Added a new flag to fine-tune gesture propagation policy

When a graphicsobject subscribes to a gesture using the
IgnoredGesturesPropagateToParent flag, normal propagation rules do not apply to
the gesture, and instead all gestures of the given type that are started over
the item will propagate to parent items only.

Task-number: QTBUG-7400
Reviewed-by: Andreas

1 files changed, 72 insertions, 6 deletions

diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index 9a36d46..3280e86 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -5936,6 +5936,9 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
     typedef QHash<QGraphicsObject *, QList<QGesture *> > GesturesPerItem;
     GesturesPerItem gesturesPerItem;
 
+    // gestures that are only supposed to propagate to parent items.
+    QSet<QGesture *> parentPropagatedGestures;
+
     QSet<QGesture *> startedGestures;
     foreach (QGesture *gesture, allGestures) {
         QGraphicsObject *target = gestureTargets.value(gesture, 0);
@@ -5946,6 +5949,10 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
                 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);
         }
     }
 
@@ -6035,6 +6042,10 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
         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();
@@ -6044,13 +6055,17 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
         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 events
+    // deliver all gesture events
     QList<QGesture *> alreadyIgnoredGestures;
     QHash<QGraphicsObject *, QSet<QGesture *> > itemIgnoredGestures;
     QList<QGraphicsObject *> targetItems = gesturesPerItem.keys();
@@ -6070,9 +6085,26 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
         foreach(QGesture *g, alreadyIgnoredGestures) {
             QMap<Qt::GestureType, Qt::GestureFlags>::iterator contextit =
                     gid->gestureContext.find(g->gestureType());
-            bool deliver = contextit != gid->gestureContext.end() &&
-                (g->state() == Qt::GestureStarted ||
-                 (contextit.value() & Qt::ReceivePartialGestures));
+            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;
         }
@@ -6100,18 +6132,52 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
                     << "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;
+                }
+            }
+
+            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);
+                    }
+                    if (item->isPanel())
+                        break;
+                } while ((item = item->parentItem()));
+            }
+
             QMap<Qt::GestureType, QGesture *> conflictedGestures;
             QList<QList<QGraphicsObject *> > itemsForConflictedGestures;
             QHash<QGesture *, QGraphicsObject *> normalGestures;
             getGestureTargets(ignoredGestures, viewport,
                               &conflictedGestures, &itemsForConflictedGestures,
                               &normalGestures);
-            QSet<QGraphicsObject *> itemsSet = targetItems.toSet();
             for (int k = 0; k < itemsForConflictedGestures.size(); ++k)
                 itemsSet += itemsForConflictedGestures.at(k).toSet();
+
             targetItems = itemsSet.toList();
+
             qSort(targetItems.begin(), targetItems.end(), qt_closestItemFirst);
-            alreadyIgnoredGestures = conflictedGestures.values();
             DEBUG() << "QGraphicsScenePrivate::gestureEventHandler:"
                     << "new targets:" << targetItems;
             i = -1; // start delivery again