Don't create duplicate central frame with restoring

When using MainWindowOption_HasCentralFrame we have a persistent
central frame which is never destroyed. When restoring a layout
we shouldn't create it, as it exists already.

src/LayoutSaver.cpp

@@ -652,7 +652,7 @@ QVariantMap LayoutSaver::Frame::toVariantMap() const
     map.insert(QStringLiteral("geometry"), Layouting::rectToMap(geometry));
     map.insert(QStringLiteral("options"), options);
     map.insert(QStringLiteral("currentTabIndex"), currentTabIndex);
-
+    map.insert(QStringLiteral("mainWindowUniqueName"), mainWindowUniqueName);
     map.insert(QStringLiteral("dockWidgets"), dockWidgetNames(dockWidgets));
 
     return map;
@@ -669,6 +669,7 @@ void LayoutSaver::Frame::fromVariantMap(const QVariantMap &map)
     id = map.value(QStringLiteral("id")).toString();
     isNull = map.value(QStringLiteral("isNull")).toBool();
     objectName = map.value(QStringLiteral("objectName")).toString();
+    mainWindowUniqueName = map.value(QStringLiteral("mainWindowUniqueName")).toString();
     geometry = Layouting::mapToRect(map.value(QStringLiteral("geometry")).toMap());
     options = static_cast<QFlags<FrameOption>::Int>(map.value(QStringLiteral("options")).toUInt());
     currentTabIndex = map.value(QStringLiteral("currentTabIndex")).toInt();

src/private/DropAreaWithCentralFrame_p.h

@@ -28,6 +28,7 @@ public:
 
 private:
     friend class MainWindowBase;
+    friend class Frame;
     Frame *const m_centralFrame = nullptr;
 };
 

src/private/Frame.cpp

@@ -31,6 +31,7 @@
 #include "Utils_p.h"
 #include "WidgetResizeHandler_p.h"
 #include "MDILayoutWidget_p.h"
+#include "DropAreaWithCentralFrame_p.h"
 
 #include <QCloseEvent>
 #include <QTimer>
@@ -147,7 +148,8 @@ void Frame::insertWidget(DockWidgetBase *dockWidget, int index, InitialOption ad
 {
     Q_ASSERT(dockWidget);
     if (containsDockWidget(dockWidget)) {
-        qWarning() << "Frame::addWidget dockWidget already exists. this=" << this << "; dockWidget=" << dockWidget;
+        if (!dockWidget->isPersistentCentralDockWidget())
+            qWarning() << "Frame::addWidget dockWidget already exists. this=" << this << "; dockWidget=" << dockWidget;
         return;
     }
     if (m_layoutItem)
@@ -652,7 +654,37 @@ Frame *Frame::deserialize(const LayoutSaver::Frame &f)
     if (!f.isValid())
         return nullptr;
 
-    auto frame = Config::self().frameworkWidgetFactory()->createFrame(/*parent=*/nullptr, FrameOptions(f.options));
+    const FrameOptions options = FrameOptions(f.options);
+    Frame *frame = nullptr;
+    const bool isPersistentCentralFrame = options & FrameOption::FrameOption_IsCentralFrame;
+    auto widgetFactory = Config::self().frameworkWidgetFactory();
+
+    if (isPersistentCentralFrame) {
+        // Don't create a new Frame if we're restoring the Persistent Central frame (the one created
+        // by MainWindowOption_HasCentralFrame). It already exists.
+
+        if (f.mainWindowUniqueName.isEmpty()) {
+            // Can happen with older serialization formats
+            qWarning() << Q_FUNC_INFO << "Frame is the persistent central frame but doesn't have"
+                       << "an associated window name";
+        } else {
+            if (MainWindowBase *mw = DockRegistry::self()->mainWindowByName(f.mainWindowUniqueName)) {
+                frame = mw->dropArea()->m_centralFrame;
+                if (!frame) {
+                    // Doesn't happen...
+                    qWarning() << "Main window" << f.mainWindowUniqueName << "doesn't have central frame";
+                }
+            } else {
+                // Doesn't happen...
+                qWarning() << Q_FUNC_INFO << "Couldn't find main window"
+                           << f.mainWindowUniqueName;
+            }
+        }
+    }
+
+    if (!frame)
+        frame = widgetFactory->createFrame(/*parent=*/nullptr, options);
+
     frame->setObjectName(f.objectName);
 
     for (const auto &savedDock : qAsConst(f.dockWidgets)) {
@@ -680,6 +712,9 @@ LayoutSaver::Frame Frame::serialize() const
     frame.currentTabIndex = currentTabIndex();
     frame.id = id(); // for coorelation purposes
 
+    if (MainWindowBase *mw = mainWindow())
+        frame.mainWindowUniqueName = mw->uniqueName();
+
     for (DockWidgetBase *dock : docks)
         frame.dockWidgets.push_back(dock->d->serialize());
 

src/private/LayoutSaver_p.h

@@ -212,6 +212,10 @@ struct LayoutSaver::Frame
     int currentTabIndex;
     QString id; // for coorelation purposes
 
+    /// Might be empty if not in a main window. Used so we don't create a frame when restoring
+    /// the persistent central frame, that's never deleted when restoring
+    QString mainWindowUniqueName;
+
     LayoutSaver::DockWidget::List dockWidgets;
 };
 

tests/tst_docks.cpp

@@ -3746,6 +3746,23 @@ void TestDocks::tst_restoreSideBySide()
     }
 }
 
+void TestDocks::tst_restoreWithCentralFrameWithTabs()
+{
+    auto m = createMainWindow(QSize(500, 500), MainWindowOption_HasCentralFrame, "tst_restoreTwice");
+    auto dock1 = createDockWidget("1", new QPushButton("1"));
+    auto dock2 = createDockWidget("2", new QPushButton("2"));
+    m->addDockWidgetAsTab(dock1);
+    m->addDockWidgetAsTab(dock2);
+
+    QCOMPARE(DockRegistry::self()->frames().size(), 1);
+
+    LayoutSaver saver;
+    const QByteArray saved = saver.serializeLayout();
+    QVERIFY(saver.restoreLayout(saved));
+
+    QCOMPARE(DockRegistry::self()->frames().size(), 1);
+}
+
 void TestDocks::tst_restoreWithPlaceholder()
 {
     // Float dock1, save and restore, then unfloat and see if dock2 goes back to where it was

tests/tst_docks.h

@@ -106,6 +106,7 @@ private Q_SLOTS:
     void tst_restoreNestedAndTabbed();
     void tst_restoreCrash();
     void tst_restoreSideBySide();
+    void tst_restoreWithCentralFrameWithTabs();
     void tst_restoreWithPlaceholder();
     void tst_restoreWithAffinity();
     void tst_marginsAfterRestore();