C / C++ / MFC

// CListCtrlEx.h
afx_msg void OnHdnItemclick(NMHDR* pNMHDR, LRESULT* pResult);

// CListCtrlEx.cpp
	ON_NOTIFY_REFLECT(LVN_COLUMNCLICK, CListCtrlEx::OnHdnItemclick)
...
...

void CListCtrlEx::OnHdnItemclick(NMHDR* pNMHDR, LRESULT* pResult)
{
	NM_LISTVIEW* phdr = reinterpret_cast<NM_LISTVIEW*>(pNMHDR);
	SortOnColumn(phdr->iSubItem, TRUE);
	*pResult = 0;
}

// CTestList5View.h
	afx_msg void OnHdnItemclickList1(NMHDR* pNMHDR, LRESULT* pResult);

	ON_NOTIFY(LVN_COLUMNCLICK, IDC_LIST1, OnHdnItemclickList1)
...
...
void CTestList5View::OnHdnItemclickList1(NMHDR* pNMHDR, LRESULT* pResult) 
{
	NM_LISTVIEW* phdr = reinterpret_cast<NM_LISTVIEW*>(pNMHDR);
	// TODO: Add your control notification handler code here

	CString sTemp;
	sTemp.Format("%d",phdr->iSubItem);
	TRACE("\n column %s\n",sTemp);

	*pResult = 0;
}

// this is passed to RegisterClassExW
static LRESULT CALLBACK mWindow::WndProc(IN HWND hwnd, 
					 IN UINT uMsg, 
					 IN WPARAM wParam, 
					 IN LPARAM lParam)
{
	mWindow *self;
	if (uMsg == WM_NCCREATE) {
		LPCREATESTRUCT lpcs = (LPCREATESTRUCT)lParam;
		self = (mWindow *)lpcs->lpCreateParams;
		SetWindowLongPtr(hwnd, GWLP_USERDATA, (LPARAM)self);
	} 
	else 
	{
		self = (mWindow *)GetWindowLongPtr(hwnd, GWLP_USERDATA);
	}
	if (self) 
	{
		return self->InternalWndProc(hwnd, uMsg, wParam, lParam); // this is my first wndproc
	} 
	else 
	{
		return DefWindowProc(hwnd, uMsg, wParam, lParam);
	}
}

__w64 long __stdcall InternalWndProc(IN HWND hWnd, 
				IN unsigned int msg, 
				 IN __w64 unsigned int wParam, 
				 IN __w64 long lParam)
{
    switch(msg)
    {
         // here i am doing some pre painting, glass, background image, window moving handler, etc
          case wm_paint: 
              OnPaint(); // inside OnPaint (among other things) i am saving current HDC, which then can be exported from class
                         // like this: myWindow->operator HDC();
          break;
          default:
	         return _outer_procedure(hWnd, msg, wParam, lParam);
	}
return _outer_procedure(hWnd, msg, wParam, lParam); // this is my second wndproc, which outside a class
}

// so when "msg" is processed, this wndproc "jumps" to wndproc outside a class ->

__w64 long __stdcall WndProc(IN HWND hWnd,  // this is my "_outer_procedure"
				IN unsigned int msg, 
				IN __w64 unsigned int wParam, 
				IN __w64 long lParam)
{
    switch(msg)
    {
         case WM_PAINT: // and now i am simply trying to draw a single black line
		{
			Gdiplus::Graphics graphics((HDC)AppWindow->operator HDC());
			Gdiplus::Pen      pen(Gdiplus::Color::Black);
			graphics.DrawLine(&pen, 100, 100, 200, 100);
		}
		break; // which fails badly, and there is no difference, if i do BeginPaint / EndPaint or simply 
//import hdc from a class. while inporting HDC - it has same address in memory like in class
    }
}