QAbstractProxyModel: fix canDropMimeData/dropMimeData implementations

The code in 4696e9dbaa4 was incorrect. It is perfectly valid to call
these methods with row=-1 column=1 parent=some_index, this is exactly
what happens in QListView and QTableView. Child row/column is only for
trees.

Move the coordinate mapping from QSortFilterProxyModel into a new
mapDropCoordinatesToSource internal method, used by QAbstractProxyModel.

Task-number: QTBUG-39549
Change-Id: I3312210473d84b639cbe4c01f70ea36437db3e91
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Stephen Kelly <steveire@gmail.com>

3 files changed, 34 insertions, 22 deletions

diff --git a/src/corelib/itemmodels/qabstractproxymodel.cpp b/src/corelib/itemmodels/qabstractproxymodel.cpp
index ce26293183..b7f988ef7c 100644
--- a/src/corelib/itemmodels/qabstractproxymodel.cpp
+++ b/src/corelib/itemmodels/qabstractproxymodel.cpp
@@ -384,6 +384,26 @@ QMimeData* QAbstractProxyModel::mimeData(const QModelIndexList &indexes) const
     return d->model->mimeData(list);
 }
 
+void QAbstractProxyModelPrivate::mapDropCoordinatesToSource(int row, int column, const QModelIndex &parent,
+                                                            int *sourceRow, int *sourceColumn, QModelIndex *sourceParent) const
+{
+    Q_Q(const QAbstractProxyModel);
+    *sourceRow = -1;
+    *sourceColumn = -1;
+    if (row == -1 && column == -1) {
+        *sourceParent = q->mapToSource(parent);
+    } else if (row == q->rowCount(parent)) {
+        *sourceParent = q->mapToSource(parent);
+        *sourceRow = model->rowCount(*sourceParent);
+    } else {
+        QModelIndex proxyIndex = q->index(row, column, parent);
+        QModelIndex sourceIndex = q->mapToSource(proxyIndex);
+        *sourceRow = sourceIndex.row();
+        *sourceColumn = sourceIndex.column();
+        *sourceParent = sourceIndex.parent();
+    }
+}
+
 /*!
     \reimp
     \since 5.4
@@ -392,8 +412,11 @@ bool QAbstractProxyModel::canDropMimeData(const QMimeData *data, Qt::DropAction
                                           int row, int column, const QModelIndex &parent) const
 {
     Q_D(const QAbstractProxyModel);
-    const QModelIndex source = mapToSource(index(row, column, parent));
-    return d->model->canDropMimeData(data, action, source.row(), source.column(), source.parent());
+    int sourceDestinationRow;
+    int sourceDestinationColumn;
+    QModelIndex sourceParent;
+    d->mapDropCoordinatesToSource(row, column, parent, &sourceDestinationRow, &sourceDestinationColumn, &sourceParent);
+    return d->model->canDropMimeData(data, action, sourceDestinationRow, sourceDestinationColumn, sourceParent);
 }
 
 /*!
@@ -404,8 +427,11 @@ bool QAbstractProxyModel::dropMimeData(const QMimeData *data, Qt::DropAction act
                                        int row, int column, const QModelIndex &parent)
 {
     Q_D(QAbstractProxyModel);
-    const QModelIndex source = mapToSource(index(row, column, parent));
-    return d->model->dropMimeData(data, action, source.row(), source.column(), source.parent());
+    int sourceDestinationRow;
+    int sourceDestinationColumn;
+    QModelIndex sourceParent;
+    d->mapDropCoordinatesToSource(row, column, parent, &sourceDestinationRow, &sourceDestinationColumn, &sourceParent);
+    return d->model->dropMimeData(data, action, sourceDestinationRow, sourceDestinationColumn, sourceParent);
 }
 
 /*!
diff --git a/src/corelib/itemmodels/qabstractproxymodel_p.h b/src/corelib/itemmodels/qabstractproxymodel_p.h
index 9402092fa8..24af5afc64 100644
--- a/src/corelib/itemmodels/qabstractproxymodel_p.h
+++ b/src/corelib/itemmodels/qabstractproxymodel_p.h
@@ -59,6 +59,8 @@ public:
     QAbstractProxyModelPrivate() : QAbstractItemModelPrivate(), model(0) {}
     QAbstractItemModel *model;
     virtual void _q_sourceModelDestroyed();
+    void mapDropCoordinatesToSource(int row, int column, const QModelIndex &parent,
+                                    int *source_row, int *source_column, QModelIndex *source_parent) const;
 };
 
 QT_END_NAMESPACE
diff --git a/src/corelib/itemmodels/qsortfilterproxymodel.cpp b/src/corelib/itemmodels/qsortfilterproxymodel.cpp
index 3c383532bb..0b2b0e4188 100644
--- a/src/corelib/itemmodels/qsortfilterproxymodel.cpp
+++ b/src/corelib/itemmodels/qsortfilterproxymodel.cpp
@@ -2030,30 +2030,14 @@ Qt::DropActions QSortFilterProxyModel::supportedDropActions() const
     return d->model->supportedDropActions();
 }
 
+// Qt6: remove unnecessary reimplementation
 /*!
   \reimp
 */
 bool QSortFilterProxyModel::dropMimeData(const QMimeData *data, Qt::DropAction action,
                                          int row, int column, const QModelIndex &parent)
 {
-    Q_D(QSortFilterProxyModel);
-    if ((row == -1) && (column == -1))
-        return d->model->dropMimeData(data, action, -1, -1, mapToSource(parent));
-    int source_destination_row = -1;
-    int source_destination_column = -1;
-    QModelIndex source_parent;
-    if (row == rowCount(parent)) {
-        source_parent = mapToSource(parent);
-        source_destination_row = d->model->rowCount(source_parent);
-    } else {
-        QModelIndex proxy_index = index(row, column, parent);
-        QModelIndex source_index = mapToSource(proxy_index);
-        source_destination_row = source_index.row();
-        source_destination_column = source_index.column();
-        source_parent = source_index.parent();
-    }
-    return d->model->dropMimeData(data, action, source_destination_row,
-                                  source_destination_column, source_parent);
+    return QAbstractProxyModel::dropMimeData(data, action, row, column, parent);
 }
 
 /*!