WndProc as a class member, fails to quit - c++

Question

I want to make WndProc a class member function and I found this article, so I tried to apply it to the simplest Win32 program, which does nothing but creating a blank window, the very first step of Win32.
int Myclass::Start(HINSTANCE hInstance, int nCmdShow)
{
if (FAILED(InitWindow(hInstance, nCmdShow)))
return 0;
MSG msg = { 0 };
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return (int)msg.wParam;;
}
LRESULT Myclass::StaticWndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
Myclass* pThis = nullptr;
if (message == WM_NCCREATE) {
LPCREATESTRUCT lpcs = reinterpret_cast<LPCREATESTRUCT>(lParam);
pThis = static_cast<Myclass*>(lpcs->lpCreateParams);
SetWindowLongPtr(hWnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(pThis));
}
else {
pThis = reinterpret_cast<Myclass*>(GetWindowLongPtr(hWnd, GWLP_USERDATA));
}
if(pThis)
return pThis->RealWndProc(hWnd, message, wParam, lParam);
return DefWindowProc(hWnd, message, wParam, lParam);
}
LRESULT Myclass::RealWndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
PAINTSTRUCT ps;
HDC hdc;
switch (message)
{
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
EndPaint(hWnd, &ps);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
It runs well, but when I close the window the program stays in the message loop and doesn't quit.
I found out that WM_DESTROY is not delivered to RealWndProc(), so PostQuitMessage() is not called.
If I insert if(WM_DESTROY == message) { PostQuitMessage(0); return 0; } right before the last line of StaticWndProc, then the program quits. But I'm not sure if this is a good way to do it.
How can I make WM_DESTROY consumed by RealWndProc()?

Answer 1

Like this is how I did it.. Works just fine.. The only problem I can think of in your code is one of two:
You missed the calling convention for the WindowProcedure.
You forgot to pass "this" to CreateWindowEx.
And the code:
#include <windows.h>
class Window
{
public:
Window(LPCTSTR Title, LPCTSTR Class, DWORD dwStyleEx = 0, DWORD dwStyle = WS_OVERLAPPEDWINDOW,
POINT Location = {CW_USEDEFAULT, CW_USEDEFAULT}, int Width = CW_USEDEFAULT,
int Height = CW_USEDEFAULT, HWND Parent = HWND_DESKTOP, HMENU Menu = nullptr);
int Loop();
private:
HWND WindowHandle;
static LRESULT __stdcall WindowProcedure(HWND Hwnd, UINT Msg, WPARAM wParam, LPARAM lParam);
LRESULT RealWindowProcedure(HWND Hwnd, UINT Msg, WPARAM wParam, LPARAM lParam);
};
Window::Window(LPCTSTR Title, LPCTSTR Class, DWORD dwStyleEx, DWORD dwStyle, POINT Location, int Width, int Height, HWND Parent, HMENU Menu)
{
WNDCLASSEX WndClass =
{
sizeof(WNDCLASSEX), CS_DBLCLKS, Window::WindowProcedure,
0, 0, GetModuleHandle(nullptr), LoadIcon(nullptr, IDI_APPLICATION),
LoadCursor(nullptr, IDC_ARROW), HBRUSH(COLOR_BACKGROUND),
nullptr, Class, LoadIcon(nullptr, IDI_APPLICATION)
};
if(RegisterClassEx(&WndClass))
{
WindowHandle = CreateWindowEx(dwStyleEx, Class, Title, dwStyle, Location.x, Location.y, Width, Height, Parent, Menu, GetModuleHandle(nullptr), this);
}
}
LRESULT __stdcall Window::WindowProcedure(HWND Hwnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
Window* Data = nullptr;
switch(Msg)
{
case WM_NCCREATE:
{
CREATESTRUCT* pCreate = reinterpret_cast<CREATESTRUCT*>(lParam);
Data = static_cast<Window*>(pCreate->lpCreateParams);
SetWindowLongPtr(Hwnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(Data));
break;
}
default:
{
Data = reinterpret_cast<Window*>(GetWindowLongPtr(Hwnd, GWLP_USERDATA));
break;
}
}
return Data ? Data->RealWindowProcedure(Hwnd, Msg, wParam, lParam) : DefWindowProc(Hwnd, Msg, wParam, lParam);
}
LRESULT Window::RealWindowProcedure(HWND Hwnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
switch(Msg)
{
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(Hwnd, Msg, wParam, lParam);
}
return 0;
}
int Window::Loop()
{
MSG Messages = {nullptr};
ShowWindow(WindowHandle, SW_SHOW);
while(GetMessage(&Messages, nullptr, 0, 0))
{
TranslateMessage(&Messages);
DispatchMessage(&Messages);
}
return Messages.wParam;
}
int main()
{
Window w("TItle", "Class");
return w.Loop();
}

Answer 2

You should catch WM_CLOSE and have it call DestroyWindow() to trigger WM_DESTROY:
case WM_CLOSE:
DestroyWindow(hWnd);
break;
Also, your StaticWndProc() method is using the wrong calling convention. It must use the __stdcall calling convention, which is wrapped by WINAPI and CALLBACK macros, eg:
LRESULT CALLBACK Myclass::StaticWndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)