Recreate DDupl adapters when an adapter's output has no handle

This happens under unclear circumstances when switching two screes beween extended and duplicated mode.
Contrary to the error description, it goes away only once the user switched back.

Author: psieg

Software/grab/DDuplGrabber.cpp

@@ -221,6 +221,11 @@ bool anyWidgetOnThisMonitor(HMONITOR monitor, const QList<GrabWidget *> &grabWid
 }
 
 QList< ScreenInfo > * DDuplGrabber::screensWithWidgets(QList< ScreenInfo > * result, const QList<GrabWidget *> &grabWidgets)
+{
+	return __screensWithWidgets(result, grabWidgets);
+}
+
+QList< ScreenInfo > * DDuplGrabber::__screensWithWidgets(QList< ScreenInfo > * result, const QList<GrabWidget *> &grabWidgets, bool noRecursion)
 {
 	result->clear();
 
@@ -237,6 +242,17 @@ QList< ScreenInfo > * DDuplGrabber::screensWithWidgets(QList< ScreenInfo > * res
 		{
 			DXGI_OUTPUT_DESC outputDesc;
 			output->GetDesc(&outputDesc);
+			if (outputDesc.Monitor == NULL) {
+				if (!noRecursion) {
+					qWarning() << Q_FUNC_INFO << "Found a monitor with NULL handle. Recreating adapters";
+					recreateAdapters();
+					return __screensWithWidgets(result, grabWidgets, true);
+				} else {
+					qWarning() << Q_FUNC_INFO << "Found a monitor with NULL handle (after recreation)";
+					continue;
+				}
+			}
+
 			if (anyWidgetOnThisMonitor(outputDesc.Monitor, grabWidgets))
 			{
 				ScreenInfo screenInfo;
@@ -357,6 +373,7 @@ bool DDuplGrabber::_reallocate(const QList< ScreenInfo > &grabScreens, bool noRe
 	}
 
 	BOOL success = SetThreadDesktop(screensaverDesk);
+	CloseHandle(screensaverDesk);
 	if (!success) {
 		qCritical(Q_FUNC_INFO " Failed to set grab desktop: %x", GetLastError());
 		return false;

Software/grab/GrabberBase.cpp

@@ -119,6 +119,11 @@ void GrabberBase::grab()
 	QList< ScreenInfo > screens2Grab;
 	screens2Grab.reserve(5);
 	screensWithWidgets(&screens2Grab, *_context->grabWidgets);
+	if (screens2Grab.empty()) {
+		qCritical() << Q_FUNC_INFO << "No screens with widgets found";
+		emit frameGrabAttempted(GrabResultError);
+		return;
+	}
 	if (isReallocationNeeded(screens2Grab)) {
 		DEBUG_LOW_LEVEL << Q_FUNC_INFO << "reallocating";
 		if (!reallocate(screens2Grab)) {

Software/grab/include/DDuplGrabber.hpp

@@ -74,9 +74,10 @@ public slots:
 protected slots:
 	virtual GrabResult grabScreens();
 	virtual bool reallocate(const QList< ScreenInfo > &grabScreens);
-	virtual bool _reallocate(const QList< ScreenInfo > &grabScreens, bool noRecursion = false);
+	bool _reallocate(const QList< ScreenInfo > &grabScreens, bool noRecursion = false);
 
 	virtual QList< ScreenInfo > * screensWithWidgets(QList< ScreenInfo > * result, const QList<GrabWidget *> &grabWidgets);
+	QList< ScreenInfo > * __screensWithWidgets(QList< ScreenInfo > * result, const QList<GrabWidget *> &grabWidgets, bool noRecursion = false);
 
 	virtual bool isReallocationNeeded(const QList< ScreenInfo > &grabScreens) const;