Item widgets: make indexFromItem const-correct

The item is not supposed to be modified, so it should be passed
as pointer-to-const. A similar change was already done for
QTreeWidget in b2aeeaf628.

Change-Id: I75d597867771f414821693a50f97c94b05a4ccb2
Reviewed-by: David Faure <david.faure@kdab.com>

src/widgets/itemviews/qlistwidget.cpp

@@ -189,8 +189,9 @@ int QListModel::rowCount(const QModelIndex &parent) const
     return parent.isValid() ? 0 : items.count();
 }
 
-QModelIndex QListModel::index(QListWidgetItem *item) const
+QModelIndex QListModel::index(const QListWidgetItem *item_) const
 {
+    QListWidgetItem *item = const_cast<QListWidgetItem *>(item_);
     if (!item || !item->view || static_cast<const QListModel *>(item->view->model()) != this
         || items.isEmpty())
         return QModelIndex();
@@ -1942,14 +1943,28 @@ QList<QListWidgetItem*> QListWidget::items(const QMimeData *data) const
 
 /*!
     Returns the QModelIndex associated with the given \a item.
+
+    \note In Qt versions prior to 5.10, this function took a non-\c{const} \a item.
 */
 
-QModelIndex QListWidget::indexFromItem(QListWidgetItem *item) const
+QModelIndex QListWidget::indexFromItem(const QListWidgetItem *item) const
 {
     Q_D(const QListWidget);
     return d->listModel()->index(item);
 }
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+/*!
+    \internal
+    \obsolete
+    \overload
+*/
+QModelIndex QListWidget::indexFromItem(QListWidgetItem *item) const
+{
+    return indexFromItem(const_cast<const QListWidgetItem *>(item));
+}
+#endif
+
 /*!
     Returns a pointer to the QListWidgetItem associated with the given \a index.
 */

src/widgets/itemviews/qlistwidget.h

@@ -297,7 +297,10 @@ protected:
 #endif
     QList<QListWidgetItem*> items(const QMimeData *data) const;
 
-    QModelIndex indexFromItem(QListWidgetItem *item) const;
+    QModelIndex indexFromItem(const QListWidgetItem *item) const;
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+    QModelIndex indexFromItem(QListWidgetItem *item) const; // ### Qt 6: remove
+#endif
     QListWidgetItem *itemFromIndex(const QModelIndex &index) const;
 
 private:

src/widgets/itemviews/qlistwidget_p.h

@@ -95,7 +95,7 @@ public:
 
     int rowCount(const QModelIndex &parent = QModelIndex()) const override;
 
-    QModelIndex index(QListWidgetItem *item) const;
+    QModelIndex index(const QListWidgetItem *item) const;
     QModelIndex index(int row, int column = 0, const QModelIndex &parent = QModelIndex()) const override;
 
     QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;

src/widgets/itemviews/qtablewidget.cpp

@@ -2652,14 +2652,28 @@ QList<QTableWidgetItem*> QTableWidget::items(const QMimeData *data) const
 
 /*!
   Returns the QModelIndex associated with the given \a item.
+
+  \note In Qt versions prior to 5.10, this function took a non-\c{const} \a item.
 */
 
-QModelIndex QTableWidget::indexFromItem(QTableWidgetItem *item) const
+QModelIndex QTableWidget::indexFromItem(const QTableWidgetItem *item) const
 {
     Q_D(const QTableWidget);
     return d->tableModel()->index(item);
 }
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+/*!
+  \internal
+  \obsolete
+  \overload
+*/
+QModelIndex QTableWidget::indexFromItem(QTableWidgetItem *item) const
+{
+    return indexFromItem(const_cast<const QTableWidgetItem *>(item));
+}
+#endif
+
 /*!
   Returns a pointer to the QTableWidgetItem associated with the given \a index.
 */

src/widgets/itemviews/qtablewidget.h

@@ -335,7 +335,10 @@ protected:
 #endif
     QList<QTableWidgetItem*> items(const QMimeData *data) const;
 
-    QModelIndex indexFromItem(QTableWidgetItem *item) const;
+    QModelIndex indexFromItem(const QTableWidgetItem *item) const;
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+    QModelIndex indexFromItem(QTableWidgetItem *item) const; // ### Qt 6: remove
+#endif
     QTableWidgetItem *itemFromIndex(const QModelIndex &index) const;
 
 protected:

src/widgets/itemviews/qtreewidget.cpp

@@ -3366,6 +3366,7 @@ QModelIndex QTreeWidget::indexFromItem(const QTreeWidgetItem *item, int column)
     return d->index(item, column);
 }
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 /*!
     \overload
     \internal
@@ -3374,6 +3375,7 @@ QModelIndex QTreeWidget::indexFromItem(QTreeWidgetItem *item, int column) const
 {
     return indexFromItem(const_cast<const QTreeWidgetItem *>(item), column);
 }
+#endif
 
 /*!
     Returns a pointer to the QTreeWidgetItem associated with the given \a index.

src/widgets/itemviews/qtreewidget.h

@@ -365,7 +365,9 @@ protected:
     QList<QTreeWidgetItem*> items(const QMimeData *data) const;
 
     QModelIndex indexFromItem(const QTreeWidgetItem *item, int column = 0) const;
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     QModelIndex indexFromItem(QTreeWidgetItem *item, int column = 0) const; // ### Qt 6: remove
+#endif
     QTreeWidgetItem *itemFromIndex(const QModelIndex &index) const;
 
 protected: