Improved gesture event delivery in graphicsview.

Made it possible to delete a gesture target from a gesture event handler.  It
is still not possible to delete some items (like an item that originated the
gesture, i.e. that that the event that triggered the gesture to start), and in
that case deleteLater() should be used.

Reviewed-by: Andreas Aardal Hanssen

1 files changed, 198 insertions, 237 deletions

diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index 34543e3..40e1d2c 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -693,6 +693,18 @@ void QGraphicsScenePrivate::removeItemHelper(QGraphicsItem *item)
     --selectionChanging;
     if (!selectionChanging && selectedItems.size() != oldSelectedItemsSize)
         emit q->selectionChanged();
+
+    QHash<QGesture *, QGraphicsObject *>::iterator it;
+    for (it = gestureTargets.begin(); it != gestureTargets.end();) {
+        if (it.value() == item)
+            it = gestureTargets.erase(it);
+        else
+            ++it;
+    }
+    QGraphicsObject *dummy = static_cast<QGraphicsObject *>(item);
+    cachedTargetItems.removeOne(dummy);
+    cachedItemGestures.remove(dummy);
+    cachedAlreadyDeliveredGestures.remove(dummy);
 }
 
 /*!
@@ -5900,43 +5912,51 @@ void QGraphicsScenePrivate::leaveModal(QGraphicsItem *panel)
     dispatchHoverEvent(&hoverEvent);
 }
 
-void QGraphicsScenePrivate::getGestureTargets(const QSet<QGesture *> &gestures,
-                                              QMap<Qt::GestureType, QGesture *> *conflictedGestures,
-                                              QList<QList<QGraphicsObject *> > *conflictedItems,
-                                              QHash<QGesture *, QGraphicsObject *> *normalGestures)
+void QGraphicsScenePrivate::gestureTargetsAtHotSpots(const QSet<QGesture *> &gestures,
+                                              Qt::GestureFlag flag,
+                                              QHash<QGraphicsObject *, QSet<QGesture *> > *targets,
+                                              QSet<QGraphicsObject *> *itemsSet,
+                                              QSet<QGesture *> *normal,
+                                              QSet<QGesture *> *conflicts)
 {
+    QSet<QGesture *> normalGestures; // that are not in conflicted state.
     foreach (QGesture *gesture, gestures) {
-        Qt::GestureType gestureType = gesture->gestureType();
-        if (gesture->hasHotSpot()) {
-            QList<QGraphicsItem *> items = itemsAtPosition(QPoint(), gesture->d_func()->sceneHotSpot, 0);
-            QList<QGraphicsObject *> result;
-            for (int j = 0; j < items.size(); ++j) {
-                QGraphicsItem *item = items.at(j);
+        if (!gesture->hasHotSpot())
+            continue;
+        const Qt::GestureType gestureType = gesture->gestureType();
+        QList<QGraphicsItem *> items = itemsAtPosition(QPoint(), gesture->d_func()->sceneHotSpot, 0);
+        for (int j = 0; j < items.size(); ++j) {
+            QGraphicsItem *item = items.at(j);
 
-                // Check if the item is blocked by a modal panel and use it as
-                // a target instead of this item.
-                (void) item->isBlockedByModalPanel(&item);
+            // Check if the item is blocked by a modal panel and use it as
+            // a target instead of this item.
+            (void) item->isBlockedByModalPanel(&item);
 
-                if (QGraphicsObject *itemobj = item->toGraphicsObject()) {
-                    QGraphicsItemPrivate *d = item->d_func();
-                    if (d->gestureContext.contains(gestureType)) {
-                        result.append(itemobj);
+            if (QGraphicsObject *itemobj = item->toGraphicsObject()) {
+                QGraphicsItemPrivate *d = item->QGraphicsItem::d_func();
+                QMap<Qt::GestureType, Qt::GestureFlags>::const_iterator it =
+                        d->gestureContext.find(gestureType);
+                if (it != d->gestureContext.end() && (!flag || (it.value() & flag))) {
+                    if (normalGestures.contains(gesture)) {
+                        normalGestures.remove(gesture);
+                        if (conflicts)
+                            conflicts->insert(gesture);
+                    } else {
+                        normalGestures.insert(gesture);
                     }
+                    if (targets)
+                        (*targets)[itemobj].insert(gesture);
+                    if (itemsSet)
+                        (*itemsSet).insert(itemobj);
                 }
-                // Don't propagate through panels.
-                if (item->isPanel())
-                    break;
-            }
-            DEBUG() << "QGraphicsScenePrivate::getGestureTargets:"
-                    << gesture << result;
-            if (result.size() == 1) {
-                normalGestures->insert(gesture, result.first());
-            } else if (!result.isEmpty()) {
-                conflictedGestures->insert(gestureType, gesture);
-                conflictedItems->append(result);
             }
+            // Don't propagate through panels.
+            if (item->isPanel())
+                break;
         }
     }
+    if (normal)
+        *normal = normalGestures;
 }
 
 void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
@@ -5952,18 +5972,14 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
     DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
             << "Delivering gestures:" <<  allGestures;
 
-    typedef QHash<QGraphicsObject *, QList<QGesture *> > GesturesPerItem;
-    GesturesPerItem gesturesPerItem;
-
-    // gestures that are only supposed to propagate to parent items.
-    QSet<QGesture *> parentPropagatedGestures;
-
     QSet<QGesture *> startedGestures;
+    QPoint delta = graphicsView->mapFromGlobal(QPoint());
+    QTransform toScene =  QTransform::fromTranslate(delta.x(), delta.y())
+                          * graphicsView->viewportTransform().inverted();
     foreach (QGesture *gesture, allGestures) {
         // cache scene coordinates of the hot spot
         if (gesture->hasHotSpot()) {
-            gesture->d_func()->sceneHotSpot = graphicsView->mapToScene(
-                    graphicsView->mapFromGlobal(gesture->hotSpot().toPoint()));
+            gesture->d_func()->sceneHotSpot = toScene.map(gesture->hotSpot());
         } else {
             gesture->d_func()->sceneHotSpot = QPointF();
         }
@@ -5974,243 +5990,184 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
             // then the only one interested in gesture is the view/scene
             if (gesture->state() == Qt::GestureStarted)
                 startedGestures.insert(gesture);
-        } else {
-            gesturesPerItem[target].append(gesture);
-            Qt::GestureFlags flags =
-                    target->QGraphicsItem::d_func()->gestureContext.value(gesture->gestureType());
-            if (flags & Qt::IgnoredGesturesPropagateToParent)
-                parentPropagatedGestures.insert(gesture);
         }
     }
 
-    QMap<Qt::GestureType, QGesture *> conflictedGestures;
-    QList<QList<QGraphicsObject *> > conflictedItems;
-    QHash<QGesture *, QGraphicsObject *> normalGestures;
-    getGestureTargets(startedGestures, &conflictedGestures, &conflictedItems,
-                      &normalGestures);
-    DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
-            << "Conflicting gestures:" <<  conflictedGestures.values() << conflictedItems;
-    Q_ASSERT((conflictedGestures.isEmpty() && conflictedItems.isEmpty()) ||
-              (!conflictedGestures.isEmpty() && !conflictedItems.isEmpty()));
-
-    // gestures that were sent as override events, but no one accepted them
-    QHash<QGesture *, QGraphicsObject *> ignoredConflictedGestures;
-
-    // deliver conflicted gestures as override events first
-    while (!conflictedGestures.isEmpty() && !conflictedItems.isEmpty()) {
-        // get the topmost item to deliver the override event
-        Q_ASSERT(!conflictedItems.isEmpty());
-        Q_ASSERT(!conflictedItems.first().isEmpty());
-        QGraphicsObject *topmost = conflictedItems.first().first();
-        for (int i = 1; i < conflictedItems.size(); ++i) {
-            QGraphicsObject *item = conflictedItems.at(i).first();
-            if (qt_closestItemFirst(item, topmost)) {
-                topmost = item;
-            }
-        }
-        // get a list of gestures to send to the item
-        QList<Qt::GestureType> grabbedGestures =
-                topmost->QGraphicsItem::d_func()->gestureContext.keys();
-        QList<QGesture *> gestures;
-        for (int i = 0; i < grabbedGestures.size(); ++i) {
-            if (QGesture *g = conflictedGestures.value(grabbedGestures.at(i), 0)) {
-                gestures.append(g);
-                if (!ignoredConflictedGestures.contains(g))
-                    ignoredConflictedGestures.insert(g, topmost);
-            }
-        }
-
-        // send gesture override to the topmost item
-        QGestureEvent ev(gestures);
-        ev.t = QEvent::GestureOverride;
-        ev.setWidget(event->widget());
-        // mark event and individual gestures as ignored
-        ev.ignore();
-        foreach(QGesture *g, gestures)
-            ev.setAccepted(g, false);
+    if (!startedGestures.isEmpty()) {
+        QSet<QGesture *> normalGestures; // that have just one target
+        QSet<QGesture *> conflictedGestures; // that have multiple possible targets
+        gestureTargetsAtHotSpots(startedGestures, Qt::GestureFlag(0), &cachedItemGestures, 0,
+                                 &normalGestures, &conflictedGestures);
+        cachedTargetItems = cachedItemGestures.keys();
+        qSort(cachedTargetItems.begin(), cachedTargetItems.end(), qt_closestItemFirst);
         DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
-                << "delivering override to"
-                << topmost << gestures;
-        sendEvent(topmost, &ev);
-        // mark all accepted gestures to deliver them as normal gesture events
-        foreach (QGesture *g, gestures) {
-            if (ev.isAccepted() || ev.isAccepted(g)) {
-                conflictedGestures.remove(g->gestureType());
-                gestureTargets.remove(g);
-                // add the gesture to the list of normal delivered gestures
-                normalGestures.insert(g, topmost);
+                << "Conflicting gestures:" <<  conflictedGestures;
+
+        // deliver conflicted gestures as override events AND remember
+        // initial gesture targets
+        if (!conflictedGestures.isEmpty()) {
+            for (int i = 0; i < cachedTargetItems.size(); ++i) {
+                QWeakPointer<QGraphicsObject> item = cachedTargetItems.at(i);
+
+                // get gestures to deliver to the current item
+                QSet<QGesture *> gestures = conflictedGestures & cachedItemGestures.value(item.data());
+                if (gestures.isEmpty())
+                    continue;
+
                 DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
-                        << "override was accepted:"
-                        << g << topmost;
-                ignoredConflictedGestures.remove(g);
+                        << "delivering override to"
+                        << item.data() << gestures;
+                // send gesture override
+                QGestureEvent ev(gestures.toList());
+                ev.t = QEvent::GestureOverride;
+                ev.setWidget(event->widget());
+                // mark event and individual gestures as ignored
+                ev.ignore();
+                foreach(QGesture *g, gestures)
+                    ev.setAccepted(g, false);
+                sendEvent(item.data(), &ev);
+                // mark all accepted gestures to deliver them as normal gesture events
+                foreach (QGesture *g, gestures) {
+                    if (ev.isAccepted() || ev.isAccepted(g)) {
+                        conflictedGestures.remove(g);
+                        // mark the item as a gesture target
+                        if (item)
+                            gestureTargets.insert(g, item.data());
+                        DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
+                                << "override was accepted:"
+                                << g << item.data();
+                    }
+                    // remember the first item that received the override event
+                    // as it most likely become a target if noone else accepts
+                    // the override event
+                    if (!gestureTargets.contains(g) && item)
+                        gestureTargets.insert(g, item.data());
+
+                }
+                if (conflictedGestures.isEmpty())
+                    break;
             }
         }
-        // remove the item that we've already delivered from the list
-        for (int i = 0; i < conflictedItems.size(); ) {
-            QList<QGraphicsObject *> &items = conflictedItems[i];
-            if (items.first() == topmost) {
-                items.removeFirst();
-                if (items.isEmpty()) {
-                    conflictedItems.removeAt(i);
-                    continue;
+        // remember the initial target item for each gesture that was not in
+        // the conflicted state.
+        if (!normalGestures.isEmpty()) {
+            for (int i = 0; i < cachedTargetItems.size() && !normalGestures.isEmpty(); ++i) {
+                QGraphicsObject *item = cachedTargetItems.at(i);
+
+                // get gestures to deliver to the current item
+                foreach (QGesture *g, cachedItemGestures.value(item)) {
+                    if (!gestureTargets.contains(g)) {
+                        gestureTargets.insert(g, item);
+                        normalGestures.remove(g);
+                    }
                 }
             }
-            ++i;
         }
     }
 
-    // put back those started gestures that are not in the conflicted state
-    // and remember their targets
-    QHash<QGesture *, QGraphicsObject *>::const_iterator it = normalGestures.begin(),
-                                                          e = normalGestures.end();
-    for (; it != e; ++it) {
-        QGesture *g = it.key();
-        QGraphicsObject *receiver = it.value();
-        Q_ASSERT(!gestureTargets.contains(g));
-        gestureTargets.insert(g, receiver);
-        gesturesPerItem[receiver].append(g);
-        Qt::GestureFlags flags =
-                receiver->QGraphicsItem::d_func()->gestureContext.value(g->gestureType());
-        if (flags & Qt::IgnoredGesturesPropagateToParent)
-            parentPropagatedGestures.insert(g);
-    }
-    it = ignoredConflictedGestures.begin();
-    e = ignoredConflictedGestures.end();
-    for (; it != e; ++it) {
-        QGesture *g = it.key();
-        QGraphicsObject *receiver = it.value();
-        Q_ASSERT(!gestureTargets.contains(g));
-        gestureTargets.insert(g, receiver);
-        gesturesPerItem[receiver].append(g);
-        Qt::GestureFlags flags =
-                receiver->QGraphicsItem::d_func()->gestureContext.value(g->gestureType());
-        if (flags & Qt::IgnoredGesturesPropagateToParent)
-            parentPropagatedGestures.insert(g);
-    }
-
-    DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
-            << "Started gestures:" << normalGestures.keys()
-            << "All gestures:" << gesturesPerItem.values();
 
     // deliver all gesture events
-    QList<QGesture *> alreadyIgnoredGestures;
-    QHash<QGraphicsObject *, QSet<QGesture *> > itemIgnoredGestures;
-    QList<QGraphicsObject *> targetItems = gesturesPerItem.keys();
-    qSort(targetItems.begin(), targetItems.end(), qt_closestItemFirst);
-    for (int i = 0; i < targetItems.size(); ++i) {
-        QGraphicsObject *item = targetItems.at(i);
-        QList<QGesture *> gestures = gesturesPerItem.value(item);
-        // remove gestures that were already delivered once and were ignored
-        DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
-                << "already ignored gestures for item"
-                << item << ":" << itemIgnoredGestures.value(item);
-
-        if (itemIgnoredGestures.contains(item)) // don't deliver twice to the same item
-            continue;
-
-        QGraphicsItemPrivate *gid = item->QGraphicsItem::d_func();
-        foreach(QGesture *g, alreadyIgnoredGestures) {
-            QMap<Qt::GestureType, Qt::GestureFlags>::iterator contextit =
-                    gid->gestureContext.find(g->gestureType());
-            bool deliver = false;
-            if (contextit != gid->gestureContext.end()) {
-                if (g->state() == Qt::GestureStarted) {
-                    deliver = true;
-                } else {
-                    const Qt::GestureFlags flags = contextit.value();
-                    if (flags & Qt::ReceivePartialGestures) {
-                        QGraphicsObject *originalTarget = gestureTargets.value(g);
-                        Q_ASSERT(originalTarget);
-                        QGraphicsItemPrivate *otd = originalTarget->QGraphicsItem::d_func();
-                        const Qt::GestureFlags originalTargetFlags = otd->gestureContext.value(g->gestureType());
-                        if (originalTargetFlags & Qt::IgnoredGesturesPropagateToParent) {
-                            // only deliver to parents of the original target item
-                            deliver = item->isAncestorOf(originalTarget);
-                        } else {
-                            deliver = true;
-                        }
-                    }
-                }
-            }
-            if (deliver)
-                gestures += g;
+    QSet<QGesture *> undeliveredGestures;
+    QSet<QGesture *> parentPropagatedGestures;
+    foreach (QGesture *gesture, allGestures) {
+        if (QGraphicsObject *target = gestureTargets.value(gesture, 0)) {
+            cachedItemGestures[target].insert(gesture);
+            cachedTargetItems.append(target);
+            undeliveredGestures.insert(gesture);
+            QGraphicsItemPrivate *d = target->QGraphicsItem::d_func();
+            const Qt::GestureFlags flags = d->gestureContext.value(gesture->gestureType());
+            if (flags & Qt::IgnoredGesturesPropagateToParent)
+                parentPropagatedGestures.insert(gesture);
         }
+    }
+    qSort(cachedTargetItems.begin(), cachedTargetItems.end(), qt_closestItemFirst);
+    for (int i = 0; i < cachedTargetItems.size(); ++i) {
+        QWeakPointer<QGraphicsObject> receiver = cachedTargetItems.at(i);
+        QSet<QGesture *> gestures =
+                undeliveredGestures & cachedItemGestures.value(receiver.data());
+        gestures -= cachedAlreadyDeliveredGestures.value(receiver.data());
+
         if (gestures.isEmpty())
             continue;
+
+        cachedAlreadyDeliveredGestures[receiver.data()] += gestures;
+        const bool isPanel = receiver.data()->isPanel();
+
         DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
                 << "delivering to"
-                << item << gestures;
-        QGestureEvent ev(gestures);
+                << receiver.data() << gestures;
+        QGestureEvent ev(gestures.toList());
         ev.setWidget(event->widget());
-        sendEvent(item, &ev);
+        sendEvent(receiver.data(), &ev);
         QSet<QGesture *> ignoredGestures;
         foreach (QGesture *g, gestures) {
             if (!ev.isAccepted() && !ev.isAccepted(g)) {
-                ignoredGestures.insert(g);
+                // if the gesture was ignored by its target, we will update the
+                // targetItems list with a possible target items (items that
+                // want to receive partial gestures).
+                // ### wont' work if the target was destroyed in the event
+                //     we will just stop delivering it.
+                if (receiver && receiver.data() == gestureTargets.value(g, 0))
+                    ignoredGestures.insert(g);
             } else {
-                if (g->state() == Qt::GestureStarted)
-                    gestureTargets[g] = item;
-            }
-        }
-        if (!ignoredGestures.isEmpty()) {
-            // get a list of items under the (current) hotspot of each ignored
-            // gesture and start delivery again from the beginning
-            DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
-                    << "item has ignored the event, will propagate."
-                    << item << ignoredGestures;
-            itemIgnoredGestures[item] += ignoredGestures;
-            alreadyIgnoredGestures = ignoredGestures.toList();
-
-            // remove gestures that are supposed to be propagated to
-            // parent items only.
-            QSet<QGesture *> parentGestures;
-            for (QSet<QGesture *>::iterator it = ignoredGestures.begin();
-                 it != ignoredGestures.end();) {
-                if (parentPropagatedGestures.contains(*it)) {
-                    parentGestures.insert(*it);
-                    it = ignoredGestures.erase(it);
-                } else {
-                    ++it;
+                if (receiver && g->state() == Qt::GestureStarted) {
+                    // someone accepted the propagated initial GestureStarted
+                    // event, let it be the new target for all following events.
+                    gestureTargets[g] = receiver.data();
                 }
+                undeliveredGestures.remove(g);
             }
+        }
+        if (undeliveredGestures.isEmpty())
+            break;
+
+        // ignoredGestures list is only filled when delivering to the gesture
+        // target item, so it is safe to assume item == target.
+        if (!ignoredGestures.isEmpty() && !isPanel) {
+            // look for new potential targets for gestures that were ignored
+            // and should be propagated.
+
+            QSet<QGraphicsObject *> targetsSet = cachedTargetItems.toSet();
+
+            if (receiver) {
+                // first if the gesture should be propagated to parents only
+                for (QSet<QGesture *>::iterator it = ignoredGestures.begin();
+                     it != ignoredGestures.end();) {
+                    if (parentPropagatedGestures.contains(*it)) {
+                        QGesture *gesture = *it;
+                        const Qt::GestureType gestureType = gesture->gestureType();
+                        QGraphicsItem *item = receiver.data();
+                        while (item) {
+                            if (QGraphicsObject *obj = item->toGraphicsObject()) {
+                                if (item->d_func()->gestureContext.contains(gestureType)) {
+                                    targetsSet.insert(obj);
+                                    cachedItemGestures[obj].insert(gesture);
+                                }
+                            }
+                            if (item->isPanel())
+                                break;
+                            item = item->parentItem();
+                        }
 
-            QSet<QGraphicsObject *> itemsSet = targetItems.toSet();
-
-            foreach(QGesture *g, parentGestures) {
-                // get the original target for the gesture
-                QGraphicsItem *item = gestureTargets.value(g, 0);
-                Q_ASSERT(item);
-                const Qt::GestureType gestureType = g->gestureType();
-                // iterate through parent items of the original gesture
-                // target item and collect potential receivers
-                do {
-                    if (QGraphicsObject *obj = item->toGraphicsObject()) {
-                        if (item->d_func()->gestureContext.contains(gestureType))
-                            itemsSet.insert(obj);
+                        it = ignoredGestures.erase(it);
+                        continue;
                     }
-                    if (item->isPanel())
-                        break;
-                } while ((item = item->parentItem()));
+                    ++it;
+                }
             }
 
-            QMap<Qt::GestureType, QGesture *> conflictedGestures;
-            QList<QList<QGraphicsObject *> > itemsForConflictedGestures;
-            QHash<QGesture *, QGraphicsObject *> normalGestures;
-            getGestureTargets(ignoredGestures,
-                              &conflictedGestures, &itemsForConflictedGestures,
-                              &normalGestures);
-            for (int k = 0; k < itemsForConflictedGestures.size(); ++k)
-                itemsSet += itemsForConflictedGestures.at(k).toSet();
-
-            targetItems = itemsSet.toList();
+            gestureTargetsAtHotSpots(ignoredGestures, Qt::ReceivePartialGestures,
+                                     &cachedItemGestures, &targetsSet, 0, 0);
 
-            qSort(targetItems.begin(), targetItems.end(), qt_closestItemFirst);
+            cachedTargetItems = targetsSet.toList();
+            qSort(cachedTargetItems.begin(), cachedTargetItems.end(), qt_closestItemFirst);
             DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
-                    << "new targets:" << targetItems;
+                    << "new targets:" << cachedTargetItems;
             i = -1; // start delivery again
             continue;
         }
     }
+
     foreach (QGesture *g, startedGestures) {
         if (g->gestureCancelPolicy() == QGesture::CancelAllInContext) {
             DEBUG() << "lets try to cancel some";
@@ -6230,6 +6187,10 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
             break;
         }
     }
+
+    cachedTargetItems.clear();
+    cachedItemGestures.clear();
+    cachedAlreadyDeliveredGestures.clear();
 }
 
 void QGraphicsScenePrivate::cancelGesturesForChildren(QGesture *original)