Programming and Graphics

270 Introduction to C++ Programming and Graphics

//--- keyboard:

void keyboard(unsigned char key, int x, int y)

{

cout <<"Please enter a number:"<<endl;

cin >> a;

//--- mouse:

void mouse(int button, int state, int x, int y)

{

a=-1000000;

}

//--- add:

void add(void)

{

a=a+1;

cout << a << endl;

}

Idle functions find important applications in window resizing and animation.

Event callbacks

Following is a summary of callbacks triggered by events:

void glutDisplayFunc(void (*func)(void));

This callback specifies the function to be executed when the window is

shown for the first time, popped up, or otherwise redrawn.

void glutPostRedisplay(void);

This callback prompts the execution of the function defined by

theglutPostDisplayFunccallback at the first available opportunity, sig-

naling a need for redraw.

void glutIdleFunc(void (*func)(void));

This callback specifies the function to be executed between events and

finds important applications in animation.

void glutMouseFunc(void (*func)(int btn, int state, int x, int y));