Add assertions and checks on QQWinPriv::deliveryAgentPrivate()

The static analyzer found the case where it could actually be null
during delivery of a WindowDeactivate event.  In other cases, we assert
rather than testing, until we know that it can actually be null.  It
shouldn't often be null because it's created in QQuickWindowPrivate::init()
and destroyed in the destructor; however we've already seen races when
event delivery continues while the window is being destroyed.  If more
such cases materialize, we can replace asserts with if()'s or check
the new inDestructor flag.

Fixes static analyzer warning 16738055c4c458145b59ad9b6bb643b5

Change-Id: I408e9a7d71a77fd29c2af91e59caf9ede6585af9
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit fb69e86bee67a228ca581a8bfe3384da14398f76)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 55 insertions, 23 deletions

diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index 85b59aa7ba..a3d8b5eacb 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -803,8 +803,11 @@ void QQuickWindowPrivate::init(QQuickWindow *c, QQuickRenderControl *control)
 void QQuickWindow::handleApplicationStateChanged(Qt::ApplicationState state)
 {
     Q_D(QQuickWindow);
-    if (state != Qt::ApplicationActive && d->contentItem)
-        d->deliveryAgentPrivate()->handleWindowDeactivate(this);
+    if (state != Qt::ApplicationActive && d->contentItem) {
+        auto da = d->deliveryAgentPrivate();
+        Q_ASSERT(da);
+        da->handleWindowDeactivate(this);
+    }
 }
 
 /*!
@@ -836,13 +839,21 @@ void QQuickWindowPrivate::dirtyItem(QQuickItem *)
 QQuickItem *QQuickWindow::mouseGrabberItem() const
 {
     Q_D(const QQuickWindow);
-    auto epd = const_cast<QQuickWindowPrivate *>(d)->deliveryAgentPrivate()->mousePointData();
-    if (!epd && d->deliveryAgentPrivate()->eventsInDelivery.isEmpty()) {
+    auto da = const_cast<QQuickWindowPrivate *>(d)->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    // The normal use case is to call this function while an event is being delivered;
+    // but if the caller knows about the event, it should call QPointerEvent::exclusiveGrabber() instead.
+    if (auto epd = da->mousePointData())
+        return qmlobject_cast<QQuickItem *>(epd->exclusiveGrabber);
+
+    if (Q_LIKELY(d->deliveryAgentPrivate()->eventsInDelivery.isEmpty()))
+        // mousePointData() checked that already: it's one reason epd can be null
         qCDebug(lcMouse, "mouse grabber ambiguous: no event is currently being delivered");
-        return qmlobject_cast<QQuickItem *>(QPointingDevicePrivate::get(QPointingDevice::primaryPointingDevice())->
-                                            firstPointExclusiveGrabber());
-    }
-    return qobject_cast<QQuickItem *>(epd->exclusiveGrabber);
+    // If no event is being delivered, we can return "the mouse" grabber,
+    // but in general there could be more than one mouse, could be only a touchscreen etc.
+    // That's why this function is obsolete.
+    return qmlobject_cast<QQuickItem *>(QPointingDevicePrivate::get(QPointingDevice::primaryPointingDevice())->
+                                        firstPointExclusiveGrabber());
 }
 
 void QQuickWindowPrivate::cleanup(QSGNode *n)
@@ -1302,8 +1313,9 @@ QQuickItem *QQuickWindow::contentItem() const
 QQuickItem *QQuickWindow::activeFocusItem() const
 {
     Q_D(const QQuickWindow);
-
-    return d->deliveryAgentPrivate()->activeFocusItem;
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    return da->activeFocusItem;
 }
 
 /*!
@@ -1313,9 +1325,10 @@ QQuickItem *QQuickWindow::activeFocusItem() const
 QObject *QQuickWindow::focusObject() const
 {
     Q_D(const QQuickWindow);
-
-    if (!d->inDestructor && d->deliveryAgentPrivate()->activeFocusItem)
-        return d->deliveryAgentPrivate()->activeFocusItem;
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    if (!d->inDestructor && da->activeFocusItem)
+        return da->activeFocusItem;
     return const_cast<QQuickWindow*>(this);
 }
 
@@ -1435,7 +1448,8 @@ bool QQuickWindow::event(QEvent *e)
         }
         break;
     case QEvent::WindowDeactivate:
-        d->deliveryAgentPrivate()->handleWindowDeactivate(this);
+        if (auto da = d->deliveryAgentPrivate())
+            da->handleWindowDeactivate(this);
         break;
     default:
         break;
@@ -1453,14 +1467,18 @@ bool QQuickWindow::event(QEvent *e)
 void QQuickWindow::keyPressEvent(QKeyEvent *e)
 {
     Q_D(QQuickWindow);
-    d->deliveryAgentPrivate()->deliverKeyEvent(e);
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    da->deliverKeyEvent(e);
 }
 
 /*! \reimp */
 void QQuickWindow::keyReleaseEvent(QKeyEvent *e)
 {
     Q_D(QQuickWindow);
-    d->deliveryAgentPrivate()->deliverKeyEvent(e);
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    da->deliverKeyEvent(e);
 }
 
 #if QT_CONFIG(wheelevent)
@@ -1468,7 +1486,9 @@ void QQuickWindow::keyReleaseEvent(QKeyEvent *e)
 void QQuickWindow::wheelEvent(QWheelEvent *event)
 {
     Q_D(QQuickWindow);
-    d->deliveryAgentPrivate()->deliverSinglePointEventUntilAccepted(event);
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    da->deliverSinglePointEventUntilAccepted(event);
 }
 #endif // wheelevent
 
@@ -1477,7 +1497,9 @@ void QQuickWindow::wheelEvent(QWheelEvent *event)
 void QQuickWindow::tabletEvent(QTabletEvent *event)
 {
     Q_D(QQuickWindow);
-    d->deliveryAgentPrivate()->deliverPointerEvent(event);
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    da->deliverPointerEvent(event);
 }
 #endif // tabletevent
 
@@ -1485,31 +1507,41 @@ void QQuickWindow::tabletEvent(QTabletEvent *event)
 void QQuickWindow::mousePressEvent(QMouseEvent *event)
 {
     Q_D(QQuickWindow);
-    d->deliveryAgentPrivate()->handleMouseEvent(event);
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    da->handleMouseEvent(event);
 }
 /*! \reimp */
 void QQuickWindow::mouseMoveEvent(QMouseEvent *event)
 {
     Q_D(QQuickWindow);
-    d->deliveryAgentPrivate()->handleMouseEvent(event);
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    da->handleMouseEvent(event);
 }
 /*! \reimp */
 void QQuickWindow::mouseDoubleClickEvent(QMouseEvent *event)
 {
     Q_D(QQuickWindow);
-    d->deliveryAgentPrivate()->handleMouseEvent(event);
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    da->handleMouseEvent(event);
 }
 /*! \reimp */
 void QQuickWindow::mouseReleaseEvent(QMouseEvent *event)
 {
     Q_D(QQuickWindow);
-    d->deliveryAgentPrivate()->handleMouseEvent(event);
+    auto da = d->deliveryAgentPrivate();
+    Q_ASSERT(da);
+    da->handleMouseEvent(event);
 }
 
 void QQuickWindowPrivate::flushFrameSynchronousEvents()
 {
     Q_Q(QQuickWindow);
-    deliveryAgentPrivate()->flushFrameSynchronousEvents(q);
+    auto da = deliveryAgentPrivate();
+    Q_ASSERT(da);
+    da->flushFrameSynchronousEvents(q);
 }
 
 #if QT_CONFIG(cursor)