Extract reusable part of the MFC sample in a header

Allow reusing this functionality from outside the library, it can he
useful if an MFC window needs to be embedded into a wx application (or
vice versa).

Also use a better wxEntryStart() overload as a side effect, this should,
in particular, fix the problem with command line arguments processing in
mixed MFC/wx applications pointed out in a comment in the sample
previously.

include/wx/msw/mfc.h

@@ -0,0 +1,137 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/msw/mfc.h
+// Purpose:     Helpers for applications using both wxWidgets and MFC
+// Author:      Julian Smart, Vadim Zeitlin
+// Created:     2017-12-01 (mostly extracted from samples/mfc)
+// Copyright:   (c) 2017 Vadim Zeitlin <vadim@wxwidgets.org>
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_MSW_MFC_H_
+#define _WX_MSW_MFC_H_
+
+#ifndef __AFXWIN_H__
+    #error "MFC headers must be included before including this file."
+#endif
+
+#include "wx/app.h"
+#include "wx/evtloop.h"
+#include "wx/window.h"
+#include "wx/msw/winundef.h"
+
+// ----------------------------------------------------------------------------
+// MFC window class wrapping a window created by wxWidgets
+// ----------------------------------------------------------------------------
+
+class wxMFCWnd : public CWnd
+{
+public:
+    explicit wxMFCWnd(wxWindow* w)
+    {
+        Attach(w->GetHWND());
+    }
+
+    ~wxMFCWnd()
+    {
+        // Prevent MFC from destroying the wxWindow.
+        Detach();
+    }
+};
+
+// ----------------------------------------------------------------------------
+// MFC application class forwarding everything to wxApp
+// ----------------------------------------------------------------------------
+
+class wxMFCWinApp : public CWinApp
+{
+public:
+    BOOL InitInstance() wxOVERRIDE
+    {
+        if ( !CWinApp::InitInstance() )
+            return FALSE;
+
+        if ( !wxEntryStart(m_hInstance) )
+            return FALSE;
+
+        if ( !wxTheApp || !wxTheApp->CallOnInit() )
+            return FALSE;
+
+        if ( !InitMainWnd() )
+            return FALSE;
+
+        return TRUE;
+    }
+
+    int ExitInstance() wxOVERRIDE
+    {
+        delete m_pMainWnd;
+
+        if ( wxTheApp )
+            wxTheApp->OnExit();
+
+        wxEntryCleanup();
+
+        return CWinApp::ExitInstance();
+    }
+
+    // Override this to provide wxWidgets message loop compatibility
+    BOOL PreTranslateMessage(MSG *msg) wxOVERRIDE
+    {
+        wxEventLoop * const
+            evtLoop = static_cast<wxEventLoop *>(wxEventLoop::GetActive());
+        if ( evtLoop && evtLoop->PreProcessMessage(msg) )
+            return TRUE;
+
+        return CWinApp::PreTranslateMessage(msg);
+    }
+
+    BOOL OnIdle(LONG lCount) wxOVERRIDE
+    {
+        BOOL moreIdle = CWinApp::OnIdle(lCount);
+
+        if ( wxTheApp && wxTheApp->ProcessIdle() )
+            moreIdle = TRUE;
+
+        return moreIdle;
+    }
+
+protected:
+    // This virtual method can be overridden to create the main window using
+    // MFC code. The default implementation relies on wxApp::OnInit() creating
+    // a top level window which is then wrapped in an MFC window and used as
+    // the main window.
+    virtual BOOL InitMainWnd()
+    {
+        wxWindow* const w = wxTheApp->GetTopWindow();
+        if ( !w )
+            return FALSE;
+
+        // We need to initialize the main window to let the program continue
+        // running.
+        m_pMainWnd = new wxMFCWnd(w);
+
+        // And we need to let wxWidgets know that it should exit the
+        // application when this window is closed, as OnRun(), which does this
+        // by default, won't be called when using MFC main message loop.
+        wxTheApp->SetExitOnFrameDelete(true);
+
+        return TRUE;
+    }
+};
+
+// ----------------------------------------------------------------------------
+// wxWidgets application class to be used in MFC applications
+// ----------------------------------------------------------------------------
+
+class wxAppWithMFC : public wxApp
+{
+public:
+    void ExitMainLoop() wxOVERRIDE
+    {
+        // There is no wxEventLoop to exit, tell MFC to stop pumping messages
+        // instead.
+        ::PostQuitMessage(0);
+    }
+};
+
+#endif // _WX_MSW_MFC_H_

samples/mfc/mfctest.cpp

@@ -17,8 +17,8 @@
 // created subsequently.
 //
 // (1) Make MyApp::OnInit not create a main window.
-// (2) Make MFC's InitInstance create a main window, and remove
+// (2) Define a class deriving from wxMFCWinApp and override its InitMainWnd()
-//     creation of CDummyWindow.
+//     to create the main window in MFC code.
 //
 // This can be accomplished by setting START_WITH_MFC_WINDOW to 1 below.
 
@@ -73,6 +73,8 @@
 #include "wx/nativewin.h"
 #include "wx/spinctrl.h"
 
+#include "wx/msw/mfc.h"
+
 #include "resource.h"
 
 #include "mfctest.h"
@@ -82,19 +84,15 @@
 // theApp:
 // Just creating this application object runs the whole application.
 //
-CTheApp theApp;
+SampleMFCWinApp theApp;
 
 // wxWidgets elements
 
-// Define a new application type
+// Define a new application type inheriting from wxAppWithMFC
-class MyApp: public wxApp
+class MyApp: public wxAppWithMFC
 {
 public:
-    virtual bool OnInit();
+    virtual bool OnInit() wxOVERRIDE;
-
-    // we need to override this as the default behaviour only works when we're
-    // running wxWidgets main loop, not MFC one
-    virtual void ExitMainLoop();
 
     wxFrame *CreateFrame();
 };
@@ -238,73 +236,6 @@ ON_COMMAND( IDM_TEST, OnTest )
 //}}AFX_MSG_MAP
 END_MESSAGE_MAP()
 
-BOOL CTheApp::InitInstance()
-{
-    if ( !CWinApp::InitInstance() )
-        return FALSE;
-
-    // TODO: cmd line parsing
-    WXDLLIMPEXP_BASE void wxSetInstance(HINSTANCE hInst);
-    wxSetInstance(m_hInstance);
-    wxApp::m_nCmdShow = m_nCmdShow;
-    int argc = 0;
-    wxChar **argv = NULL;
-    wxEntryStart(argc, argv);
-    if ( !wxTheApp || !wxTheApp->CallOnInit() )
-        return FALSE;
-
-#if START_WITH_MFC_WINDOW
-    // Demonstrate creation of an initial MFC main window.
-    m_pMainWnd = new CMainWindow();
-    m_pMainWnd->ShowWindow( m_nCmdShow );
-    m_pMainWnd->UpdateWindow();
-#else
-    // Demonstrate creation of an initial wxWidgets main window.
-    // Wrap wxWidgets window in a dummy MFC window and
-    // make the main window.
-    if (wxTheApp && wxTheApp->GetTopWindow())
-    {
-        m_pMainWnd = new CDummyWindow((HWND) wxTheApp->GetTopWindow()->GetHWND());
-    }
-#endif
-
-    return TRUE;
-}
-
-int CTheApp::ExitInstance()
-{
-#if !START_WITH_MFC_WINDOW
-    delete m_pMainWnd;
-#endif
-
-    if ( wxTheApp )
-        wxTheApp->OnExit();
-    wxEntryCleanup();
-
-    return CWinApp::ExitInstance();
-}
-
-// Override this to provide wxWidgets message loop compatibility
-BOOL CTheApp::PreTranslateMessage(MSG *msg)
-{
-    wxEventLoop * const
-        evtLoop = static_cast<wxEventLoop *>(wxEventLoop::GetActive());
-    if ( evtLoop && evtLoop->PreProcessMessage(msg) )
-        return TRUE;
-
-    return CWinApp::PreTranslateMessage(msg);
-}
-
-BOOL CTheApp::OnIdle(LONG lCount)
-{
-    BOOL moreIdle = CWinApp::OnIdle(lCount);
-
-    if ( wxTheApp && wxTheApp->ProcessIdle() )
-        moreIdle = TRUE;
-
-    return moreIdle;
-}
-
 /*********************************************************************
 * wxWidgets elements
 ********************************************************************/
@@ -315,22 +246,12 @@ bool MyApp::OnInit()
         return false;
 
 #if !START_WITH_MFC_WINDOW
-    // as we're not inside wxWidgets main loop, the default logic doesn't work
-    // in our case and we need to do this explicitly
-    SetExitOnFrameDelete(true);
-
     (void) CreateFrame();
 #endif
 
     return true;
 }
 
-void MyApp::ExitMainLoop()
-{
-    // instead of existing wxWidgets main loop, terminate the MFC one
-    ::PostQuitMessage(0);
-}
-
 wxFrame *MyApp::CreateFrame()
 {
     MyChild *subframe = new MyChild(NULL, wxT("Canvas Frame"), wxPoint(10, 10), wxSize(300, 300),
@@ -451,17 +372,3 @@ void MyChild::OnActivate(wxActivateEvent& event)
     if (event.GetActive() && canvas)
         canvas->SetFocus();
 }
-
-// Dummy MFC window for specifying a valid main window to MFC, using
-// a wxWidgets HWND.
-CDummyWindow::CDummyWindow(HWND hWnd)
-{
-    Attach(hWnd);
-}
-
-// Don't let the CWnd destructor delete the HWND
-CDummyWindow::~CDummyWindow()
-{
-    Detach();
-}
-

samples/mfc/mfctest.h

@@ -9,11 +9,7 @@
 #ifndef __MFCTEST_H__
 #define __MFCTEST_H__
 
-/////////////////////////////////////////////////////////////////////////////
+// CMainWindow: just a normal MFC window class.
-
-// CMainWindow:
-// See hello.cpp for the code to the member functions and the message map.
-//
 class CMainWindow : public CFrameWnd
 {
 public:
@@ -31,30 +27,30 @@ private:
     class wxNativeContainerWindow* m_containerWX;
 };
 
-// A dummy CWnd pointing to a wxWindow's HWND
+#if START_WITH_MFC_WINDOW
-class CDummyWindow: public CWnd
+
+// There is no need to define an application class if the default behaviour of
+// using the wxWindow created in wxApp::OnInit() as main window is acceptable,
+// but if we want to create the initial window in MFC, we need this class in
+// order to override InitMainWnd() in it.
+class SampleMFCWinApp : public wxMFCWinApp
 {
-  public:
+protected:
-    CDummyWindow(HWND hWnd);
+    BOOL InitMainWnd() wxOVERRIDE
-    ~CDummyWindow(void);
+    {
+        // Demonstrate creation of an initial MFC main window.
+        m_pMainWnd = new CMainWindow();
+        m_pMainWnd->ShowWindow( m_nCmdShow );
+        m_pMainWnd->UpdateWindow();
+
+        return TRUE;
+    }
 };
 
-/////////////////////////////////////////////////////////////////////////////
+#else // !START_WITH_MFC_WINDOW
 
-// CTheApp:
+typedef wxMFCWinApp SampleMFCWinApp;
-//
-class CTheApp : public CWinApp
-{
-public:
-    BOOL InitInstance();
-    int ExitInstance();
 
-    // Override this to provide wxWidgets message loop
+#endif // START_WITH_MFC_WINDOW/!START_WITH_MFC_WINDOW
-    // compatibility
-    BOOL PreTranslateMessage(MSG *msg);
-    BOOL OnIdle(LONG lCount);
-};
-
-/////////////////////////////////////////////////////////////////////////////
 
 #endif // __MFCTEST_H__