Fix drag and drop regression

Fix regression introduced by e4becdc3d310a0dd1a6d34d0796a52b21dedeb2d

Add QPlatformDrag::ownsDragObject() function, QDragManager can use the
return value of this function to decide if it should take care of deleting
QDrag object or platform plugin will take care of deleting QDrag.

XCB platform plugins uses async dnd data delivery mechanism. It allows
user to drop something and then continue working with the assurance that
the target will get the data regardless of how slow the network connections
are, which means that a source window should preserve QDrag data until
dnd has finished.

Change-Id: I1fbad7380cddec98b756698993dd397409833150
Task-number: QTBUG-43436
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/plugins/platforms/xcb/qxcbdrag.cpp b/src/plugins/platforms/xcb/qxcbdrag.cpp
index 7037e102e2..ec0399ed5f 100644
--- a/src/plugins/platforms/xcb/qxcbdrag.cpp
+++ b/src/plugins/platforms/xcb/qxcbdrag.cpp
@@ -999,6 +999,8 @@ void QXcbDrag::handleFinished(const xcb_client_message_event_t *event)
         if (at != -1) {
 
             Transaction t = transactions.takeAt(at);
+            if (t.drag)
+                t.drag->deleteLater();
 //            QDragManager *manager = QDragManager::self();
 
 //            Window target = current_target;
@@ -1186,6 +1188,11 @@ bool QXcbDrag::dndEnable(QXcbWindow *w, bool on)
     }
 }
 
+bool QXcbDrag::ownsDragObject() const
+{
+    return true;
+}
+
 QXcbDropData::QXcbDropData(QXcbDrag *d)
     : QXcbMime(),
       drag(d)