Make sure we don't modify the incoming event objects when localizing

Restore the position of the single event point after event delivery.

Where possible, don't make a localized copy which explicitly shares
its data with the original anyway. Instead, access the original
directly.

Change-Id: I5efa44c336eddeef1a1ab00dc91e2d0f223ed31d
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

2 files changed, 9 insertions, 4 deletions

diff --git a/src/quick/items/qquickflickable.cpp b/src/quick/items/qquickflickable.cpp
index b451c275c2..2401f008aa 100644
--- a/src/quick/items/qquickflickable.cpp
+++ b/src/quick/items/qquickflickable.cpp
@@ -1452,9 +1452,12 @@ void QQuickFlickable::mouseReleaseEvent(QMouseEvent *event)
 
             // Now send the release
             if (auto grabber = qmlobject_cast<QQuickItem *>(event->exclusiveGrabber(event->point(0)))) {
-                QMutableSinglePointEvent localized(*event);
-                localized.mutablePoint().setPosition(grabber->mapFromScene(localized.scenePosition()));
-                QCoreApplication::sendEvent(window(), &localized);
+                // not copying or detaching anything, so make sure we return the original event unchanged
+                QMutableSinglePointEvent *localized = QMutableSinglePointEvent::from(event);
+                const auto oldPosition = localized->mutablePoint().position();
+                localized->mutablePoint().setPosition(grabber->mapFromScene(localized->scenePosition()));
+                QCoreApplication::sendEvent(window(), localized);
+                localized->mutablePoint().setPosition(oldPosition);
             }
 
             // And the event has been consumed
diff --git a/src/quick/items/qquickmultipointtoucharea.cpp b/src/quick/items/qquickmultipointtoucharea.cpp
index e23e7365df..ed424a3763 100644
--- a/src/quick/items/qquickmultipointtoucharea.cpp
+++ b/src/quick/items/qquickmultipointtoucharea.cpp
@@ -902,13 +902,14 @@ void QQuickMultiPointTouchArea::touchUngrabEvent()
 
 bool QQuickMultiPointTouchArea::sendMouseEvent(QMouseEvent *event)
 {
-    QPointF localPos = mapFromScene(event->scenePosition());
+    const QPointF localPos = mapFromScene(event->scenePosition());
 
     QQuickWindow *c = window();
     QQuickItem *grabber = c ? c->mouseGrabberItem() : nullptr;
     bool stealThisEvent = _stealMouse;
     if ((stealThisEvent || contains(localPos)) && (!grabber || !grabber->keepMouseGrab())) {
         QMutableSinglePointEvent mouseEvent(*event);
+        const auto oldPosition = mouseEvent.mutablePoint().position();
         mouseEvent.mutablePoint().setPosition(localPos);
         mouseEvent.setSource(Qt::MouseEventSynthesizedByQt);
         mouseEvent.setAccepted(false);
@@ -931,6 +932,7 @@ bool QQuickMultiPointTouchArea::sendMouseEvent(QMouseEvent *event)
         if (grabber && stealThisEvent && !grabber->keepMouseGrab() && grabber != this)
             grabMouse();
 
+        mouseEvent.mutablePoint().setPosition(oldPosition);
         return stealThisEvent;
     }
     if (event->type() == QEvent::MouseButtonRelease) {