Fixed case of corrupt layout when using setDockWidgetFactoryFunc()

If the factory returned null for some dock widget, then the layout
would have holes. They need to be turned into placeholders, which
will be invisible.

Move the test into the QtWidgets guard. There's no point in making
it agnostic, since the bug is in the layouting.

Author: iamsergio

src/LayoutSaver.cpp

@@ -411,8 +411,16 @@ void LayoutSaver::Private::deleteEmptyFrames()
     // Delete their frame now.
 
     for (auto frame : m_dockRegistry->frames()) {
-        if (!frame->beingDeletedLater() && frame->isEmpty() && !frame->isCentralFrame())
+        if (!frame->beingDeletedLater() && frame->isEmpty() && !frame->isCentralFrame()) {
+            if (auto item = frame->layoutItem()) {
+                item->turnIntoPlaceholder();
+            } else {
+                // This doesn't happen. But the warning will make the tests fail if there's a regression.
+                qWarning() << Q_FUNC_INFO << "Expected item for frame";
+            }
+
             delete frame;
+        }
     }
 }
 

src/private/multisplitter/Item_p.h

@@ -306,6 +306,7 @@ class DOCKS_EXPORT_FOR_UNIT_TESTS Item : public QObject
     void ref();
     void unref();
     int refCount() const;
+    void turnIntoPlaceholder();
 
     int minLength(Qt::Orientation) const;
     int maxLengthHint(Qt::Orientation) const;
@@ -374,7 +375,6 @@ private Q_SLOTS:
     friend class ItemContainer;
     friend class ItemBoxContainer;
     friend class ItemFreeContainer;
-    void turnIntoPlaceholder();
     bool eventFilter(QObject *o, QEvent *event) override;
     int m_refCount = 0;
     void updateObjectName();

tests/tst_docks.cpp

@@ -5720,6 +5720,28 @@ void TestDocks::tst_overlayCrash()
     pressOn(tb->mapToGlobal(QPoint(5, 5)), tb);
 }
 
+void TestDocks::tst_restoreWithIncompleteFactory()
+{
+    EnsureTopLevelsDeleted e;
+    SetExpectedWarning ignoreWarning("Couldn't find dock widget");
+    KDDockWidgets::Config::self().setDockWidgetFactoryFunc([](const QString &name) -> KDDockWidgets::DockWidgetBase * {
+        if (name.contains(QStringLiteral("centralDockWidget")))
+            return nullptr;
+
+        auto w = createDockWidget(name, new QPushButton("1"), {}, {}, false);
+        w->setWidget(new QWidget());
+        return w;
+    });
+
+    auto m = createMainWindow(QSize(500, 500), MainWindowOption_None, "MainWindow1");
+
+    LayoutSaver saver;
+    saver.restoreFromFile(":/layouts/restoreWithIncompleteFactory.json");
+
+    auto layout = m->multiSplitter();
+    QCOMPARE(layout->separators().size(), 0);
+}
+
 void TestDocks::tst_embeddedMainWindow()
 {
     EnsureTopLevelsDeleted e;
@@ -7933,26 +7955,3 @@ void TestDocks::tst_crash326()
     QEXPECT_FAIL("", "Bug #326, to be fixed", Continue);
     QVERIFY(originalFrame != dock1->d->frame());
 }
-
-void TestDocks::tst_restoreWithIncompleteFactory()
-{
-    EnsureTopLevelsDeleted e;
-    SetExpectedWarning ignoreWarning("Couldn't find dock widget");
-    KDDockWidgets::Config::self().setDockWidgetFactoryFunc([](const QString &name) -> KDDockWidgets::DockWidgetBase * {
-        if (name.contains(QStringLiteral("centralDockWidget")))
-            return nullptr;
-
-        auto w = new KDDockWidgets::DockWidget(name);
-        w->setWidget(new QWidget());
-        return w;
-    });
-
-    auto m = createMainWindow(QSize(500, 500), MainWindowOption_None, "MainWindow1");
-
-    LayoutSaver saver;
-    saver.restoreFromFile(":/layouts/restoreWithIncompleteFactory.json");
-
-    auto layout = m->multiSplitter();
-    QEXPECT_FAIL("", "To be fixed", Continue);
-    QCOMPARE(layout->separators().size(), 0);
-}

tests/tst_docks.h

@@ -248,7 +248,6 @@ private Q_SLOTS:
     void tst_persistentCentralWidget();
     void tst_setFloatingWindowFlags();
     void tst_crash326();
-    void tst_restoreWithIncompleteFactory();
 
 #ifdef KDDOCKWIDGETS_QTWIDGETS
     // TODO: Port these to QtQuick
@@ -276,6 +275,7 @@ private Q_SLOTS:
     void tst_floatRemovesFromSideBar();
     void tst_overlayedGeometryIsSaved();
     void tst_overlayCrash();
+    void tst_restoreWithIncompleteFactory();
 
     // And fix these
     void tst_floatingWindowDeleted();