QTouchEvent::TouchPoint: make it a proper value class

This includes:
- Marking it as Q_MOVABLE_TYPE
- adding move ctor and move assignment operator
- add member-swap
- use the copy-swap idiom in the copy-assignment operator

This required making the destructor safe for d == nullptr.

Change-Id: I8a77ffcb8e4a395a7e103d1df610561b6ae4c001
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/gui/kernel/qevent.cpp

@@ -3621,7 +3621,7 @@ QTouchEvent::TouchPoint::TouchPoint(const QTouchEvent::TouchPoint &other)
 */
 QTouchEvent::TouchPoint::~TouchPoint()
 {
-    if (!d->ref.deref())
+    if (d && !d->ref.deref())
         delete d;
 }
 
@@ -4043,16 +4043,15 @@ void QTouchEvent::TouchPoint::setFlags(InfoFlags flags)
     d->flags = flags;
 }
 
-/*! \internal */
-QTouchEvent::TouchPoint &QTouchEvent::TouchPoint::operator=(const QTouchEvent::TouchPoint &other)
-{
-    other.d->ref.ref();
-    if (!d->ref.deref())
-        delete d;
-    d = other.d;
-    return *this;
-}
+/*!
+    \fn QTouchEvent::TouchPoint &QTouchEvent::TouchPoint::operator=(const QTouchEvent::TouchPoint &other)
+    \internal
+ */
 
+/*!
+    \fn void QTouchEvent::TouchPoint::swap(TouchPoint &other);
+    \internal
+*/
 
 /*!
     \class QScrollPrepareEvent

src/gui/kernel/qevent.h

@@ -713,9 +713,19 @@ public:
         Q_DECLARE_FLAGS(InfoFlags, InfoFlag)
 
         explicit TouchPoint(int id = -1);
-        TouchPoint(const QTouchEvent::TouchPoint &other);
+        TouchPoint(const TouchPoint &other);
+#ifdef Q_COMPILER_RVALUE_REFS
+        TouchPoint(TouchPoint &&other) : d(other.d) { other.d = 0; }
+        TouchPoint &operator=(TouchPoint &&other)
+        { qSwap(d, other.d); return *this; }
+#endif
         ~TouchPoint();
 
+        TouchPoint &operator=(const TouchPoint &other)
+        { if ( d != other.d ) { TouchPoint copy(other); swap(copy); } return *this; }
+
+        void swap(TouchPoint &other) { qSwap(d, other.d); }
+
         int id() const;
 
         Qt::TouchPointState state() const;
@@ -767,7 +777,6 @@ public:
         void setVelocity(const QVector2D &v);
         void setFlags(InfoFlags flags);
         void setRawScreenPositions(const QList<QPointF> &positions);
-        QTouchEvent::TouchPoint &operator=(const QTouchEvent::TouchPoint &other);
 
     private:
         QTouchEventTouchPointPrivate *d;
@@ -819,7 +828,7 @@ protected:
     friend class QApplication;
     friend class QApplicationPrivate;
 };
-
+Q_DECLARE_TYPEINFO(QTouchEvent::TouchPoint, Q_MOVABLE_TYPE);
 Q_DECLARE_OPERATORS_FOR_FLAGS(QTouchEvent::TouchPoint::InfoFlags)
 
 class QScrollPrepareEventPrivate;