Start over with event delivery when touchpoint releases occur

The new rule is that when the number of touchpoints changes, we start
over with event delivery as if the touch had just begun, to give more
opportunities to hand off processing from one item or handler to
another.  And MultiPointTouchArea can now handle the handoff:
for example in tests/manual/pointer/pinchDragFlingMPTA.qml when the
user is pressing three fingers, the PinchHandler is active; when the
user then lifts one finger, the MPTA can resume handling the two
remaining touchpoints as if they were just pressed.

The change in QQuickMultiPointerHandler::wantsPointerEvent is both
a behavior change and an optimization: released points aren't eligible;
but if some points are released, then pressed, updated and stationary
points are all eligible. And, figure this out without looping over the
points twice.

Change-Id: I26b7593de8e72b471adfec4a4482dd87a8288442
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/quick/items/qquickwindow_p.h b/src/quick/items/qquickwindow_p.h
index f66809cc8a..fa39eca9a6 100644
--- a/src/quick/items/qquickwindow_p.h
+++ b/src/quick/items/qquickwindow_p.h
@@ -168,9 +168,9 @@ public:
     void deliverPointerEvent(QQuickPointerEvent *);
     void deliverTouchEvent(QQuickPointerTouchEvent *);
     bool deliverTouchCancelEvent(QTouchEvent *);
-    bool deliverPressEvent(QQuickPointerEvent *);
+    bool deliverPressOrReleaseEvent(QQuickPointerEvent *, bool handlersOnly = false);
     void deliverUpdatedTouchPoints(QQuickPointerTouchEvent *event);
-    void deliverMatchingPointsToItem(QQuickItem *item, QQuickPointerEvent *pointerEvent);
+    void deliverMatchingPointsToItem(QQuickItem *item, QQuickPointerEvent *pointerEvent, bool handlersOnly = false);
 
     QVector<QQuickItem *> pointerTargets(QQuickItem *, const QPointF &, bool checkMouseButtons, bool checkAcceptsTouch) const;
     QVector<QQuickItem *> mergePointerTargets(const QVector<QQuickItem *> &list1, const QVector<QQuickItem *> &list2) const;