Provide the resetInternalData slot to cleanly reset data in proxy subclasses.

This was part of Qt 4.8, but Qt 5.0 was branched before that, so
the commit was lost.

Change-Id: I2a2ab3c75a0943ac734d588ebd74bc158dd6aaaf
Reviewed-by: Nils Jeisecke <jeisecke@saltation.de>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

src/corelib/doc/snippets/code/src_corelib_kernel_qabstractitemmodel.cpp

@@ -97,3 +97,37 @@ beginResetModel();
 myData.clear();
 endResetModel();
 //! [11]
+
+//! [12]
+class CustomDataProxy : public QSortFilterProxyModel
+{
+    Q_OBJECT
+public:
+    CustomDataProxy(QObject *parent)
+      : QSortFilterProxyModel(parent)
+    {
+    }
+
+    ...
+
+    QVariant data(const QModelIndex &index, int role)
+    {
+        if (role != Qt::BackgroundRole)
+            return QSortFilterProxyModel::data(index, role);
+
+        if (m_customData.contains(index.row()))
+            return m_customData.value(index.row());
+        return QSortFilterProxyModel::data(index, role);
+    }
+
+private slots:
+    void resetInternalData()
+    {
+        m_customData.clear();
+    }
+
+private:
+  QHash<int, QVariant> m_customData;
+};
+//! [12]
+

src/corelib/itemmodels/qabstractitemmodel.cpp

@@ -865,6 +865,27 @@ void QAbstractItemModelPrivate::columnsRemoved(const QModelIndex &parent,
     }
 }
 
+/*!
+    \since 4.8
+
+    This slot is called just after the internal data of a model is cleared
+    while it is being reset.
+
+    This slot is provided the convenience of subclasses of concrete proxy
+    models, such as subclasses of QSortFilterProxyModel which maintain extra
+    data.
+
+    \snippet code/src_corelib_kernel_qabstractitemmodel.cpp 12
+
+    \note Due to a mistake, this slot is missing in Qt 5.0.
+
+    \sa modelAboutToBeReset(), modelReset()
+*/
+void QAbstractItemModel::resetInternalData()
+{
+
+}
+
 /*!
     \class QModelIndex
     \inmodule QtCore
@@ -3055,6 +3076,7 @@ void QAbstractItemModel::endResetModel()
 {
     Q_D(QAbstractItemModel);
     d->invalidatePersistentIndexes();
+    QMetaObject::invokeMethod(this, "resetInternalData");
     emit modelReset(QPrivateSignal());
 }
 

src/corelib/itemmodels/qabstractitemmodel.h

@@ -330,6 +330,10 @@ public Q_SLOTS:
     virtual bool submit();
     virtual void revert();
 
+protected Q_SLOTS:
+    // Qt 6: Make virtual
+    void resetInternalData();
+
 protected:
     QAbstractItemModel(QAbstractItemModelPrivate &dd, QObject *parent = 0);
 

tests/auto/corelib/itemmodels/qsortfilterproxymodel/tst_qsortfilterproxymodel.cpp

@@ -136,6 +136,7 @@ private slots:
 
     void testMultipleProxiesWithSelection();
     void mapSelectionFromSource();
+    void testResetInternalData();
     void filteredColumns();
     void headerDataChanged();
 
@@ -3242,6 +3243,143 @@ void tst_QSortFilterProxyModel::resetInvalidate()
     QCOMPARE(ok, works);
 }
 
+/**
+ * A proxy which changes the background color for items ending in 'y' or 'r'
+ */
+class CustomDataProxy : public QSortFilterProxyModel
+{
+    Q_OBJECT
+
+public:
+    CustomDataProxy(QObject *parent = 0)
+        : QSortFilterProxyModel(parent)
+    {
+        setDynamicSortFilter(true);
+    }
+
+    void setSourceModel(QAbstractItemModel *sourceModel)
+    {
+        // It would be possible to use only the modelReset signal of the source model to clear
+        // the data in *this, however, this requires that the slot is connected
+        // before QSortFilterProxyModel::setSourceModel is called, and even then depends
+        // on the order of invocation of slots being the same as the order of connection.
+        // ie, not reliable.
+//         connect(sourceModel, SIGNAL(modelReset()), SLOT(resetInternalData()));
+        QSortFilterProxyModel::setSourceModel(sourceModel);
+        // Making the connect after the setSourceModel call clears the data too late.
+//         connect(sourceModel, SIGNAL(modelReset()), SLOT(resetInternalData()));
+
+        // This could be done in data(), but the point is to need to cache something in the proxy
+        // which needs to be cleared on reset.
+        for (int i = 0; i < sourceModel->rowCount(); ++i)
+        {
+            if (sourceModel->index(i, 0).data().toString().endsWith(QLatin1Char('y')))
+            {
+                m_backgroundColours.insert(i, Qt::blue);
+            } else if (sourceModel->index(i, 0).data().toString().endsWith(QLatin1Char('r')))
+            {
+                m_backgroundColours.insert(i, Qt::red);
+            }
+        }
+    }
+
+    QVariant data(const QModelIndex &index, int role) const
+    {
+        if (role != Qt::BackgroundRole)
+            return QSortFilterProxyModel::data(index, role);
+        return m_backgroundColours.value(index.row());
+    }
+
+private slots:
+  void resetInternalData()
+  {
+      m_backgroundColours.clear();
+  }
+
+private:
+    QHash<int, QColor> m_backgroundColours;
+};
+
+class ModelObserver : public QObject
+{
+    Q_OBJECT
+public:
+  ModelObserver(QAbstractItemModel *model, QObject *parent = 0)
+    : QObject(parent), m_model(model)
+  {
+    connect(m_model, SIGNAL(modelAboutToBeReset()), SLOT(modelAboutToBeReset()));
+    connect(m_model, SIGNAL(modelReset()), SLOT(modelReset()));
+  }
+
+public slots:
+  void modelAboutToBeReset()
+  {
+    int reds = 0, blues = 0;
+    for (int i = 0; i < m_model->rowCount(); ++i)
+    {
+      QColor color = m_model->index(i, 0).data(Qt::BackgroundRole).value<QColor>();
+      if (color == Qt::blue)
+        ++blues;
+      if (color == Qt::red)
+        ++reds;
+    }
+    QCOMPARE(blues, 11);
+    QCOMPARE(reds, 4);
+  }
+
+  void modelReset()
+  {
+    int reds = 0, blues = 0;
+    for (int i = 0; i < m_model->rowCount(); ++i)
+    {
+      QColor color = m_model->index(i, 0).data(Qt::BackgroundRole).value<QColor>();
+      if (color == Qt::blue)
+        ++blues;
+      if (color == Qt::red)
+        ++reds;
+    }
+    QCOMPARE(reds, 0);
+    QCOMPARE(blues, 0);
+  }
+
+private:
+  QAbstractItemModel * const m_model;
+
+};
+
+void tst_QSortFilterProxyModel::testResetInternalData()
+{
+
+    QStringListModel model(QStringList() << "Monday"
+                                         << "Tuesday"
+                                         << "Wednesday"
+                                         << "Thursday"
+                                         << "Friday"
+                                         << "January"
+                                         << "February"
+                                         << "March"
+                                         << "April"
+                                         << "May"
+                                         << "Saturday"
+                                         << "June"
+                                         << "Sunday"
+                                         << "July"
+                                         << "August"
+                                         << "September"
+                                         << "October"
+                                         << "November"
+                                         << "December");
+
+    CustomDataProxy proxy;
+    proxy.setSourceModel(&model);
+
+    ModelObserver observer(&proxy);
+
+    // Cause the source model to reset.
+    model.setStringList(QStringList() << "Spam" << "Eggs");
+
+}
+
 void tst_QSortFilterProxyModel::testParentLayoutChanged()
 {
     QStandardItemModel model;