateMenu(processColorMenu);

    glutAddMenuEntry("Red",RED);

    glutAddMenuEntry("Blue",BLUE);

    glutAddMenuEntry("Green",GREEN);

    glutAddMenuEntry("Orange",ORANGE);

    mainMenu = glutCreateMenu(processMainMenu);

    glutAddSubMenu("Polygon Mode", fillMenu);

    glutAddSubMenu("Color", colorMenu);

    // attach the menu to the right button

    glutAttachMenu(GLUT_RIGHT_BUTTON);

}