Fix handling of changes to the root index of a VisualDataModel.

Store the root index as a QPersistentModelIndex so the index remains
valid as the model changes, and in the case the root index is
removed from the model invalidate the contents of the VisualDataModel
until a new root index or model is set.

Change-Id: I1cbc27f2068f99a02ff3d43373905dec7e35e900
Reviewed-by: Martin Jones <martin.jones@nokia.com>

4 files changed, 49 insertions, 4 deletions

diff --git a/src/quick/items/qquickvisualadaptormodel.cpp b/src/quick/items/qquickvisualadaptormodel.cpp
index b17ab26373..5076d84b81 100644
--- a/src/quick/items/qquickvisualadaptormodel.cpp
+++ b/src/quick/items/qquickvisualadaptormodel.cpp
@@ -459,6 +459,8 @@ public:
         if (aim && vdm) {
             QObject::disconnect(aim, SIGNAL(rowsInserted(QModelIndex,int,int)),
                                 vdm, SLOT(_q_rowsInserted(QModelIndex,int,int)));
+            QObject::disconnect(aim, SIGNAL(rowsAboutToBeRemoved(QModelIndex,int,int)),
+                                vdm, SLOT(_q_rowsAboutToBeRemoved(QModelIndex,int,int)));
             QObject::disconnect(aim, SIGNAL(rowsRemoved(QModelIndex,int,int)),
                                 vdm, SLOT(_q_rowsRemoved(QModelIndex,int,int)));
             QObject::disconnect(aim, SIGNAL(dataChanged(QModelIndex,QModelIndex,QVector<int>)),
@@ -898,6 +900,8 @@ void QQuickVisualAdaptorModel::setModel(const QVariant &variant, QQuickVisualDat
                               vdm, QQuickVisualDataModel, SLOT(_q_rowsInserted(QModelIndex,int,int)));
             qmlobject_connect(model, QAbstractItemModel, SIGNAL(rowsRemoved(QModelIndex,int,int)),
                               vdm,  QQuickVisualDataModel, SLOT(_q_rowsRemoved(QModelIndex,int,int)));
+            qmlobject_connect(model, QAbstractItemModel, SIGNAL(rowsAboutToBeRemoved(QModelIndex,int,int)),
+                              vdm,  QQuickVisualDataModel, SLOT(_q_rowsAboutToBeRemoved(QModelIndex,int,int)));
             qmlobject_connect(model, QAbstractItemModel, SIGNAL(dataChanged(QModelIndex,QModelIndex,QVector<int>)),
                               vdm, QQuickVisualDataModel, SLOT(_q_dataChanged(QModelIndex,QModelIndex,QVector<int>)));
             qmlobject_connect(model, QAbstractItemModel, SIGNAL(rowsMoved(QModelIndex,int,int,QModelIndex,int)),
@@ -922,6 +926,19 @@ void QQuickVisualAdaptorModel::setModel(const QVariant &variant, QQuickVisualDat
     }
 }
 
+void QQuickVisualAdaptorModel::invalidateModel(QQuickVisualDataModel *vdm)
+{
+    accessors->cleanup(*this, vdm);
+    accessors = &qt_vdm_null_accessors;
+    // Don't clear the model object as we still need the guard to clear the list variant if the
+    // object is destroyed.
+}
+
+bool QQuickVisualAdaptorModel::isValid() const
+{
+    return accessors != &qt_vdm_null_accessors;
+}
+
 void QQuickVisualAdaptorModel::objectDestroyed(QObject *)
 {
     setModel(QVariant(), 0, 0);
diff --git a/src/quick/items/qquickvisualadaptormodel_p.h b/src/quick/items/qquickvisualadaptormodel_p.h
index d1b66a9963..ff42c4908d 100644
--- a/src/quick/items/qquickvisualadaptormodel_p.h
+++ b/src/quick/items/qquickvisualadaptormodel_p.h
@@ -96,7 +96,7 @@ public:
     };
 
     const Accessors *accessors;
-    QModelIndex rootIndex;
+    QPersistentModelIndex rootIndex;
     QQuickListAccessor list;
 
     QQuickVisualAdaptorModel();
@@ -104,6 +104,9 @@ public:
 
     inline QVariant model() const { return list.list(); }
     void setModel(const QVariant &variant, QQuickVisualDataModel *vdm, QQmlEngine *engine);
+    void invalidateModel(QQuickVisualDataModel *vdm);
+
+    bool isValid() const;
 
     inline QAbstractItemModel *aim() { return static_cast<QAbstractItemModel *>(object()); }
     inline const QAbstractItemModel *aim() const { return static_cast<const QAbstractItemModel *>(object()); }
diff --git a/src/quick/items/qquickvisualdatamodel.cpp b/src/quick/items/qquickvisualdatamodel.cpp
index 92cce3238e..2ce6ead7f3 100644
--- a/src/quick/items/qquickvisualdatamodel.cpp
+++ b/src/quick/items/qquickvisualdatamodel.cpp
@@ -391,7 +391,7 @@ void QQuickVisualDataModel::setDelegate(QQmlComponent *delegate)
 QVariant QQuickVisualDataModel::rootIndex() const
 {
     Q_D(const QQuickVisualDataModel);
-    return QVariant::fromValue(d->m_adaptorModel.rootIndex);
+    return QVariant::fromValue(QModelIndex(d->m_adaptorModel.rootIndex));
 }
 
 void QQuickVisualDataModel::setRootIndex(const QVariant &root)
@@ -399,9 +399,12 @@ void QQuickVisualDataModel::setRootIndex(const QVariant &root)
     Q_D(QQuickVisualDataModel);
 
     QModelIndex modelIndex = qvariant_cast<QModelIndex>(root);
-    if (d->m_adaptorModel.rootIndex != modelIndex) {
+    const bool changed = d->m_adaptorModel.rootIndex != modelIndex;
+    if (changed || !d->m_adaptorModel.isValid()) {
         const int oldCount = d->m_count;
         d->m_adaptorModel.rootIndex = modelIndex;
+        if (!d->m_adaptorModel.isValid() && d->m_adaptorModel.aim())  // The previous root index was invalidated, so we need to reconnect the model.
+            d->m_adaptorModel.setModel(d->m_adaptorModel.list.list(), this, d->m_context->engine());
         if (d->m_adaptorModel.canFetchMore())
             d->m_adaptorModel.fetchMore();
         if (d->m_complete) {
@@ -411,7 +414,8 @@ void QQuickVisualDataModel::setRootIndex(const QVariant &root)
             if (newCount)
                 _q_itemsInserted(0, newCount);
         }
-        emit rootIndexChanged();
+        if (changed)
+            emit rootIndexChanged();
     }
 }
 
@@ -1433,6 +1437,26 @@ void QQuickVisualDataModel::_q_rowsInserted(const QModelIndex &parent, int begin
         _q_itemsInserted(begin, end - begin + 1);
 }
 
+void QQuickVisualDataModel::_q_rowsAboutToBeRemoved(const QModelIndex &parent, int begin, int end)
+{
+    Q_D(QQuickVisualDataModel);
+    if (!d->m_adaptorModel.rootIndex.isValid())
+        return;
+    const QModelIndex index = d->m_adaptorModel.rootIndex;
+    if (index.parent() == parent && index.row() >= begin && index.row() <= end) {
+        const int oldCount = d->m_count;
+        d->m_count = 0;
+        d->m_adaptorModel.invalidateModel(this);
+
+        if (d->m_complete && oldCount > 0) {
+            QVector<Compositor::Remove> removes;
+            d->m_compositor.listItemsRemoved(&d->m_adaptorModel, 0, oldCount, &removes);
+            d->itemsRemoved(removes);
+            d->emitChanges();
+        }
+    }
+}
+
 void QQuickVisualDataModel::_q_rowsRemoved(const QModelIndex &parent, int begin, int end)
 {
     Q_D(QQuickVisualDataModel);
diff --git a/src/quick/items/qquickvisualdatamodel_p.h b/src/quick/items/qquickvisualdatamodel_p.h
index 1a8541f43c..8c52a2c9ef 100644
--- a/src/quick/items/qquickvisualdatamodel_p.h
+++ b/src/quick/items/qquickvisualdatamodel_p.h
@@ -137,6 +137,7 @@ private Q_SLOTS:
     void _q_itemsMoved(int from, int to, int count);
     void _q_modelReset();
     void _q_rowsInserted(const QModelIndex &,int,int);
+    void _q_rowsAboutToBeRemoved(const QModelIndex &parent, int begin, int end);
     void _q_rowsRemoved(const QModelIndex &,int,int);
     void _q_rowsMoved(const QModelIndex &, int, int, const QModelIndex &, int);
     void _q_dataChanged(const QModelIndex&,const QModelIndex&,const QVector<int> &);