QAbstractItemView: call canDropMimeData, as one would expect.

The virtual method was added for 5.0 but never called.

The old code (only checking mimetypes) is now the default implementation
for canDropMimeData. Model subclasses can now refine this by having
index-specific logic instead, or in order to inspect the dropped data
(e.g. to accept files and refuse directories, which are all text/uri-list).

[ChangeLog][QtWidgets][QAbstractItemView] now calls canDropMimeData in
order to decide whether or not to accept the drop.

Task-number: QTBUG-30534
Change-Id: Ied3aa964b4025bae6a1a26df89a681bfe61c3faa
Reviewed-by: Stephen Kelly <steveire@gmail.com>

6 files changed, 25 insertions, 6 deletions

diff --git a/src/widgets/doc/snippets/qlistview-dnd/main.cpp b/src/widgets/doc/snippets/qlistview-dnd/main.cpp
index c4a8aebb01..422ce35c6b 100644
--- a/src/widgets/doc/snippets/qlistview-dnd/main.cpp
+++ b/src/widgets/doc/snippets/qlistview-dnd/main.cpp
@@ -38,7 +38,7 @@
 **
 ****************************************************************************/
 
-#include <QtGui>
+#include <QtWidgets>
 
 #include "mainwindow.h"
 
diff --git a/src/widgets/doc/snippets/qlistview-dnd/mainwindow.cpp b/src/widgets/doc/snippets/qlistview-dnd/mainwindow.cpp
index ed06819dd9..3b19295676 100644
--- a/src/widgets/doc/snippets/qlistview-dnd/mainwindow.cpp
+++ b/src/widgets/doc/snippets/qlistview-dnd/mainwindow.cpp
@@ -38,7 +38,7 @@
 **
 ****************************************************************************/
 
-#include <QtGui>
+#include <QtWidgets>
 
 #include "mainwindow.h"
 #include "model.h"
diff --git a/src/widgets/doc/snippets/qlistview-dnd/model.cpp b/src/widgets/doc/snippets/qlistview-dnd/model.cpp
index 6ebeb2eb56..aa12cef3a2 100644
--- a/src/widgets/doc/snippets/qlistview-dnd/model.cpp
+++ b/src/widgets/doc/snippets/qlistview-dnd/model.cpp
@@ -65,18 +65,31 @@ DragDropListModel::DragDropListModel(const QStringList &strings,
 }
 
 //! [0]
-bool DragDropListModel::dropMimeData(const QMimeData *data,
+bool DragDropListModel::canDropMimeData(const QMimeData *data,
     Qt::DropAction action, int row, int column, const QModelIndex &parent)
 {
-    if (action == Qt::IgnoreAction)
-        return true;
+    Q_UNUSED(action);
+    Q_UNUSED(row);
+    Q_UNUSED(parent);
 
     if (!data->hasFormat("application/vnd.text.list"))
         return false;
 
     if (column > 0)
-//! [0] //! [1]
         return false;
+
+    return true;
+}
+//! [0]
+//! [1]
+bool DragDropListModel::dropMimeData(const QMimeData *data,
+    Qt::DropAction action, int row, int column, const QModelIndex &parent)
+{
+    if (!canDropMimeData(data, action, row, column, parent))
+        return false;
+
+    if (action == Qt::IgnoreAction)
+        return true;
 //! [1]
 
 //! [2]
diff --git a/src/widgets/doc/snippets/qlistview-dnd/model.h b/src/widgets/doc/snippets/qlistview-dnd/model.h
index 9b667ad4a3..9217052971 100644
--- a/src/widgets/doc/snippets/qlistview-dnd/model.h
+++ b/src/widgets/doc/snippets/qlistview-dnd/model.h
@@ -63,6 +63,8 @@ public:
 
     Qt::ItemFlags flags(const QModelIndex &index) const;
 
+    bool canDropMimeData(const QMimeData *data, Qt::DropAction action,
+                         int row, int column, const QModelIndex &parent);
     bool dropMimeData(const QMimeData *data, Qt::DropAction action,
                       int row, int column, const QModelIndex &parent);
     QMimeData *mimeData(const QModelIndexList &indexes) const;
diff --git a/src/widgets/doc/snippets/qlistview-dnd/qlistview-dnd.pro b/src/widgets/doc/snippets/qlistview-dnd/qlistview-dnd.pro
index 71fa273a69..bc2a1f0dce 100644
--- a/src/widgets/doc/snippets/qlistview-dnd/qlistview-dnd.pro
+++ b/src/widgets/doc/snippets/qlistview-dnd/qlistview-dnd.pro
@@ -3,3 +3,4 @@ SOURCES     = main.cpp \
               model.cpp
 HEADERS     = mainwindow.h \
               model.h
+QT += widgets
diff --git a/src/widgets/doc/src/model-view-programming.qdoc b/src/widgets/doc/src/model-view-programming.qdoc
index 8978efa1e3..ada0460689 100644
--- a/src/widgets/doc/src/model-view-programming.qdoc
+++ b/src/widgets/doc/src/model-view-programming.qdoc
@@ -1769,6 +1769,9 @@
     dropped onto existing items separately to data dropped into the top level
     of the model (i.e., onto an invalid item).
 
+    Models can forbid dropping on certain items, or depending on the dropped data,
+    by reimplementing QAbstractItemModel::canDropMimeData().
+
     The model first has to make sure that the operation should be acted on,
     the data supplied is in a format that can be used, and that its destination
     within the model is valid: