Fix crash when using drag with Drag.Automatic

QQuickPointerTouchEvent::m_event is 0 when calling
QQuickPointerTouchEvent::isPressEvent(). Add a convenience function
with a check returning the Qt::TouchPointStates.

Task-number: QTBUG-44976
Change-Id: I2433ec3c56adeda2de190ca46aed8413a1357c55
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

2 files changed, 12 insertions, 3 deletions

diff --git a/src/quick/items/qquickevents.cpp b/src/quick/items/qquickevents.cpp
index 1be4bafe28..3343ea3fa7 100644
--- a/src/quick/items/qquickevents.cpp
+++ b/src/quick/items/qquickevents.cpp
@@ -1572,6 +1572,13 @@ void QQuickPointerTouchEvent::clearGrabbers() const {
     }
 }
 
+Qt::TouchPointStates QQuickPointerTouchEvent::touchPointStates() const
+{
+    return m_event
+        ? static_cast<QTouchEvent*>(m_event)->touchPointStates()
+        : Qt::TouchPointStates();
+}
+
 /*!
     Returns whether the given \a handler is the exclusive grabber of any
     touchpoint within this event.
@@ -1586,17 +1593,17 @@ bool QQuickPointerTouchEvent::hasExclusiveGrabber(const QQuickPointerHandler *ha
 
 bool QQuickPointerTouchEvent::isPressEvent() const
 {
-    return static_cast<QTouchEvent*>(m_event)->touchPointStates() & Qt::TouchPointPressed;
+    return touchPointStates() & Qt::TouchPointPressed;
 }
 
 bool QQuickPointerTouchEvent::isUpdateEvent() const
 {
-    return static_cast<QTouchEvent*>(m_event)->touchPointStates() & (Qt::TouchPointMoved | Qt::TouchPointStationary);
+    return touchPointStates() & (Qt::TouchPointMoved | Qt::TouchPointStationary);
 }
 
 bool QQuickPointerTouchEvent::isReleaseEvent() const
 {
-    return static_cast<QTouchEvent*>(m_event)->touchPointStates() & Qt::TouchPointReleased;
+    return touchPointStates() & Qt::TouchPointReleased;
 }
 
 QVector<QPointF> QQuickPointerEvent::unacceptedPressedPointScenePositions() const
diff --git a/src/quick/items/qquickevents_p_p.h b/src/quick/items/qquickevents_p_p.h
index 2a1e9dc184..00ee0e18f9 100644
--- a/src/quick/items/qquickevents_p_p.h
+++ b/src/quick/items/qquickevents_p_p.h
@@ -510,6 +510,8 @@ public:
     QTouchEvent *asTouchEvent() const;
 
 private:
+    Qt::TouchPointStates touchPointStates() const;
+
     int m_pointCount = 0;
     QVector<QQuickEventTouchPoint *> m_touchPoints;
     mutable QMouseEvent m_synthMouseEvent;