glut, classes, game (serious shit, check it out)

[marcos3131]

Hi, I've created class "Game" and I use GLUT.
GLUT's function:
glutDisplayFunc() takes a pointer to a rendering function.

I need to declare this function somewhere and I want to be able to deliver this function to glutDisplayFunc().

I want class "Game" not to enable this function outside. In other words, I want to encapsulate it.

Can someone help?

[jsmith]

Declare it in the class' protected or private section, however it will have to be static, because glutDisplayFunc cannot take member functions as parameters.

[marcos3131]

Thx for reply jsmith,
but I need this function to be non static, cause I want to modify private members in "Game" class.

If it's imposible to go that way, what can be the best walkaroud for this?
You know, I'd rather work on classes.

[jsmith]

If glutDisplayFunc() has a void* parameter you can specify that gets passed to the callback function, then pass it the
"this" pointer of the object. Then the callback has to reinterpret_cast the void* to a pointer-to-object. That's your
only option.

[marcos3131]

Actually declaration of the glut function is:
void glutDisplayFunc(void (*func)(void));

It's not void *.

[marcos3131]

Thx again.
The fast solution:
http://bytes.com/topic/c/answers/441511-registering-glut-callback-c

[ne555]

http://www.parashift.com/c++-faq-lite/pointers-to-members.html#faq-33.2

If you don't want a global variable

typedef void (*callback)();
class Game;
struct aux{
	aux(Game *a){
		obj = a;
	}
	
	static Game *obj;
	static void display(){
		obj->display();
	}
	callback get(){
		return aux::display;
	}
};
Game* aux::obj;

//calling
glutDisplayFunc( aux(game_pointer).get() );