Handle ungrab and grab-cancel consistently; inform handlers

Call onGrabChanged on Pointer Handlers during grab transitions:
this was missing in a97759a336c597327cb82eebc9f45c793aec32c9.

Flickable needs to receive an ungrab by child-event-filtering,
in order to set its pressed state back to false (as in the
cancelOnHide autotest).  This is best done as a result of the
QPointingDevice::grabChanged signal, while trying to send the ungrab
to the item that was the grabber, rather than as a special case.

Thus, QQuickWindowPrivate::onGrabChanged (the handler for the
QPointingDevice::grabChanged signal) is now the only place from which
we call QQuickItem::mouseUngrabEvent() and touchUngrabEvent().
But the result is that they are called in more cases than before,
so some tests need adjustment.  touchUngrabEvent() is not sent
unless the event is available and we can verify that all points
have been released.  This is important for MultiPointTouchArea:
it will react by ending interaction with all points at once.

Another thing that's important to MPTA and multi-touch handlers is that
QQuickWindowPrivate::deliverPointerEvent() must not clear grabbers of
points that are not yet released, in the case that only some points are.

QQuickWindowPrivate::removeGrabber() now calls
QPointingDevicePrivate::removeGrabber() with its optional cancel
argument, so that it will emit either a cancel or an ungrab transition.
That's only relevant for Pointer Handlers, whereas QQuickItem
mouseUngrabEvent and touchUngrabEvent don't make a distinction.

Task-number: QTBUG-86729
Change-Id: Idf03aef2e2182398e0fc4a606c0ddbb2aaed5681
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

3 files changed, 44 insertions, 34 deletions

diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index de43f2fb7d..d482dcdfca 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -6058,7 +6058,7 @@ bool QQuickItemPrivate::setEffectiveVisibleRecur(bool newEffectiveVisible)
 
     if (window) {
         QQuickWindowPrivate *windowPriv = QQuickWindowPrivate::get(window);
-        windowPriv->removeGrabber(q);
+        windowPriv->removeGrabber(q, true, true, true);
     }
 
     bool childVisibilityChanged = false;
@@ -6105,7 +6105,7 @@ void QQuickItemPrivate::setEffectiveEnableRecur(QQuickItem *scope, bool newEffec
 
     if (window) {
         QQuickWindowPrivate *windowPriv = QQuickWindowPrivate::get(window);
-        windowPriv->removeGrabber(q);
+        windowPriv->removeGrabber(q, true, true, true);
         if (scope && !effectiveEnable && activeFocus) {
             windowPriv->clearFocusInScope(
                     scope, q, Qt::OtherFocusReason, QQuickWindowPrivate::DontChangeFocusProperty | QQuickWindowPrivate::DontChangeSubFocusItem);
diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index b32b40e8fd..a2cf478f68 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -1049,14 +1049,14 @@ bool QQuickWindowPrivate::deliverTouchAsMouse(QQuickItem *item, QTouchEvent *poi
     but if not all points are released, it cannot be sure whether to call touchUngrabEvent()
     or not; so we have to do it here.
 */
-void QQuickWindowPrivate::removeGrabber(QQuickItem *grabber, bool mouse, bool touch)
+void QQuickWindowPrivate::removeGrabber(QQuickItem *grabber, bool mouse, bool touch, bool cancel)
 {
     Q_Q(QQuickWindow);
     if (eventsInDelivery.isEmpty()) {
         // do it the expensive way
         for (auto dev : knownPointingDevices) {
             auto devPriv = QPointingDevicePrivate::get(const_cast<QPointingDevice *>(dev));
-            devPriv->removeGrabber(grabber);
+            devPriv->removeGrabber(grabber, cancel);
         }
         return;
     }
@@ -1084,19 +1084,6 @@ void QQuickWindowPrivate::removeGrabber(QQuickItem *grabber, bool mouse, bool to
     }
 }
 
-void QQuickWindowPrivate::sendUngrabEvent(QQuickItem *grabber, bool touch)
-{
-    if (!grabber)
-        return;
-    QEvent e(QEvent::UngrabMouse);
-    hasFiltered.clear();
-    if (!sendFilteredMouseEvent(&e, grabber, grabber->parentItem())) {
-        grabber->mouseUngrabEvent();
-        if (touch)
-            grabber->touchUngrabEvent();
-    }
-}
-
 /*! \internal
     Translates QEventPoint::scenePosition() in \a touchEvent to this window.
 
@@ -2265,11 +2252,6 @@ bool QQuickWindowPrivate::deliverTouchCancelEvent(QTouchEvent *event)
 {
     qCDebug(DBG_TOUCH) << event;
 
-    if (isDeliveringTouchAsMouse()) {
-        if (QQuickItem *grabber = qmlobject_cast<QQuickItem *>(event->exclusiveGrabber(touchMouseId)))
-            sendUngrabEvent(grabber, true);
-    }
-
     // An incoming TouchCancel event will typically not contain any points,
     // but sendTouchCancelEvent() adds the points that have grabbers to the event.
     // Deliver it to all items and handlers that have active touches.
@@ -2579,14 +2561,41 @@ void QQuickWindowPrivate::onGrabChanged(QObject *grabber, QPointingDevice::GrabT
                                         const QPointerEvent *event, const QEventPoint &point)
 {
     qCDebug(lcPtrGrab) << grabber << transition << event << point;
-    // event can be null, if the signal was emitted from QPointingDevicePrivate::removeGrabber(grabber)
-    switch (transition) {
-    case QPointingDevice::UngrabExclusive:
-        if (point.device()->type() == QInputDevice::DeviceType::Mouse || isDeliveringTouchAsMouse())
-            sendUngrabEvent(qobject_cast<QQuickItem *>(grabber), isDeliveringTouchAsMouse());
-        break;
-    default:
-        break;
+    // note: event can be null, if the signal was emitted from QPointingDevicePrivate::removeGrabber(grabber)
+    if (auto *handler = qmlobject_cast<QQuickPointerHandler *>(grabber)) {
+        handler->onGrabChanged(handler, transition, const_cast<QPointerEvent *>(event),
+                               const_cast<QEventPoint &>(point));
+    } else {
+        switch (transition) {
+        case QPointingDevice::CancelGrabExclusive:
+        case QPointingDevice::UngrabExclusive:
+            if (auto *item = qmlobject_cast<QQuickItem *>(grabber)) {
+                bool filtered = false;
+                if (isDeliveringTouchAsMouse() ||
+                        point.device()->type() == QInputDevice::DeviceType::Mouse ||
+                        point.device()->type() == QInputDevice::DeviceType::TouchPad) {
+                    QEvent e(QEvent::UngrabMouse);
+                    hasFiltered.clear();
+                    filtered = sendFilteredMouseEvent(&e, item, item->parentItem());
+                    if (!filtered)
+                        item->mouseUngrabEvent();
+                }
+                if (point.device()->type() == QInputDevice::DeviceType::TouchScreen && event) {
+                    bool allReleased = true;
+                    for (const auto &pt : event->points()) {
+                        if (pt.state() != QEventPoint::State::Released) {
+                            allReleased = false;
+                            break;
+                        }
+                    }
+                    if (allReleased)
+                        item->touchUngrabEvent();
+                }
+            }
+            break;
+        default:
+            break;
+        }
     }
 }
 
@@ -2627,8 +2636,10 @@ void QQuickWindowPrivate::deliverPointerEvent(QPointerEvent *event)
         if (isTouchEvent(event)) {
             for (int i = 0; i < event->pointCount(); ++i) {
                 auto &point = event->point(i);
-                event->setExclusiveGrabber(point, nullptr);
-                event->clearPassiveGrabbers(point);
+                if (point.state() == QEventPoint::State::Released) {
+                    event->setExclusiveGrabber(point, nullptr);
+                    event->clearPassiveGrabbers(point);
+                }
             }
             // never allow touch->mouse synthesis to persist either
             cancelTouchMouseSynthesis();
diff --git a/src/quick/items/qquickwindow_p.h b/src/quick/items/qquickwindow_p.h
index 632cf1b6da..81c0ebef45 100644
--- a/src/quick/items/qquickwindow_p.h
+++ b/src/quick/items/qquickwindow_p.h
@@ -170,8 +170,7 @@ public:
     QPointF lastMousePosition;
     bool deliverTouchAsMouse(QQuickItem *item, QTouchEvent *pointerEvent);
     void translateTouchEvent(QTouchEvent *touchEvent);
-    void removeGrabber(QQuickItem *grabber, bool mouse = true, bool touch = true);
-    void sendUngrabEvent(QQuickItem *grabber, bool touch);
+    void removeGrabber(QQuickItem *grabber, bool mouse = true, bool touch = true, bool cancel = false);
     void onGrabChanged(QObject *grabber, QPointingDevice::GrabTransition transition, const QPointerEvent *event, const QEventPoint &point);
     static QMouseEvent *cloneMouseEvent(QMouseEvent *event, QPointF *transformedLocalPos = nullptr);
     void deliverToPassiveGrabbers(const QVector<QPointer<QObject> > &passiveGrabbers, QPointerEvent *pointerEvent);