Programming and Graphics

8.3 Drop-down menus 279

(a)(b)

Figure 8.2.2 The same Pac-Man in the original and resized window.

Problems

8.2.1. Write aGlutprogram to animate (a) a spinning, and (b) a rolling disk.

8.2.2. Write aGlutprogram to animate the snowman with his head period-

ically turning left and right.

8.3 Drop-down menus

Programming drop-down menus can be a lot of fun. The sequence of callbacks
must be designed carefully according to the OpenGL protocol.

The following code implemented in the filemenu.ccgenerates a graphics
window and produces a drop-down menu with a sub-menu that offers options for
clearing the screen, drawing a teapot or a triangle, and quitting the application:

#include <freeglut.h>

using namespace std;

void showme(void);

void showmenu(void);

void menu(int);

int win;

int menuid;

int submenuid;

int drawflag=2;