The problem is that a pointer to an instance bound member function has to include the this pointer. OpenGL is a C API, and knows nothing about this pointers. You'll have to use a static member function (which doesn't require an instance, and thus no this), and set some static data members (to access the instance) in order to use glutDisplayFunc.
class myPixmap
{
private:
static myPixmap* currentInstance;
static void drawCallback()
{
currentInstance->draw();
}
void setupDrawCallback()
{
currentInstance = this;
::glutDisplayFunc(myPixmap::drawCallback);
}
};
You may also have problems with C linkage vs C++ linkage, in which case you'll have to play around with extern "C". If so, you might have to use a global function, rather than a static member function as your callback, and have that call myPixmap::draw. Something like:
class myPixmap
{
public:
void draw();
private:
void setupDrawCallback();
};
myPixmap* g_CurrentInstance;
extern "C"
void drawCallback()
{
g_CurrentInstance->draw();
}
void myPixmap::setupDrawCallback();
{
::g_CurrentInstance = this;
::glutDisplayFunc(::drawCallback);
}
With all of this, try to make as few changes as possible, since this is really kind of a kludge to deal w/ OpenGL being a C API.
If you want multiple instances (I don't think most people using GLUT make multiple instances, but maybe you are), you'll have to figure out a solution using a std::map to retrieve the instance:
static std::map<int, myPixmap> instanceMap;
Where you'd get the int to resolve which instance, I am not sure :)
FYI, you should define functions that take no parameters this way:
void some_function() { }
not
void some_function(void) { }