Why can't my WndProc be in a class?

Question

This seems like it should be pretty straightforward. I have my class:

class Simple
{
public:
    LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPA         


        

Answer 1

// Header  
class Foo   
{  
public:
  Foo();   

  ~Foo();  

  static LRESULT CALLBACK WinProc(HWND, UINT, WPARAM, LPARAM);

private:
  LRESULT CALLBACK MyWinProc(HWND, UINT, WPARAM, LPARAM);

  static Foo *m_pInstance;
}

// Implementation

#include "Foo.h"

Foo * Foo::m_pInstance = NULL;

Foo::Foo()
{  
  m_pInstance = this;   
}  

Foo::~Foo()
{
}

LRESULT CALLBACK Foo::WinProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)  
{  
  return m_pInstance->MyWinProc(hWnd, message, wParam, lParam);  
}  

LRESULT CALLBACK Foo::MyWinProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)  
{  
  return DefWindowProc(hWnd, message, wParam, lParam);  
}