Introduced QGraphicsItem::ItemSendsScenePositionChanges and

QGraphicsItem::ItemScenePositionHasChanged

Merge-Request: 1945
Reviewed-By: Andreas

6 files changed, 132 insertions, 8 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index 4665916..93b9ba9 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -386,6 +386,12 @@
     introduced in Qt 4.6.
 
     \omitvalue ItemIsFocusScope Internal only (for now).
+
+    \value ItemSendsScenePositionChanges The item enables itemChange()
+    notifications for ItemScenePositionHasChanged. For performance reasons,
+    these notifications are disabled by default. You must enable this flag
+    to receive notifications for scene position changes. This flag was
+    introduced in Qt 4.6.
 */
 
 /*!
@@ -562,6 +568,14 @@
     \value ItemOpacityHasChanged The item's opacity has changed. The value
     argument is the new opacity (i.e., a double). Do not call setOpacity() as
     this notification is delivered. The return value is ignored.
+
+    \value ItemScenePositionHasChanged The item's scene position has changed.
+    This notification is sent if the ItemSendsScenePositionChanges flag is
+    enabled, and after the item's scene position has changed (i.e., the
+    position or transformation of the item itself or the position or
+    transformation of any ancestor has changed). The value argument is the
+    new scene position (the same as scenePos()), and QGraphicsItem ignores
+    the return value for this notification (i.e., a read-only notification).
 */
 
 /*!
@@ -990,6 +1004,10 @@ void QGraphicsItemPrivate::setParentItemHelper(QGraphicsItem *newParent)
     if (scene) {
         // Deliver the change to the index
         scene->d_func()->index->itemChange(q, QGraphicsItem::ItemParentChange, newParentVariant);
+
+        // Disable scene pos notifications for old ancestors
+        if (scenePosDescendants || (flags & QGraphicsItem::ItemSendsScenePositionChanges))
+            scene->d_func()->setScenePosItemEnabled(q, false);
     }
 
     if (subFocusItem && parent) {
@@ -1084,10 +1102,15 @@ void QGraphicsItemPrivate::setParentItemHelper(QGraphicsItem *newParent)
 
         parent->d_ptr->addChild(q);
         parent->itemChange(QGraphicsItem::ItemChildAddedChange, thisPointerVariant);
-        if (!implicitUpdate && scene) {
-            scene->d_func()->markDirty(q_ptr, QRect(),
-                                       /*invalidateChildren=*/false,
-                                       /*maybeDirtyClipPath=*/true);
+        if (scene) {
+            if (!implicitUpdate)
+                scene->d_func()->markDirty(q_ptr, QRect(),
+                                           /*invalidateChildren=*/false,
+                                           /*maybeDirtyClipPath=*/true);
+
+            // Re-enable scene pos notifications for new ancestors
+            if (scenePosDescendants || (flags & QGraphicsItem::ItemSendsScenePositionChanges))
+                scene->d_func()->setScenePosItemEnabled(q, true);
         }
 
         // Inherit ancestor flags from the new parent.
@@ -1746,6 +1769,12 @@ void QGraphicsItem::setFlags(GraphicsItemFlags flags)
     }
 
     if (d_ptr->scene) {
+        if ((flags & ItemSendsScenePositionChanges) != (oldFlags & ItemSendsScenePositionChanges)) {
+            if (flags & ItemSendsScenePositionChanges)
+                d_ptr->scene->d_func()->registerScenePosItem(this);
+            else
+                d_ptr->scene->d_func()->unregisterScenePosItem(this);
+        }
         d_ptr->scene->d_func()->markDirty(this, QRectF(),
                                           /*invalidateChildren=*/true,
                                           /*maybeDirtyClipPath*/true);
@@ -3412,6 +3441,7 @@ void QGraphicsItem::setPos(const QPointF &pos)
 
     // Send post-notification.
     itemChange(QGraphicsItem::ItemPositionHasChanged, newPosVariant);
+    d_ptr->sendScenePosChange();
 }
 
 /*!
@@ -4022,6 +4052,7 @@ void QGraphicsItem::setTransform(const QTransform &matrix, bool combine)
 
     // Send post-notification.
     itemChange(ItemTransformHasChanged, newTransformVariant);
+    d_ptr->sendScenePosChange();
 }
 
 /*!
@@ -4246,6 +4277,24 @@ void QGraphicsItemPrivate::ensureSequentialSiblingIndex()
 }
 
 /*!
+    \internal
+*/
+inline void QGraphicsItemPrivate::sendScenePosChange()
+{
+    Q_Q(QGraphicsItem);
+    if (scene) {
+        if (flags & QGraphicsItem::ItemSendsScenePositionChanges)
+            q->itemChange(QGraphicsItem::ItemScenePositionHasChanged, q->scenePos());
+        if (scenePosDescendants) {
+            foreach (QGraphicsItem *item, scene->d_func()->scenePosItems) {
+                if (q->isAncestorOf(item))
+                    item->itemChange(QGraphicsItem::ItemScenePositionHasChanged, item->scenePos());
+            }
+        }
+    }
+}
+
+/*!
     \since 4.6
 
     Stacks this item before \a sibling, which must be a sibling item (i.e., the
@@ -10925,6 +10974,9 @@ QDebug operator<<(QDebug debug, QGraphicsItem::GraphicsItemChange change)
     case QGraphicsItem::ItemOpacityHasChanged:
         str = "ItemOpacityHasChanged";
         break;
+    case QGraphicsItem::ItemScenePositionHasChanged:
+        str = "ItemScenePositionHasChanged";
+        break;
     }
     debug << str;
     return debug;
@@ -10982,6 +11034,9 @@ QDebug operator<<(QDebug debug, QGraphicsItem::GraphicsItemFlag flag)
     case QGraphicsItem::ItemIsFocusScope:
         str = "ItemIsFocusScope";
         break;
+    case QGraphicsItem::ItemSendsScenePositionChanges:
+        str = "ItemSendsScenePositionChanges";
+        break;
     }
     debug << str;
     return debug;
diff --git a/src/gui/graphicsview/qgraphicsitem.h b/src/gui/graphicsview/qgraphicsitem.h
index f3fe99c..6e1c632 100644
--- a/src/gui/graphicsview/qgraphicsitem.h
+++ b/src/gui/graphicsview/qgraphicsitem.h
@@ -105,7 +105,8 @@ public:
         ItemAcceptsInputMethod = 0x1000,
         ItemNegativeZStacksBehindParent = 0x2000,
         ItemIsPanel = 0x4000,
-        ItemIsFocusScope = 0x8000 // internal
+        ItemIsFocusScope = 0x8000, // internal
+        ItemSendsScenePositionChanges = 0x10000
         // NB! Don't forget to increase the d_ptr->flags bit field by 1 when adding a new flag.
     };
     Q_DECLARE_FLAGS(GraphicsItemFlags, GraphicsItemFlag)
@@ -137,7 +138,8 @@ public:
         ItemZValueChange,
         ItemZValueHasChanged,
         ItemOpacityChange,
-        ItemOpacityHasChanged
+        ItemOpacityHasChanged,
+        ItemScenePositionHasChanged
     };
 
     enum CacheMode {
diff --git a/src/gui/graphicsview/qgraphicsitem_p.h b/src/gui/graphicsview/qgraphicsitem_p.h
index ca56c18..92d45f6 100644
--- a/src/gui/graphicsview/qgraphicsitem_p.h
+++ b/src/gui/graphicsview/qgraphicsitem_p.h
@@ -179,6 +179,7 @@ public:
         holesInSiblingIndex(0),
         sequentialOrdering(1),
         updateDueToGraphicsEffect(0),
+        scenePosDescendants(0),
         globalStackingOrder(-1),
         q_ptr(0)
     {
@@ -429,6 +430,7 @@ public:
     inline void ensureSortedChildren();
     static inline bool insertionOrder(QGraphicsItem *a, QGraphicsItem *b);
     void ensureSequentialSiblingIndex();
+    inline void sendScenePosChange();
 
     QPainterPath cachedClipPath;
     QRectF childrenBoundingRect;
@@ -483,7 +485,7 @@ public:
 
     // Packed 32 bits
     quint32 fullUpdatePending : 1;
-    quint32 flags : 16;
+    quint32 flags : 17;
     quint32 dirtyChildrenBoundingRect : 1;
     quint32 paintedViewBoundingRectsNeedRepaint : 1;
     quint32 dirtySceneTransform : 1;
@@ -498,14 +500,15 @@ public:
     quint32 sceneTransformTranslateOnly : 1;
     quint32 notifyBoundingRectChanged : 1;
     quint32 notifyInvalidated : 1;
-    quint32 mouseSetsFocus : 1;
 
     // New 32 bits
+    quint32 mouseSetsFocus : 1;
     quint32 explicitActivate : 1;
     quint32 wantsActive : 1;
     quint32 holesInSiblingIndex : 1;
     quint32 sequentialOrdering : 1;
     quint32 updateDueToGraphicsEffect : 1;
+    quint32 scenePosDescendants : 1;
 
     // Optional stacking order
     int globalStackingOrder;
diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index a4965e4..b992398 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -294,6 +294,7 @@ QGraphicsScenePrivate::QGraphicsScenePrivate()
       needSortTopLevelItems(true),
       holesInTopLevelSiblingIndex(false),
       topLevelSequentialOrdering(true),
+      scenePosDescendantsUpdatePending(false),
       stickyFocus(false),
       hasFocus(false),
       focusItem(0),
@@ -488,6 +489,55 @@ void QGraphicsScenePrivate::_q_processDirtyItems()
 
 /*!
     \internal
+*/
+void QGraphicsScenePrivate::setScenePosItemEnabled(QGraphicsItem *item, bool enabled)
+{
+    QGraphicsItem *p = item->d_ptr->parent;
+    while (p) {
+        p->d_ptr->scenePosDescendants = enabled;
+        p = p->d_ptr->parent;
+    }
+    if (!enabled && !scenePosDescendantsUpdatePending) {
+        scenePosDescendantsUpdatePending = true;
+        QMetaObject::invokeMethod(q_func(), "_q_updateScenePosDescendants", Qt::QueuedConnection);
+    }
+}
+
+/*!
+    \internal
+*/
+void QGraphicsScenePrivate::registerScenePosItem(QGraphicsItem *item)
+{
+    scenePosItems.insert(item);
+    setScenePosItemEnabled(item, true);
+}
+
+/*!
+    \internal
+*/
+void QGraphicsScenePrivate::unregisterScenePosItem(QGraphicsItem *item)
+{
+    scenePosItems.remove(item);
+    setScenePosItemEnabled(item, false);
+}
+
+/*!
+    \internal
+*/
+void QGraphicsScenePrivate::_q_updateScenePosDescendants()
+{
+    foreach (QGraphicsItem *item, scenePosItems) {
+        QGraphicsItem *p = item->d_ptr->parent;
+        while (p) {
+            p->d_ptr->scenePosDescendants = 1;
+            p = p->d_ptr->parent;
+        }
+    }
+    scenePosDescendantsUpdatePending = false;
+}
+
+/*!
+    \internal
 
     Schedules an item for removal. This function leaves some stale indexes
     around in the BSP tree if called from the item's destructor; these will
@@ -523,6 +573,9 @@ void QGraphicsScenePrivate::removeItemHelper(QGraphicsItem *item)
         widget->d_func()->fixFocusChainBeforeReparenting(0, 0);
     }
 
+    if (item->flags() & QGraphicsItem::ItemSendsScenePositionChanges)
+        unregisterScenePosItem(item);
+
     item->d_func()->scene = 0;
 
     //We need to remove all children first because they might use their parent
@@ -2540,6 +2593,9 @@ void QGraphicsScene::addItem(QGraphicsItem *item)
         }
     }
 
+    if (item->flags() & QGraphicsItem::ItemSendsScenePositionChanges)
+        d->registerScenePosItem(item);
+
     // Ensure that newly added items that have subfocus set, gain
     // focus automatically if there isn't a focus item already.
     if (!d->focusItem && item != d->lastFocusItem && item->focusItem() == item)
diff --git a/src/gui/graphicsview/qgraphicsscene.h b/src/gui/graphicsview/qgraphicsscene.h
index d6d48d7..a47574e 100644
--- a/src/gui/graphicsview/qgraphicsscene.h
+++ b/src/gui/graphicsview/qgraphicsscene.h
@@ -299,6 +299,7 @@ private:
     Q_PRIVATE_SLOT(d_func(), void _q_emitUpdated())
     Q_PRIVATE_SLOT(d_func(), void _q_polishItems())
     Q_PRIVATE_SLOT(d_func(), void _q_processDirtyItems())
+    Q_PRIVATE_SLOT(d_func(), void _q_updateScenePosDescendants())
     friend class QGraphicsItem;
     friend class QGraphicsItemPrivate;
     friend class QGraphicsView;
diff --git a/src/gui/graphicsview/qgraphicsscene_p.h b/src/gui/graphicsview/qgraphicsscene_p.h
index cd20fd0..6d46db5 100644
--- a/src/gui/graphicsview/qgraphicsscene_p.h
+++ b/src/gui/graphicsview/qgraphicsscene_p.h
@@ -122,6 +122,13 @@ public:
 
     void _q_processDirtyItems();
 
+    QSet<QGraphicsItem *> scenePosItems;
+    bool scenePosDescendantsUpdatePending;
+    void setScenePosItemEnabled(QGraphicsItem *item, bool enabled);
+    void registerScenePosItem(QGraphicsItem *item);
+    void unregisterScenePosItem(QGraphicsItem *item);
+    void _q_updateScenePosDescendants();
+
     void removeItemHelper(QGraphicsItem *item);
 
     QBrush backgroundBrush;