using a modeless WinForms "application" from MFC

[Dan Smith]

I'm in the process of adding a bunch of new .NET functionality to a (poorly
behaved) legacy MFC application. One of the things I'm adding is a "source
code editor" (ala VBA): the window should minimize/restore separately from
the main application, have its own menu/toolbar, etc.

The first approach was straight-forward enough: create the "application" as
a Form and use it as a modeless dialog. However, things didn't work right
with menu keyboard accelerators and the like (Ctrl-C, Alt-X, F1), apparently
a result of the main MFC application grabbing them.

So, the approach that I've been using for the past several weeks is to
create my own Application in a separate thread. See
http://discuss.develop.com/archives/wa.exe?A2=ind0401a&L=dotnet-winforms&T=0&F=&S=&P=3005
and http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=193220&SiteID=1.
This has been working reasonably well, also having to Invoke() back to the
main thread at times is a pain.

However, I'm now seeing some crashes with very strange call stacks such as:
System.OutOfMemoryException: Out of memory.
at System.Drawing.Graphics.FromHdcInternal(IntPtr hdc)
at System.Windows.Forms.PaintEventArgs.get_Graphics()
at System.Windows.Forms.Control.PaintException(PaintEventArgs e)
at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs
e, Int16 layer, Boolean disposeEventArgs)
at System.Windows.Forms.Control.WmEraseBkgnd(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.UserControl.WndProc(Message& m)
at
System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&
m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg,
IntPtr wparam, IntPtr lparam)
this seems to occur when the user tries to move my "application" window
immediately after I've Invoke()d to the main thread. Also, I'd like a
little bit better window management integration with the legacy MFC
application; for example, I don't want one of its modal (error) dialogs to
get hidden behind this editor application window.

With that extensive background; the most recent thing I've tried is to use
this top-level Form from MFC via the CWinFormsDialog<> class. After setting
TopLevel=false on my Form, the form is displayed--although the results are
quirky as I see two sets of non-client area items (close, minimize,
maximize, etc.). But the bigger problem is that I can't get the keyboard
accelerators working. I've overridden PreTranslateMessage() and tried
calling Control.PreProcessMessage() (and the like), but it doesn't seem to
work.

At this point, I'm trying to figure out where to go next: sticking with a
separate .NET Application in it's own thread is fine, but I've got no idea
what could be causing the crash above. And even then, there are still
glitches with getting windows "owned" correctly (and the legacy MFC
application has it's own ideas too).

Switching to MFC for at least some of the "application" shell (although as
absolutely little as possible in MFC!) might help, but not if I can't get
the keyboard accelerators. Is what I'm trying to do in MFC possible?
supported? If not, what are the alternatives? My .NET UI has docking
windows and MDI; I *really* don't want to have to do all that "shell" in
MFC--even if the content are WinForms controls.

Thanks for any tips/advice/pointers/etc.

Dan

 

[Sheng Jiang[MVP]]

I remember a while ago I have a demo app in which I have my CHTMLView based
app work on a windows form message pump... basically override CWinApp::Run
and call Application::Start instead of calling CWinThread::Run . To make
PretranslateMessage work I added my own IMessageFilter implementation to the
application and call MFC's CWinApp:reTranslateMessage in it. Haven't
tested it extensively, though.

 

[Sheng Jiang[MVP]]

code

// CMFCWinFormHybridApp initialization
#pragma managed
extern void ManagedInit();
#pragma unmanaged
BOOL CMFCWinFormHybridApp::InitInstance()
{
ManagedInit();
....

#pragma managed
bool MFCMessageFilter(HWND hwnd,UINT message,LONG x,LONG y,DWORD time,
WPARAM wparam, LPARAM lparam)
{
_AFX_THREAD_STATE *pState = AfxGetThreadState();

pState->m_msgCur.hwnd=hwnd;
pState->m_msgCur.message=message;
pState->m_msgCur.pt.x=x;
pState->m_msgCur.pt.y=y;
pState->m_msgCur.time=time;
pState->m_msgCur.wParam=wparam;
pState->m_msgCur.lParam=lparam;
if(message==WM_KICKIDLE)
return true;
bool mfcPretranslate=(bool)AfxPreTranslateMessage(&(pState->m_msgCur));
return mfcPretranslate;
}
ref class CMFCMessageFilterublic System::Windows::Forms::IMessageFilter
{
public:

[System::Security:ermissions::SecurityPermission(System::Security:ermiss
ions::SecurityAction::LinkDemand,
Flags=System::Security:ermissions::SecurityPermissionFlag::UnmanagedCode)]
virtual bool PreFilterMessage(System::Windows::Forms::Message % m)
{
return
MFCMessageFilter((HWND)m.HWnd.ToPointer(),m.Msg,0,0,0,(WPARAM)m.WParam.ToPoi
nter(),(LPARAM)m.LParam.ToPointer());
}
};
void ManagedInit()
{
System::Windows::Forms::Application::AddMessageFilter(gcnew
CMFCMessageFilter());
}
void ManagedRun()
{
System::Windows::Forms::Application::Run();
}


#pragma unmanaged


int CMFCWinFormHybridApp::Run()
{
if (m_pMainWnd == NULL && AfxOleGetUserCtrl())
{
// Not launched /Embedding or /Automation, but has no main window!
TRACE(traceAppMsg, 0, "Warning: m_pMainWnd is NULL in CWinApp::Run -
quitting application.\n");
AfxPostQuitMessage(0);
}
ManagedRun();
return ExitInstance();
//return CWinApp::Run();
}