Properly implemented save and restore with central widget

src/DockManager.cpp

@@ -279,6 +279,24 @@ bool DockManagerPrivate::restoreStateFromXml(const QByteArray &state,  int versi
     int  DockContainers = s.attributes().value("Containers").toInt();
 #endif
     ADS_PRINT(DockContainers);
+
+    const auto CentralWidgetAttribute = s.attributes().value("CentralWidget");
+    // If we have a central widget but a state without central widget, then
+    // something is wrong.
+	if (CentralWidget && CentralWidgetAttribute.isEmpty())
+	{
+		qWarning() << "Dock manager has central widget but saved state does not have central widget.";
+		return false;
+	}
+
+	// If the object name of the central widget does not match the name of the
+	// saved central widget, the something is wrong
+	if (CentralWidget->objectName() != CentralWidgetAttribute.toString())
+	{
+		qWarning() << "Object name of central widget does not match name of central widget in saved state.";
+		return false;
+	}
+
     int DockContainerCount = 0;
     while (s.readNextStartElement())
     {
@@ -405,7 +423,6 @@ bool DockManagerPrivate::restoreState(const QByteArray& State, int version)
     	return false;
     }
 
-    CentralWidget = nullptr;
     // Hide updates of floating widgets from use
     hideFloatingWidgets();
     markDockWidgetsDirty();
@@ -419,6 +436,7 @@ bool DockManagerPrivate::restoreState(const QByteArray& State, int version)
     restoreDockWidgetsOpenState();
     restoreDockAreasIndices();
     emitTopLevelEvents();
+    _this->dumpLayout();
 
     return true;
 }
@@ -636,6 +654,10 @@ QByteArray CDockManager::saveState(int version) const
 		s.writeAttribute("Version", QString::number(CurrentVersion));
 		s.writeAttribute("UserVersion", QString::number(version));
 		s.writeAttribute("Containers", QString::number(d->Containers.count()));
+		if (d->CentralWidget)
+		{
+			s.writeAttribute("CentralWidget", d->CentralWidget->objectName());
+		}
 		for (auto Container : d->Containers)
 		{
 			Container->saveState(s);
@@ -904,10 +926,20 @@ CDockAreaWidget* CDockManager::setCentralWidget(CDockWidget* widget)
 		return nullptr;
 	}
 
-	// Setting a new central widget is now allowed if there is alread a central
+	// Setting a new central widget is now allowed if there is already a central
-	// widget
+	// widget or if there are already other dock widgets
 	if (d->CentralWidget)
 	{
+		qWarning("Setting a central widget not possible because there is already a central widget.");
+		return nullptr;
+	}
+
+	// Setting a central widget is now allowed if there are already other
+	// dock widgets.
+	if (!d->DockWidgetsMap.isEmpty())
+	{
+		qWarning("Setting a central widget not possible - the central widget need to be the first "
+			"dock widget that is added to the dock manager.");
 		return nullptr;
 	}
 

src/DockManager.h

@@ -398,9 +398,12 @@ public:
      * movable, floatable or closable and the titlebar of the central
      * dock area is not visible.
      * If the given widget could be set as central widget, the function returns
-     * the created cok area. If the widget could not be set, because there
+     * the created dock area. If the widget could not be set, because there
      * is already a central widget, this function returns a nullptr.
      * To clear the central widget, pass a nullptr to the function.
+     * \note Setting a central widget is only possible if no other dock widgets
+     * have been registered before. That means, this function should be the
+     * first function that you call before you add other dock widgets.
      * \retval != 0 The dock area that contains the central widget
      * \retval nullptr Indicates that the given widget can not be set as central
      *         widget because there is already a central widget.