From 0613e8f4c9305aba3f6a5992ab36f32641a88585 Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Wed, 11 Nov 2020 15:59:49 +0200
Subject: [PATCH] Safely end drag if the source data device gets destroyed

We cannot end a drag after the destroyed() signal for the source data
device is emitted because DataDeviceInterface and its d pointer are gone
by that time.
---
 src/wayland/datadevice_interface.cpp |  1 +
 src/wayland/datadevice_interface.h   |  1 +
 src/wayland/seat_interface.cpp       | 30 +++++++++++++---------------
 src/wayland/seat_interface_p.h       |  1 +
 4 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/src/wayland/datadevice_interface.cpp b/src/wayland/datadevice_interface.cpp
index 29b6d8f49b..6ff8c13459 100644
--- a/src/wayland/datadevice_interface.cpp
+++ b/src/wayland/datadevice_interface.cpp
@@ -175,6 +175,7 @@ DataOfferInterface *DataDeviceInterfacePrivate::createDataOffer(AbstractDataSour
 void DataDeviceInterfacePrivate::data_device_destroy_resource(QtWaylandServer::wl_data_device::Resource *resource)
 {
     Q_UNUSED(resource)
+    emit q->aboutToBeDestroyed();
     delete q;
 }
 
diff --git a/src/wayland/datadevice_interface.h b/src/wayland/datadevice_interface.h
index 991220a23b..a0d6fe5a89 100644
--- a/src/wayland/datadevice_interface.h
+++ b/src/wayland/datadevice_interface.h
@@ -118,6 +118,7 @@ public:
     wl_client *client();
 
 Q_SIGNALS:
+    void aboutToBeDestroyed();
     void dragStarted();
     void selectionChanged(KWaylandServer::DataSourceInterface*);
     void selectionCleared();
diff --git a/src/wayland/seat_interface.cpp b/src/wayland/seat_interface.cpp
index a1e1d191a3..2c536eaaad 100644
--- a/src/wayland/seat_interface.cpp
+++ b/src/wayland/seat_interface.cpp
@@ -293,20 +293,15 @@ void SeatInterface::Private::registerDataDevice(DataDeviceInterface *dataDevice)
             }
             drag.source = dataDevice;
             drag.sourcePointer = interfaceForSurface(originSurface, pointers);
-            drag.destroyConnection = QObject::connect(dataDevice, &QObject::destroyed, q,
+            drag.destroyConnection = QObject::connect(dataDevice, &DataDeviceInterface::aboutToBeDestroyed, q,
                 [this] {
-                    endDrag(display->nextSerial());
+                    cancelDrag(display->nextSerial());
                 }
             );
             if (dataDevice->dragSource()) {
                 drag.dragSourceDestroyConnection = QObject::connect(dataDevice->dragSource(), &AbstractDataSource::aboutToBeDestroyed, q,
                     [this] {
-                        const auto serial = display->nextSerial();
-                        if (drag.target) {
-                            drag.target->updateDragTarget(nullptr, serial);
-                            drag.target = nullptr;
-                        }
-                        endDrag(serial);
+                        cancelDrag(display->nextSerial());
                     }
                 );
             } else {
@@ -395,6 +390,15 @@ void SeatInterface::Private::registerPrimarySelectionDevice(PrimarySelectionDevi
     }
 }
 
+void SeatInterface::Private::cancelDrag(quint32 serial)
+{
+    if (drag.target) {
+        drag.target->updateDragTarget(nullptr, serial);
+        drag.target = nullptr;
+    }
+    endDrag(serial);
+}
+
 void SeatInterface::Private::endDrag(quint32 serial)
 {
     QObject::disconnect(drag.destroyConnection);
@@ -1215,14 +1219,8 @@ void SeatInterface::cancelTouchSequence()
         (*it)->cancel();
     }
     if (d->drag.mode == Private::Drag::Mode::Touch) {
-        // cancel the drag, don't drop.
-        if (d->drag.target) {
-            // remove the current target
-            d->drag.target->updateDragTarget(nullptr, 0);
-            d->drag.target = nullptr;
-        }
-        // and end the drag for the source, serial does not matter
-        d->endDrag(0);
+        // cancel the drag, don't drop. serial does not matter
+        d->cancelDrag(0);
     }
     d->globalTouch.ids.clear();
 }
diff --git a/src/wayland/seat_interface_p.h b/src/wayland/seat_interface_p.h
index 81ebe4f9e3..9b16dd6fb5 100644
--- a/src/wayland/seat_interface_p.h
+++ b/src/wayland/seat_interface_p.h
@@ -42,6 +42,7 @@ public:
     void registerDataDevice(DataDeviceInterface *dataDevice);
     void registerDataControlDevice(DataControlDeviceV1Interface *dataDevice);
     void endDrag(quint32 serial);
+    void cancelDrag(quint32 serial);
     quint32 nextSerial() const;
 
     QString name;