Improve safety in code (#588)

Delete areas later so that that they can be accessed by
(inherited) dock widgets in dtor. Add some QPointer to
prevent crashes.

Hence allow users to do more while dock widgets etc
are being destroyed.

src/DockAreaWidget.cpp

@@ -756,7 +756,7 @@ int CDockAreaWidget::openDockWidgetsCount() const
 	int Count = 0;
 	for (int i = 0; i < d->ContentsLayout->count(); ++i)
 	{
-		if (!dockWidget(i)->isClosed())
+		if (dockWidget(i) && !dockWidget(i)->isClosed())
 		{
 			++Count;
 		}
@@ -772,7 +772,7 @@ QList<CDockWidget*> CDockAreaWidget::openedDockWidgets() const
 	for (int i = 0; i < d->ContentsLayout->count(); ++i)
 	{
 		CDockWidget* DockWidget = dockWidget(i);
-		if (!DockWidget->isClosed())
+		if (DockWidget && !DockWidget->isClosed())
 		{
 			DockWidgetList.append(dockWidget(i));
 		}
@@ -786,7 +786,7 @@ int CDockAreaWidget::indexOfFirstOpenDockWidget() const
 {
 	for (int i = 0; i < d->ContentsLayout->count(); ++i)
 	{
-		if (!dockWidget(i)->isClosed())
+		if (dockWidget(i) && !dockWidget(i)->isClosed())
 		{
 			return i;
 		}
@@ -809,7 +809,6 @@ CDockWidget* CDockAreaWidget::dockWidget(int Index) const
 	return qobject_cast<CDockWidget*>(d->ContentsLayout->widget(Index));
 }
 
-
 //============================================================================
 void CDockAreaWidget::reorderDockWidget(int fromIndex, int toIndex)
 {

src/DockContainerWidget.cpp

@@ -141,7 +141,7 @@ class DockContainerWidgetPrivate
 	CDockContainerWidget* _this;
 	QPointer<CDockManager> DockManager;
 	unsigned int zOrderIndex = 0;
-	QList<CDockAreaWidget*> DockAreas;
+	QList<QPointer<CDockAreaWidget>> DockAreas;
 	QList<CAutoHideDockContainer*> AutoHideWidgets;
 	QMap<SideBarLocation, CAutoHideSideBar*> SideTabBarWidgets;
 	QGridLayout* Layout = nullptr;
@@ -299,7 +299,11 @@ class DockContainerWidgetPrivate
 		VisibleDockAreaCount = 0;
 		for (auto DockArea : DockAreas)
 		{
-			VisibleDockAreaCount += DockArea->isHidden() ? 0 : 1;
+			if (!DockArea)
+			{
+				continue;
+			}
+			VisibleDockAreaCount += (DockArea->isHidden() ? 0 : 1);
 		}
 	}
 
@@ -924,7 +928,10 @@ void DockContainerWidgetPrivate::addDockAreasToList(const QList<CDockAreaWidget*
 //============================================================================
 void DockContainerWidgetPrivate::appendDockAreas(const QList<CDockAreaWidget*> NewDockAreas)
 {
-	DockAreas.append(NewDockAreas);
+	for (auto *newDockArea : NewDockAreas)
+	{
+		DockAreas.append(newDockArea);
+	}
 	for (auto DockArea : NewDockAreas)
 	{
 		QObject::connect(DockArea,
@@ -1641,7 +1648,7 @@ CDockAreaWidget* CDockContainerWidget::dockAreaAt(const QPoint& GlobalPos) const
 {
 	for (const auto& DockArea : d->DockAreas)
 	{
-		if (DockArea->isVisible() && DockArea->rect().contains(DockArea->mapFromGlobal(GlobalPos)))
+		if (DockArea && DockArea->isVisible() && DockArea->rect().contains(DockArea->mapFromGlobal(GlobalPos)))
 		{
 			return DockArea;
 		}
@@ -1678,7 +1685,7 @@ int CDockContainerWidget::visibleDockAreaCount() const
 	int Result = 0;
 	for (auto DockArea : d->DockAreas)
 	{
-		Result += DockArea->isHidden() ? 0 : 1;
+		Result += (!DockArea || DockArea->isHidden()) ? 0 : 1;
 	}
 
 	return Result;
@@ -1802,7 +1809,7 @@ QList<CDockAreaWidget*> CDockContainerWidget::openedDockAreas() const
 	QList<CDockAreaWidget*> Result;
 	for (auto DockArea : d->DockAreas)
 	{
-		if (!DockArea->isHidden())
+		if (DockArea && !DockArea->isHidden())
 		{
 			Result.append(DockArea);
 		}
@@ -1818,7 +1825,7 @@ QList<CDockWidget*> CDockContainerWidget::openedDockWidgets() const
 	QList<CDockWidget*> DockWidgetList;
 	for (auto DockArea : d->DockAreas)
 	{
-		if (!DockArea->isHidden())
+		if (DockArea && !DockArea->isHidden())
 		{
 			DockWidgetList.append(DockArea->openedDockWidgets());
 		}
@@ -1833,7 +1840,7 @@ bool CDockContainerWidget::hasOpenDockAreas() const
 {
 	for (auto DockArea : d->DockAreas)
 	{
-		if (!DockArea->isHidden())
+		if (DockArea && !DockArea->isHidden())
 		{
 			return true;
 		}
@@ -2058,6 +2065,10 @@ QList<CDockWidget*> CDockContainerWidget::dockWidgets() const
 	QList<CDockWidget*> Result;
 	for (const auto DockArea : d->DockAreas)
 	{
+		if (!DockArea)
+		{
+			continue;
+		}
 		Result.append(DockArea->dockWidgets());
 	}
 
@@ -2090,6 +2101,10 @@ CDockWidget::DockWidgetFeatures CDockContainerWidget::features() const
 	CDockWidget::DockWidgetFeatures Features(CDockWidget::AllDockWidgetFeatures);
 	for (const auto DockArea : d->DockAreas)
 	{
+		if (!DockArea)
+		{
+			continue;
+		}
 		Features &= DockArea->features();
 	}
 
@@ -2109,7 +2124,7 @@ void CDockContainerWidget::closeOtherAreas(CDockAreaWidget* KeepOpenArea)
 {
 	for (const auto DockArea : d->DockAreas)
 	{
-		if (DockArea == KeepOpenArea)
+		if (!DockArea || DockArea == KeepOpenArea)
 		{
 			continue;
 		}

src/DockFocusController.cpp

@@ -115,6 +115,7 @@ DockFocusControllerPrivate::DockFocusControllerPrivate(
 //============================================================================
 void DockFocusControllerPrivate::updateDockWidgetFocus(CDockWidget* DockWidget)
 {
+	if (!DockWidget) return;
 	if (!DockWidget->features().testFlag(CDockWidget::DockWidgetFocusable))
 	{
 		return;

src/DockManager.cpp

@@ -103,8 +103,8 @@ static QString FloatingContainersTitle;
 struct DockManagerPrivate
 {
 	CDockManager* _this;
-	QList<CFloatingDockContainer*> FloatingWidgets;
-	QList<CFloatingDockContainer*> HiddenFloatingWidgets;
+	QList<QPointer<CFloatingDockContainer>> FloatingWidgets;
+	QList<QPointer<CFloatingDockContainer>> HiddenFloatingWidgets;
 	QList<CDockContainerWidget*> Containers;
 	CDockOverlay* ContainerOverlay;
 	CDockOverlay* DockAreaOverlay;
@@ -153,7 +153,10 @@ struct DockManagerPrivate
 		// Hide updates of floating widgets from user
 		for (auto FloatingWidget : FloatingWidgets)
 		{
-			FloatingWidget->hide();
+			if (FloatingWidget)
+			{
+			  FloatingWidget->hide();
+			}
 		}
 	}
 
@@ -333,7 +336,8 @@ bool DockManagerPrivate::restoreStateFromXml(const QByteArray &state,  int versi
 		int FloatingWidgetIndex = DockContainerCount - 1;
 		for (int i = FloatingWidgetIndex; i < FloatingWidgets.count(); ++i)
 		{
-			auto* floatingWidget = FloatingWidgets[i];
+			CFloatingDockContainer* floatingWidget = FloatingWidgets[i];
+			if (!floatingWidget) continue;
 			_this->removeDockContainer(floatingWidget->dockContainer());
 			floatingWidget->deleteLater();
 		}
@@ -536,32 +540,40 @@ CDockManager::CDockManager(QWidget *parent) :
 CDockManager::~CDockManager()
 {
     // fix memory leaks, see https://github.com/githubuser0xFFFF/Qt-Advanced-Docking-System/issues/307
-    std::vector<ads::CDockAreaWidget*> areas;
-    for ( int i = 0; i != dockAreaCount(); ++i )
-    {
-        auto area = dockArea(i);
-        if ( area->dockManager() == this )
-            areas.push_back( area );
-        // else, this is surprising, looks like this CDockAreaWidget is child of two different CDockManager
-        // this is reproductible by https://github.com/githubuser0xFFFF/Qt-Advanced-Docking-System/issues/585 testcase
-        // then, when a CDockManager deletes itself, it deletes the CDockAreaWidget, then, the other
-        // CDockManager will try to delete the CDockAreaWidget again and this will crash
-        // So let's just delete CDockAreaWidget we are the parent of!
-    }
-    for ( auto area : areas )
-    {
-        for ( auto widget : area->dockWidgets() )
-            delete widget;
+	std::vector<QPointer<ads::CDockAreaWidget>> areas;
+	for (int i = 0; i != dockAreaCount(); ++i)
+	{
+		areas.push_back( dockArea(i) );
+	}
+	for ( auto area : areas )
+	{
+		if (!area || area->dockManager() != this) continue;
 
-        delete area;
-    }
+		// QPointer delete safety - just in case some dock wigdet in destruction
+		// deletes another related/twin or child dock widget.
+		std::vector<QPointer<QWidget>> deleteWidgets;
+		for ( auto widget : area->dockWidgets() )
+		{
+			deleteWidgets.push_back(widget);
+		}
+		for ( auto ptrWdg : deleteWidgets)
+		{
+			delete ptrWdg;
+		}
+	}
 
 	auto FloatingWidgets = d->FloatingWidgets;
 	for (auto FloatingWidget : FloatingWidgets)
 	{
 		delete FloatingWidget;
 	}
 
+	// Delete Dock Widgets before Areas so widgets can access them late (like dtor)
+	for ( auto area : areas )
+	{
+		delete area;
+	}
+
 	delete d;
 }
 
@@ -732,7 +744,12 @@ const QList<CDockContainerWidget*> CDockManager::dockContainers() const
 //============================================================================
 const QList<CFloatingDockContainer*> CDockManager::floatingWidgets() const
 {
-	return d->FloatingWidgets;
+	QList<CFloatingDockContainer*> res;
+	for (auto &fl : d->FloatingWidgets)
+	{
+		if (fl) res.append(fl);
+	}
+	return res;
 }
 
 

src/DockWidget.cpp

@@ -81,7 +81,7 @@ struct DockWidgetPrivate
 	CDockWidgetTab* TabWidget = nullptr;
 	CDockWidget::DockWidgetFeatures Features = CDockWidget::DefaultDockWidgetFeatures;
 	CDockManager* DockManager = nullptr;
-	CDockAreaWidget* DockArea = nullptr;
+	QPointer<CDockAreaWidget> DockArea;
 	QAction* ToggleViewAction = nullptr;
 	bool Closed = false;
 	QScrollArea* ScrollArea = nullptr;