MFC Modeless dialog hangs

[zuhrs]

In a 3rd party application I want to invoke an MFC dll which creates a modeless dialog.
The below is the exported function:

long CAPLEXPORT far CAPLPASCAL ShowTstDlg(long a, long b, long c)
{
TstDlg* pTest = new TstDlg;
pTest->Create(TstDlg::IDD, NULL);
pTest->ShowWindow(SW_SHOW);
return 1;
}

in the above code, the modeless dialog freezes.

So I have modified the code as follows:

long CAPLEXPORT far CAPLPASCAL ShowTstDlg(long a, long b, long c)
{
TstDlg* pTest = new TstDlg;
pTest->Create(TstDlg::IDD, NULL);
pTest->ShowWindow(SW_SHOW);


CString str("MQB RBS Menu");
HANDLE hEvent = CreateEvent(NULL, TRUE, FALSE, str);

MSG msg;
while(WaitForSingleObject(hEvent, 0) != WAIT_OBJECT_0)
{
while(::GetMessage(&msg, NULL, 0, 0))
{
::TranslateMessage(&msg);
:ispatchMessage(&msg);
}
}

// event cleanup
CloseHandle(hEvent);

return 1;
}

In this case, the modeless dialog works fine, but the 3rd part application hangs as the control is never returned to the 3rd party application, due to infinite while loop.


So I changed as follows:


long CAPLEXPORT far CAPLPASCAL ShowTstDlg(long a, long b, long c)
{
TstDlg* pTest = new TstDlg;
pTest->Create(TstDlg::IDD, NULL);
pTest->ShowWindow(SW_SHOW);


CString str("MQB RBS Menu");
HANDLE hEvent = CreateEvent(NULL, TRUE, FALSE, str);

MSG msg;
while(WaitForSingleObject(hEvent, 0) != WAIT_OBJECT_0)
{
if(GetActiveWindow() != pTest->GetSafeHwnd()) break
while(::GetMessage(&msg, NULL, 0, 0))
{
if(GetActiveWindow() != pTest->GetSafeHwnd()) break
::TranslateMessage(&msg);
:ispatchMessage(&msg);
}
}

// event cleanup
CloseHandle(hEvent);

return 1;
}

In this case the menu is active at first. Later when I click on any other application, the again the dialog freezez.

Can I know how can this be solved?

Thanks in advance

[GCDEF]

39 posts is enough to have discovered code tags by now.

If the problem is that your GetMessageLoop never exists, try PeekMessage with the PM_REMOVE flag instead.

I won't believe WaitForSingleObject should be in a loop either

[zuhrs]

Thanks for the quick reply

I have even tried the PeekMessage as follows

MSG msg; // handle dialog messages
while(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
if(!IsDialogMessage(hwnd,&msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}

In this case also the Modeless dialog freezes, but the parent is active.

[darwen]

I'm presuming that the 3rd party application is executing a long running task when it calls your callback ?

Also is the 3rd party application a Windows application or a console application ? I'm assuming that it's a console application which is why you're trying to write your own message loop.

The thing to realise is that windows messages are dispatched on a single thread - so if a long running task is executing on the UI thread then all the UI will hang since the message loop will never be processed.

One thing to try is to run up a separate thread and then call DoModal() on your dialog in the separate thread. This may work - DoModal() contains its own message loop.

Darwen.

[zuhrs]

Thanks for the reply.

Actually third party application is a windows application, but it is being developed using KEPL (Not a Microsoft language), which is used for a simulation of embedded programming

Can you please give a link to create a separate thread to launch modal dialog ( As i am a learner programmer in MFC).

[zuhrs]

I have created a ModalDialog using thread

void CMenuDlg::OnBnClickedOk()
{


HANDLE hCommReadThread = CreateThread(NULL, 0, ThreadFunc, NULL, 0, NULL);
//hCommReadThread = CreateThread(NULL, 0, ThreadFunc, NULL, 0, NULL);

if (hCommReadThread != NULL)
{
CloseHandle(hCommReadThread);
hCommReadThread = NULL;
}

return;
}

DWORD WINAPI ThreadFunc(LPVOID lParam)
{
//Ctest oTest; Declared globally
oTest.DoModal();

return 1;
}

How can I now close the dialog on click of some button?

[darwen]

Click of some button

Is the button in the main ui ? Call another method like the one you've got and call

oTest.Close();

Close button on the dialog itself should work ok (i.e. cross at top right hand side of the window).

Darwen.

P.S. Before I start getting flamed here I'd just like to say that this is not a generally acceptible way of doing this. What you should really be doing is running the long-running task in its own thread and keeping all UI on its own thread. However I am assuming you don't have control over this as it's in a 3rd party application.