2 files changed, 19 insertions, 1 deletions
diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index b9e462b..e09d3f0 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -925,6 +925,11 @@ void QGraphicsItemPrivate::setParentItemHelper(QGraphicsItem *newParent, bool de
 */
 void QGraphicsItemPrivate::childrenBoundingRectHelper(QTransform *x, QRectF *rect)
 {
+    if (!dirtyChildrenBoundingRect) {
+        *rect |= x->mapRect(childrenBoundingRect);
+        return;
+    }
+
     for (int i = 0; i < children.size(); ++i) {
         QGraphicsItem *child = children.at(i);
         QGraphicsItemPrivate *childd = child->d_ptr;
@@ -948,6 +953,9 @@ void QGraphicsItemPrivate::childrenBoundingRectHelper(QTransform *x, QRectF *rec
                 childd->childrenBoundingRectHelper(x, rect);
         }
     }
+
+    childrenBoundingRect = *rect;
+    dirtyChildrenBoundingRect = 0;
 }
 
 void QGraphicsItemPrivate::initStyleOption(QStyleOptionGraphicsItem *option, const QTransform &worldTransform,
@@ -3567,6 +3575,9 @@ void QGraphicsItem::setZValue(qreal z)
 */
 QRectF QGraphicsItem::childrenBoundingRect() const
 {
+    if (!d_ptr->dirtyChildrenBoundingRect)
+        return d_ptr->childrenBoundingRect;
+
     QRectF childRect;
     QTransform x;
     d_ptr->childrenBoundingRectHelper(&x, &childRect);
@@ -6400,6 +6411,10 @@ void QGraphicsItem::prepareGeometryChange()
         scenePrivate->removeFromIndex(this);
     }
 
+    QGraphicsItem *parent = this;
+    while (parent = parent->d_ptr->parent)
+        parent->d_ptr->dirtyChildrenBoundingRect = 1;
+
     if (d_ptr->inSetPosHelper)
         return;
 
diff --git a/src/gui/graphicsview/qgraphicsitem_p.h b/src/gui/graphicsview/qgraphicsitem_p.h
index bd81fe5..200d177 100644
--- a/src/gui/graphicsview/qgraphicsitem_p.h
+++ b/src/gui/graphicsview/qgraphicsitem_p.h
@@ -160,6 +160,7 @@ public:
         hasDecomposedTransform(0),
         dirtyTransform(0),
         dirtyTransformComponents(0),
+        dirtyChildrenBoundingRect(1),
         globalStackingOrder(-1),
         sceneTransformIndex(-1),
         q_ptr(0)
@@ -308,6 +309,7 @@ public:
     }
 
     QPainterPath cachedClipPath;
+    QRectF childrenBoundingRect;
     QPointF pos;
     qreal z;
     QGraphicsScene *scene;
@@ -350,7 +352,8 @@ public:
     quint32 hasDecomposedTransform : 1;
     quint32 dirtyTransform : 1;
     quint32 dirtyTransformComponents : 1;
-    quint32 padding : 18; // feel free to use
+    quint32 dirtyChildrenBoundingRect : 1;
+    quint32 padding : 17; // feel free to use
 
     // Optional stacking order
     int globalStackingOrder;