CDialog::Create failing.

[Perdrix]

I have code that is called from the main window's showEvent:

void DeepSkyStacker::showEvent(QShowEvent* event)
{
	if (!event->spontaneous())
	{
		if (!initialised)
		{
			initialised = true;
			onInitialise();
		}
	}
	// Invoke base class showEvent()
	return Inherited::showEvent(event);
}

The onInitialise() code used to read like this:

void DeepSkyStacker::onInitialise()
{
	ZFUNCTRACE_RUNTIME();
	//
	// Force setting of blackPointToZero as initially false
	//
	Workspace{}.setValue("RawDDP/BlackPointTo0", false);

	//
	// Set the Docking Area Corner Configuration so that the
	// Explorer Bar takes the full left side docking area
	//
	setCorner(Qt::TopLeftCorner, Qt::LeftDockWidgetArea);
	setCorner(Qt::BottomLeftCorner, Qt::LeftDockWidgetArea);

	ZTRACE_RUNTIME("Creating Explorer Bar (Left Panel)");
	explorerBar = new ExplorerBar(this);
	addDockWidget(Qt::LeftDockWidgetArea, explorerBar);

	ZTRACE_RUNTIME("Creating pictureList");
	pictureList = new DSS::PictureList(this);
	addDockWidget(Qt::BottomDockWidgetArea, pictureList);

	ZTRACE_RUNTIME("Creating stackedWidget");
	stackedWidget = new QStackedWidget(this);
	stackedWidget->setObjectName("stackedWidget");
	setCentralWidget(stackedWidget);

	ZTRACE_RUNTIME("Creating Stacking Panel");
	stackingDlg = new DSS::StackingDlg(this, pictureList);
	stackingDlg->setObjectName("stackingDlg");

	ZTRACE_RUNTIME("Adding Stacking Panel to stackedWidget");
	stackedWidget->addWidget(stackingDlg);

	winHost = new QWinHost(stackedWidget);
	winHost->setObjectName("winHost");
	stackedWidget->addWidget(winHost);

	ZTRACE_RUNTIME("Creating Processing Panel");
	auto result = processingDlg->Create(IDD_PROCESSING);
	if (FALSE == result)
	{
		int lastErr = GetLastError();
		ZTRACE_RUNTIME("lastErr = %d", lastErr);	
	}
	processingDlg->setParent(winHost);			// Provide a Qt object to be parent for any Qt Widgets this creates

	HWND hwnd{ processingDlg->GetSafeHwnd() };
	Q_ASSERT(NULL != hwnd);
	winHost->setWindow(hwnd);
	:
	:
	//
	// Set initial size of the bottom dock widget (pictureList)
	//
	resizeDocks({ pictureList }, { 150 }, Qt::Vertical);

	ZTRACE_RUNTIME("Restoring Window State and Position");
	QSettings settings;
	settings.beginGroup("MainWindow");

	auto geometry{ settings.value("geometry", QByteArray()).toByteArray() };
	auto windowState{ settings.value("windowState", QByteArray()).toByteArray() };

#ifndef NDEBUG
	if (geometry.length())
	{
		ZTRACE_RUNTIME("Hex dump of geometry:");
		ZTrace::dumpHex(geometry.constData(), geometry.length());
	}
	if (windowState.length())
	{
		ZTRACE_RUNTIME("Hex dump of windowState:");
		ZTrace::dumpHex(windowState.constData(), windowState.length());
	}
#endif

	if (settings.value("maximised").toBool())
	{
		showMaximized();
		setGeometry(screen()->availableGeometry());
	}
	else restoreGeometry(geometry);

	restoreState(windowState);
	settings.endGroup();

That worked except the size of the dock widgets wasn't restored properly. In response to another topic https://forum.qt.io/topic/151253/preserving-restoring-qdockwidget-size, @Axel-Spoerl suggested I move the code for the creation and sizing of the dock widgets to the ctor which I did.

So the revised code in onInitialise() now reads:

void DeepSkyStacker::onInitialise()
{
	ZFUNCTRACE_RUNTIME();
	//
	// Force setting of blackPointToZero as initially false
	//
	Workspace{}.setValue("RawDDP/BlackPointTo0", false);

	ZTRACE_RUNTIME("Creating stackedWidget");
	stackedWidget = new QStackedWidget(this);
	stackedWidget->setObjectName("stackedWidget");
	setCentralWidget(stackedWidget);

	ZTRACE_RUNTIME("Creating Stacking Panel");
	stackingDlg = new DSS::StackingDlg(this, pictureList);
	stackingDlg->setObjectName("stackingDlg");

	ZTRACE_RUNTIME("Adding Stacking Panel to stackedWidget");
	stackedWidget->addWidget(stackingDlg);

	winHost = new QWinHost(stackedWidget);
	winHost->setObjectName("winHost");
	stackedWidget->addWidget(winHost);

	ZTRACE_RUNTIME("Creating Processing Panel");
	auto result = processingDlg->Create(IDD_PROCESSING);
	if (FALSE == result)
	{
		int lastErr = GetLastError();
		ZTRACE_RUNTIME("lastErr = %d", lastErr);	
	}
	processingDlg->setParent(winHost);			// Provide a Qt object to be parent for any Qt Widgets this creates

	HWND hwnd{ processingDlg->GetSafeHwnd() };
	Q_ASSERT(NULL != hwnd);
	winHost->setWindow(hwnd);

The call to processingDlg->Create() now fails with result of 0 (FALSE) and GetLastError returns 0!

Debugging into the MFC code finally lead me to the call:

hWnd = ::CreateDialogIndirect(hInst, lpDialogTemplate,
	pParentWnd != NULL ? 			pParentWnd != NULL ? pParentWnd->GetSafeHwnd() : NULL, AfxDlgProc);
#ifdef _DEBUG
		dwError = ::GetLastError();
#endif

in dlgcore.cpp at line 373 which was returning a NULL HWND with dwError being set to 0x57E (ERROR_TLW_WITH_WSCHILD). And indeed the rc file does say:

IDD_PROCESSING DIALOGEX 0, 0, 438, 332
STYLE DS_SETFONT | DS_FIXEDSYS | DS_CONTROL | WS_CHILD
FONT 8, "MS Shell Dlg", 0, 0, 0x0
BEGIN
    CONTROL         "",IDC_PICTURE,"Static",SS_BLACKFRAME | SS_SUNKEN,6,28,427,148
    LTEXT           "Histo",IDC_ORIGINAL_HISTOGRAM,177,186,256,140,SS_SUNKEN
    LTEXT           "Settings",IDC_SETTINGS,6,189,167,137,NOT WS_VISIBLE,WS_EX_STATICEDGE
    LTEXT           "",IDC_INFO,6,6,427,16,0,WS_EX_TRANSPARENT
    CONTROL         "",IDC_PROCESSING_PROGRESS,"msctls_progress32",PBS_SMOOTH,6,176,427,4
END

Why did it work before though???

[Perdrix]

Changing the dialogue definition changing WS_CHILD to WS_POPUP appears to fix it.

IDD_PROCESSING DIALOGEX 0, 0, 438, 332
STYLE DS_SETFONT | DS_FIXEDSYS | DS_CONTROL | WS_POPUP
FONT 8, "MS Shell Dlg", 0, 0, 0x0
BEGIN
    CONTROL         "",IDC_PICTURE,"Static",SS_BLACKFRAME | SS_SUNKEN,6,28,427,148
    LTEXT           "Histo",IDC_ORIGINAL_HISTOGRAM,177,186,256,140,SS_SUNKEN
    LTEXT           "Settings",IDC_SETTINGS,6,189,167,137,NOT WS_VISIBLE,WS_EX_STATICEDGE
    LTEXT           "",IDC_INFO,6,6,427,16,0,WS_EX_TRANSPARENT
    CONTROL         "",IDC_PROCESSING_PROGRESS,"msctls_progress32",PBS_SMOOTH,6,176,427,4
END

David