QGIM: override sibling() to avoid the roundtrip through parent()

Change-Id: I91bc8d3e94d35fb30bc4886ba6be554ca7cf866b
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>

src/corelib/itemmodels/qgenericitemmodel.cpp

@@ -448,6 +448,22 @@ QModelIndex QGenericItemModel::parent(const QModelIndex &child) const
     return impl->callConst<QModelIndex>(QGenericItemModelImplBase::Parent, child);
 }
 
+/*!
+    \reimp
+
+    Returns the sibling at \a row and \a column for the item at \a index, or an
+    invalid QModelIndex if there is no sibling at that location.
+
+    This implementation is significantly faster than going through the parent()
+    of the \a index.
+
+    \sa index(), QModelIndex::row(), QModelIndex::column()
+*/
+QModelIndex QGenericItemModel::sibling(int row, int column, const QModelIndex &index) const
+{
+    return impl->callConst<QModelIndex>(QGenericItemModelImplBase::Sibling, row, column, index);
+}
+
 /*!
     \reimp
 

src/corelib/itemmodels/qgenericitemmodel.h

@@ -58,6 +58,7 @@ public:
 
     QModelIndex index(int row, int column, const QModelIndex &parent = {}) const override;
     QModelIndex parent(const QModelIndex &child) const override;
+    QModelIndex sibling(int row, int column, const QModelIndex &index) const override;
     int rowCount(const QModelIndex &parent = {}) const override;
     int columnCount(const QModelIndex &parent = {}) const override;
     Qt::ItemFlags flags(const QModelIndex &index) const override;
@@ -210,6 +211,8 @@ public:
             break;
         case Parent: makeCall(that, &Structure::parent, r, args);
             break;
+        case Sibling: makeCall(that, &Self::sibling, r, args);
+            break;
         case RowCount: makeCall(that, &Structure::rowCount, r, args);
             break;
         case ColumnCount: makeCall(that, &Structure::columnCount, r, args);
@@ -258,6 +261,24 @@ public:
         return that().indexImpl(row, column, parent);
     }
 
+    QModelIndex sibling(int row, int column, const QModelIndex &index) const
+    {
+        if (row == index.row() && column == index.column())
+            return index;
+
+        if (column < 0 || column >= m_itemModel->columnCount())
+            return {};
+
+        if (row == index.row())
+            return createIndex(row, column, index.constInternalPointer());
+
+        const_row_ptr parentRow = static_cast<const_row_ptr>(index.constInternalPointer());
+        const auto siblingCount = size(that().childrenOf(parentRow));
+        if (row < 0 || row >= int(siblingCount))
+            return {};
+        return createIndex(row, column, parentRow);
+    }
+
     Qt::ItemFlags flags(const QModelIndex &index) const
     {
         if (!index.isValid())
@@ -1199,7 +1220,6 @@ protected:
         return std::addressof(*children);
     }
 
-private:
     const range_type &childrenOf(const_row_ptr row) const
     {
         if (!row)
@@ -1210,6 +1230,7 @@ private:
             return *m_protocol.childRows(*row);
     }
 
+private:
     range_type &childrenOf(row_ptr row)
     {
         if (!row)
@@ -1232,6 +1253,7 @@ class QGenericTableItemModelImpl
     using range_type = typename Base::range_type;
     using range_features = typename Base::range_features;
     using row_type = typename Base::row_type;
+    using const_row_ptr = typename Base::const_row_ptr;
     using row_traits = typename Base::row_traits;
     using row_features = typename Base::row_features;
 
@@ -1350,6 +1372,12 @@ protected:
         return nullptr;
     }
 
+    const range_type &childrenOf(const_row_ptr row) const
+    {
+        Q_ASSERT(!row);
+        return *this->m_data.model();
+    }
+
     void resetParentInChildren(range_type *)
     {
     }

src/corelib/itemmodels/qgenericitemmodel_impl.h

@@ -458,6 +458,7 @@ public:
     enum ConstOp {
         Index,
         Parent,
+        Sibling,
         RowCount,
         ColumnCount,
         Flags,

tests/auto/corelib/itemmodels/qgenericitemmodel/tst_qgenericitemmodel.cpp

@@ -292,6 +292,8 @@ private slots:
 
     void dimensions_data() { createTestData(); }
     void dimensions();
+    void sibling_data() { createTestData(); }
+    void sibling();
     void flags_data() { createTestData(); }
     void flags();
     void data_data() { createTestData(); }
@@ -892,6 +894,31 @@ void tst_QGenericItemModel::dimensions()
     QCOMPARE(model->columnCount(), expectedColumnCount);
 }
 
+void tst_QGenericItemModel::sibling()
+{
+    QFETCH(Factory, factory);
+    auto model = factory();
+
+    QModelIndex withChildren;
+    const auto test = [model = model.get(), &withChildren](const QModelIndex &parent){
+        const QModelIndex first = model->index(0, 0, parent);
+        // deliberately requesting siblings outside of the range
+        for (int r = 0; r < model->rowCount() + 1; ++r) {
+            for (int c = 0; c < model->columnCount() + 1; ++c) {
+                const QModelIndex next = model->sibling(r, c, first);
+                const QModelIndex qaimNext = model->QAbstractItemModel::sibling(r, c, first);
+                if (!withChildren.isValid() && model->hasChildren(next))
+                    withChildren = next;
+                QCOMPARE(next, qaimNext);
+            }
+        }
+    };
+
+    test({});
+    if (withChildren.isValid())
+        test(withChildren);
+}
+
 void tst_QGenericItemModel::flags()
 {
     QFETCH(Factory, factory);