Fix ubsan warning of illegal cast and illegal method call

Avoid casting an event to a type it does not have. Instead use a static accessor class.

Task-number: QTBUG-99563
Change-Id: Ideb11779b1510cd10a27fb8bc40bcc8e4849bf15
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
(cherry picked from commit acc3ef6653c710b509e9321663986910f88ac3b4)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/gui/kernel/qevent.cpp

@@ -4804,19 +4804,27 @@ QMutableTouchEvent::~QMutableTouchEvent()
 /*! \internal
     Add the given \a point.
 */
-void QMutableTouchEvent::addPoint(const QEventPoint &point)
+void QMutableTouchEvent::addPoint(QTouchEvent *e, const QEventPoint &point)
 {
-    m_points.append(point);
-    auto &added = m_points.last();
+    e->m_points.append(point);
+    auto &added = e->m_points.last();
     if (!added.device())
-        QMutableEventPoint::setDevice(added, pointingDevice());
-    m_touchPointStates |= point.state();
+        QMutableEventPoint::setDevice(added, e->pointingDevice());
+    e->m_touchPointStates |= point.state();
 }
 
 
 QMutableSinglePointEvent::~QMutableSinglePointEvent()
     = default;
 
+/*! \internal
+    Add the given \a point.
+*/
+void QMutableTouchEvent::addPoint(const QEventPoint &point)
+{
+    addPoint(this, point);
+}
+
 QT_END_NAMESPACE
 
 #include "moc_qevent.cpp"

src/gui/kernel/qevent.h

@@ -134,6 +134,7 @@ public:
 
 protected:
     friend class ::tst_QEvent;
+    friend class QMutableSinglePointEvent;
     QSinglePointEvent(Type type, const QPointingDevice *dev, const QEventPoint &point,
                       Qt::MouseButton button, Qt::MouseButtons buttons,
                       Qt::KeyboardModifiers modifiers, Qt::MouseEventSource source);
@@ -943,6 +944,7 @@ public:
     bool isEndEvent() const override;
 
 protected:
+    friend class QMutableTouchEvent;
     QObject *m_target = nullptr;
     QEventPoint::States m_touchPointStates = QEventPoint::State::Unknown;
     quint32 m_reserved : 24;

src/gui/kernel/qevent_p.h

@@ -39,8 +39,10 @@ public:
     static QMutableTouchEvent &from(QTouchEvent &e) { return static_cast<QMutableTouchEvent &>(e); }
 
     void setTarget(QObject *target) { m_target = target; }
-
     void addPoint(const QEventPoint &point);
+
+    static void setTarget(QTouchEvent *e, QObject *target) { e->m_target = target; }
+    static void addPoint(QTouchEvent *e, const QEventPoint &point);
 };
 
 class Q_GUI_EXPORT QMutableSinglePointEvent : public QSinglePointEvent
@@ -63,6 +65,16 @@ public:
     bool isDoubleClick() { return m_doubleClick; }
 
     void setDoubleClick(bool d = true) { m_doubleClick = d; }
+
+    static bool isDoubleClick(const QSinglePointEvent *ev)
+    {
+        return ev->m_doubleClick;
+    }
+
+    static void setDoubleClick(QSinglePointEvent *ev, bool d)
+    {
+        ev->m_doubleClick = d;
+    }
 };
 
 QT_END_NAMESPACE

src/gui/kernel/qguiapplication.cpp

@@ -2455,7 +2455,7 @@ void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::Mo
 
     if (doubleClick && (ev.type() == QEvent::MouseButtonPress)) {
         // QtBUG-25831, used to suppress delivery in qwidgetwindow.cpp
-        QMutableSinglePointEvent::from(ev).setDoubleClick();
+        QMutableSinglePointEvent::setDoubleClick(&ev, true);
     }
 
     QGuiApplication::sendSpontaneousEvent(window, &ev);

src/gui/kernel/qpointingdevice.cpp

@@ -407,7 +407,7 @@ void QPointingDevicePrivate::sendTouchCancelEvent(QTouchEvent *cancelEvent)
     if (cancelEvent->points().isEmpty()) {
         for (auto &epd : activePoints.values()) {
             if (epd.exclusiveGrabber)
-                QMutableTouchEvent::from(cancelEvent)->addPoint(epd.eventPoint);
+                QMutableTouchEvent::addPoint(cancelEvent, epd.eventPoint);
         }
     }
     for (auto &epd : activePoints.values()) {

src/widgets/graphicsview/qgraphicsview.cpp

@@ -2902,7 +2902,7 @@ bool QGraphicsView::viewportEvent(QEvent *event)
         if (d->scene && d->sceneInteractionAllowed) {
             // Convert and deliver the touch event to the scene.
             QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
-            QMutableTouchEvent::from(touchEvent)->setTarget(viewport());
+            QMutableTouchEvent::setTarget(touchEvent, viewport());
             QGraphicsViewPrivate::translateTouchEvent(d, touchEvent);
             QCoreApplication::sendEvent(d->scene, touchEvent);
         } else {

src/widgets/kernel/qapplication.cpp

@@ -2762,7 +2762,7 @@ bool QApplication::notify(QObject *receiver, QEvent *e)
                                mouse->pointingDevice());
                 me.m_spont = mouse->spontaneous();
                 me.setTimestamp(mouse->timestamp());
-                QMutableSinglePointEvent::from(me).setDoubleClick(QMutableSinglePointEvent::from(mouse)->isDoubleClick());
+                QMutableSinglePointEvent::setDoubleClick(&me, QMutableSinglePointEvent::isDoubleClick(mouse));
                 // throw away any mouse-tracking-only mouse events
                 if (!w->hasMouseTracking()
                     && mouse->type() == QEvent::MouseMove && mouse->buttons() == 0) {
@@ -3067,7 +3067,7 @@ bool QApplication::notify(QObject *receiver, QEvent *e)
 #endif // QT_CONFIG(draganddrop)
         case QEvent::TouchBegin: {
             // Note: TouchUpdate and TouchEnd events are never propagated
-            QMutableTouchEvent *touchEvent = QMutableTouchEvent::from(static_cast<QTouchEvent *>(e));
+            QTouchEvent *touchEvent = static_cast<QTouchEvent *>(e);
             bool eventAccepted = touchEvent->isAccepted();
             bool acceptTouchEvents = w->testAttribute(Qt::WA_AcceptTouchEvents);
 
@@ -3084,7 +3084,7 @@ bool QApplication::notify(QObject *receiver, QEvent *e)
             while (w) {
                 // first, try to deliver the touch event
                 acceptTouchEvents = w->testAttribute(Qt::WA_AcceptTouchEvents);
-                touchEvent->setTarget(w);
+                QMutableTouchEvent::setTarget(touchEvent, w);
                 touchEvent->setAccepted(acceptTouchEvents);
                 QPointer<QWidget> p = w;
                 res = acceptTouchEvents && d->notify_helper(w, touchEvent);
@@ -3110,7 +3110,7 @@ bool QApplication::notify(QObject *receiver, QEvent *e)
 
                 const QPoint offset = w->pos();
                 w = w->parentWidget();
-                touchEvent->setTarget(w);
+                QMutableTouchEvent::setTarget(touchEvent, w);
                 for (int i = 0; i < touchEvent->pointCount(); ++i) {
                     auto &pt = touchEvent->point(i);
                     QMutableEventPoint::setPosition(pt, pt.position() + offset);

src/widgets/kernel/qwidgetwindow.cpp

@@ -564,7 +564,7 @@ void QWidgetWindow::handleMouseEvent(QMouseEvent *event)
                 }
             }
 
-            if ((event->type() != QEvent::MouseButtonPress) || !(QMutableSinglePointEvent::from(event)->isDoubleClick())) {
+            if ((event->type() != QEvent::MouseButtonPress) || !(QMutableSinglePointEvent::isDoubleClick(event))) {
                 // if the widget that was pressed is gone, then deliver move events without buttons
                 const auto buttons = event->type() == QEvent::MouseMove && qt_popup_down_closed
                                    ? Qt::NoButton : event->buttons();
@@ -656,7 +656,7 @@ void QWidgetWindow::handleMouseEvent(QMouseEvent *event)
         mapped = event->position().toPoint();
     }
 
-    if ((event->type() != QEvent::MouseButtonPress) || !QMutableSinglePointEvent::from(event)->isDoubleClick()) {
+    if ((event->type() != QEvent::MouseButtonPress) || !QMutableSinglePointEvent::isDoubleClick(event)) {
 
         // The preceding statement excludes MouseButtonPress events which caused
         // creation of a MouseButtonDblClick event. QTBUG-25831