QIdentityProxyModel: add setHandleSourceLayoutChanges(bool)

Some sub-classes have special handling of source model layout changes
(abbreviated as SMLC from here on out), they relied on disconnecting the
connections to the _q_*layout* slots in the private class using the SLOT
macro. This isn't possible any more after recent changes (and the method
were renamed to remove _q_ prefix).

Sub-classes resorting to using private API is a clear sign some
functionality is missing from the public API, so a cleaner solution for
this issue is adding this setter which enables sub-classes to tell
QIdentityProxyModel to leave handling of the SMLC to them. Thanks to
David Faure for the idea/solution.

[ChangeLog][QtCore][QIdentityProxyModel] Added
setHandleSourceLayoutChanges(bool) method to allow sub-classes to
indicate to QIdentityProxyModel that they will handle source model
layout changes on their own. Also added a getter,
isHandleSourceLayoutChanges().

Change-Id: I1de79dd693ce32a6e2df9a7c81dd4abdc5f00248
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

src/corelib/itemmodels/qidentityproxymodel.cpp

@@ -335,16 +335,52 @@ void QIdentityProxyModel::setSourceModel(QAbstractItemModel* newSourceModel)
                                     &QIdentityProxyModelPrivate::sourceDataChanged),
             QObjectPrivate::connect(m, &QAbstractItemModel::headerDataChanged, d,
                                     &QIdentityProxyModelPrivate::sourceHeaderDataChanged),
-            QObjectPrivate::connect(m, &QAbstractItemModel::layoutAboutToBeChanged, d,
-                                    &QIdentityProxyModelPrivate::sourceLayoutAboutToBeChanged),
-            QObjectPrivate::connect(m, &QAbstractItemModel::layoutChanged, d,
-                                    &QIdentityProxyModelPrivate::sourceLayoutChanged),
         };
+
+        if (d->m_handleLayoutChanges) {
+            d->m_sourceModelConnections.emplace_back(
+                QObjectPrivate::connect(m, &QAbstractItemModel::layoutAboutToBeChanged, d,
+                                        &QIdentityProxyModelPrivate::sourceLayoutAboutToBeChanged));
+            d->m_sourceModelConnections.emplace_back(
+                QObjectPrivate::connect(m, &QAbstractItemModel::layoutChanged, d,
+                                        &QIdentityProxyModelPrivate::sourceLayoutChanged));
+        }
     }
 
     endResetModel();
 }
 
+/*!
+    \since 6.7
+
+    If \a b is \c true, this proxy model will handle the source model layout
+    changes (by connecting to \c QAbstractItemModel::layoutAboutToBeChanged
+    and \c QAbstractItemModel::layoutChanged singals).
+
+    The default is for this proxy model to handle the source model layout
+    changes.
+
+    In sub-classes of QIdentityProxyModel, it may be useful to set this to
+    \c false if you need to specially handle the source model layout changes.
+
+    \note Calling this method will only have an effect after calling setSourceModel().
+*/
+void QIdentityProxyModel::setHandleSourceLayoutChanges(bool b)
+{
+    d_func()->m_handleLayoutChanges = b;
+}
+
+/*!
+    \since 6.7
+
+    Returns \c true if this proxy model handles the source model layout
+    changes, otherwise returns \c false.
+*/
+bool QIdentityProxyModel::isHandleSourceLayoutChanges() const
+{
+    return d_func()->m_handleLayoutChanges;
+}
+
 void QIdentityProxyModelPrivate::sourceColumnsAboutToBeInserted(const QModelIndex &parent, int start, int end)
 {
     Q_ASSERT(parent.isValid() ? parent.model() == model : true);

src/corelib/itemmodels/qidentityproxymodel.h

@@ -44,8 +44,11 @@ public:
     bool moveRows(const QModelIndex &sourceParent, int sourceRow, int count, const QModelIndex &destinationParent, int destinationChild) override;
     bool moveColumns(const QModelIndex &sourceParent, int sourceColumn, int count, const QModelIndex &destinationParent, int destinationChild) override;
 
+    bool isHandleSourceLayoutChanges() const;
+
 protected:
     QIdentityProxyModel(QIdentityProxyModelPrivate &dd, QObject* parent);
+    void setHandleSourceLayoutChanges(bool);
 
 private:
     Q_DECLARE_PRIVATE(QIdentityProxyModel)

src/corelib/itemmodels/qidentityproxymodel_p.h

@@ -63,6 +63,7 @@ public:
     void sourceModelReset();
 
 private:
+    bool m_handleLayoutChanges = true;
     QVarLengthArray<QMetaObject::Connection, 18> m_sourceModelConnections;
 };
 

tests/auto/corelib/itemmodels/qidentityproxymodel/tst_qidentityproxymodel.cpp

@@ -27,6 +27,16 @@ public:
         const QModelIndex idx = index(0, 0, QModelIndex());
         Q_EMIT dataChanged(idx, idx, QList<int>() << 1);
     }
+
+    // Workaround QObject::isSignalConnected() being a protected method
+    bool isConnected(const QMetaMethod &m) const { return isSignalConnected(m); }
+};
+
+class IdentityProxyModel : public QIdentityProxyModel
+{
+public:
+    // The name has to be different than the method from the base class
+    void setHandleSLC(bool b) { setHandleSourceLayoutChanges(b); }
 };
 
 class tst_QIdentityProxyModel : public QObject
@@ -53,6 +63,9 @@ private slots:
 
     void persistIndexOnLayoutChange();
     void createPersistentOnLayoutAboutToBeChanged();
+
+    void testSetHandleLayoutChanges();
+
 protected:
     void verifyIdentity(QAbstractItemModel *model, const QModelIndex &parent = QModelIndex());
 
@@ -513,5 +526,27 @@ void tst_QIdentityProxyModel::createPersistentOnLayoutAboutToBeChanged() // QTBU
     QCOMPARE(layoutChangedSpy.size(), 1);
 }
 
+void tst_QIdentityProxyModel::testSetHandleLayoutChanges()
+{
+    const std::array layoutSignals = {
+        QMetaMethod::fromSignal(&QAbstractItemModel::layoutChanged),
+        QMetaMethod::fromSignal(&QAbstractItemModel::layoutAboutToBeChanged),
+    };
+
+    DataChangedModel model;
+    IdentityProxyModel proxy;
+    proxy.setSourceModel(&model);
+    for (const auto &m : layoutSignals)
+        QVERIFY(model.isConnected(m)); // Connected by default
+
+    proxy.setSourceModel(nullptr);
+
+    // Disable handling (connecting to layotu signals) of source model layout changes
+    proxy.setHandleSLC(false);
+    proxy.setSourceModel(&model);
+    for (const auto &m : layoutSignals)
+        QVERIFY(!model.isConnected(m));
+}
+
 QTEST_MAIN(tst_QIdentityProxyModel)
 #include "tst_qidentityproxymodel.moc"