Re: [Boost-users] function/bind - passing function pointer to C API

From: Cédric Venet (cedric.venet_at_[hidden])
Date: 2007-08-16 03:19:28

Quoting Nicholas Yue <yue.nicholas_at_[hidden]>:

> Hi,
>
>     I am attempting to use Boost bind and function to help me pass a member
> function as a function pointer to the GLUT C-library.
>
>   I have difficulty understanding the usage of bind and function in the
> Boost library. When I attempt to pass what I thought was a function pointer,
> the compiler indicated that it is actually not a function pointer.

because the result of a bind is a functor not a function pointer. A  
functor is a class which define operator() so that you can use it like  
a function.

To have a call back in a C librairie, you need a static function  
pointeur, something which is defined globaly and which can't have  
parameter bind to it.

If you have only one instance of MyGlut, then you can just do:

>
> class MyGlut {
> public:
>   MyGlut();
>   virtual ~MyGlut();
>   void loop(int argc, char **argv);
>   void draw(void);
     static void displayFunc(boost::function<void()> func);
> private:
     static void displayCallbackFwd() { display_callback(); }
> private:
     static boost::function<void()> display_callback;
> };
>
> void MyGlut::displayFunc(boost::function<void()> func)
> {
     display_callback = func;
     glutDisplayFunc(MyGlut::displayCallbackFwd);
> }
>
> void MyGlut::loop(int argc, char **argv)
> {
>   glutInit(&argc,argv);
>   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH |
> GLUT_MULTISAMPLE);
>   glutCreateWindow("Hello World");
>
>   //glutDisplayFunc(redraw); // Original way to pass C-function pointer
>   displayFunc( boost::bind(&MyGlut::draw, *this) );
>
> }
>
> Regards
>