PointerHandlers: fix some grab notification and signal order problems

The singlePointHandlerProperties manual test showed how this was broken
in a couple of ways after 8c659c6c723e4f5f97f46a4555a4765e85c26f1d :
- When QQuickPointerTouchEvent::reset() is swapping one point instance
for another, and consequently transferring the grabbers from one to
another, it should not cause onGrabChanged to occur.  Every point
update was triggering DragHandler.onGrabChanged.
- The order of signal emission is important so that sceneGrabPos
will be correct in onGrabChanged.

Change-Id: I62a302d6e54126ae10834b6d622e82aa0e434bab
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/quick/handlers/qquickpointersinglehandler.cpp b/src/quick/handlers/qquickpointersinglehandler.cpp
index d9a9d692ae..112c680d3c 100644
--- a/src/quick/handlers/qquickpointersinglehandler.cpp
+++ b/src/quick/handlers/qquickpointersinglehandler.cpp
@@ -148,15 +148,17 @@ bool QQuickPointerSingleHandler::wantsEventPoint(QQuickEventPoint *point)
 
 void QQuickPointerSingleHandler::onGrabChanged(QQuickPointerHandler *grabber, QQuickEventPoint::GrabState stateChange, QQuickEventPoint *point)
 {
-    QQuickPointerHandler::onGrabChanged(grabber, stateChange, point);
     if (grabber != this)
         return;
     switch (stateChange) {
     case QQuickEventPoint::GrabExclusive:
+        m_sceneGrabPos = point->sceneGrabPos();
         setActive(true);
-        Q_FALLTHROUGH();
+        QQuickPointerHandler::onGrabChanged(grabber, stateChange, point);
+        break;
     case QQuickEventPoint::GrabPassive:
         m_sceneGrabPos = point->sceneGrabPos();
+        QQuickPointerHandler::onGrabChanged(grabber, stateChange, point);
         break;
     case QQuickEventPoint::OverrideGrabPassive:
         return; // don't emit
@@ -165,6 +167,7 @@ void QQuickPointerSingleHandler::onGrabChanged(QQuickPointerHandler *grabber, QQ
     case QQuickEventPoint::CancelGrabPassive:
     case QQuickEventPoint::CancelGrabExclusive:
         // the grab is lost or relinquished, so the point is no longer relevant
+        QQuickPointerHandler::onGrabChanged(grabber, stateChange, point);
         reset();
         break;
     }