C2440 Can't convert LRESULT to WNDPROC in C++ WinApi - c++

Question

I'm trying to write this win32 program with WinApi and I'm stuck because the tutorial I'm following seems to have a problem.
MainWindow.h:
class MainWindow
{
public:
MainWindow(HINSTANCE);
~MainWindow(void);
LRESULT CALLBACK WndProcedure(HWND, UINT, WPARAM, LPARAM);
// [...]
MainWindow.cpp:
MainWindow::MainWindow(HINSTANCE hInstance) : hwnd(0)
{
WNDCLASSEX WndClsEx;
// [...]
WndClsEx.lpfnWndProc = &MainWindow::WndProcedure;
// [...]
}
LRESULT CALLBACK MainWindow::WndProcedure(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
// [...]
}
I must be referencing MainWindow::WndProcedure wrong because I'm following the signature exactly as the tutorial says, however the lpfnWndProc line in the constructor gives a compile-time error:
error C2440: '=' : cannot convert from 'LRESULT (__stdcall MainWindow::* )(HWND,UINT,WPARAM,LPARAM)' to 'WNDPROC'

Answer 1

replace
LRESULT CALLBACK WndProcedure(HWND, UINT, WPARAM, LPARAM);
by
static LRESULT CALLBACK WndProcedure(HWND, UINT, WPARAM, LPARAM);
The this pointer is a hidden parameter in your function call and by declaring it static the this pointer is not a parameter anymore and the signature of the two functions match.

Answer 2

That's because your WndProcedure function must be either a global function or a static member function.

Answer 3

You can't use a non-static member function as a window procedure. If you declare WndProcedure as static it should compile. A non-member function would work as well.
Non-static member functions have a different signature than static members. This is because they receive an implicit this parameter in addition to the explicitly defined parameters.