Wrong QGraphicsItem::childrenBoundingRect() when applying effects.

Problem was that we used the children's raw bounding rect instead of
using their effective bounding rect when calculating the bounds.

Auto test included.

Task-number: QTBUG-10756

2 files changed, 32 insertions, 3 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index db6c4c513d..36d21a6238 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -1275,14 +1275,14 @@ void QGraphicsItemPrivate::childrenBoundingRectHelper(QTransform *x, QRectF *rec
             QTransform matrix = childd->transformToParent();
             if (x)
                 matrix *= *x;
-            *rect |= matrix.mapRect(child->boundingRect());
+            *rect |= matrix.mapRect(child->d_ptr->effectiveBoundingRect());
             if (!childd->children.isEmpty())
                 childd->childrenBoundingRectHelper(&matrix, rect);
         } else {
             if (x)
-                *rect |= x->mapRect(child->boundingRect());
+                *rect |= x->mapRect(child->d_ptr->effectiveBoundingRect());
             else
-                *rect |= child->boundingRect();
+                *rect |= child->d_ptr->effectiveBoundingRect();
             if (!childd->children.isEmpty())
                 childd->childrenBoundingRectHelper(x, rect);
         }
diff --git a/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp b/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp
index 300afc3ffe..5547b02820 100644
--- a/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp
+++ b/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp
@@ -348,6 +348,7 @@ private slots:
     void childrenBoundingRect2();
     void childrenBoundingRect3();
     void childrenBoundingRect4();
+    void childrenBoundingRect5();
     void group();
     void setGroup();
     void setGroup2();
@@ -3369,6 +3370,34 @@ void tst_QGraphicsItem::childrenBoundingRect4()
     QCOMPARE(rect2->childrenBoundingRect(), rect3->boundingRect());
 }
 
+void tst_QGraphicsItem::childrenBoundingRect5()
+{
+    QGraphicsScene scene;
+
+    QGraphicsRectItem *parent = scene.addRect(QRectF(0, 0, 100, 100));
+    QGraphicsRectItem *child = scene.addRect(QRectF(0, 0, 100, 100));
+    child->setParentItem(parent);
+
+    QGraphicsView view(&scene);
+    view.show();
+
+    QTest::qWaitForWindowShown(&view);
+
+    // Try to mess up the cached bounding rect.
+    QRectF expectedChildrenBoundingRect = parent->boundingRect();
+    QCOMPARE(parent->childrenBoundingRect(), expectedChildrenBoundingRect);
+
+    // Apply some effects.
+    QGraphicsDropShadowEffect *dropShadow = new QGraphicsDropShadowEffect;
+    dropShadow->setOffset(25, 25);
+    child->setGraphicsEffect(dropShadow);
+    parent->setGraphicsEffect(new QGraphicsOpacityEffect);
+
+    QVERIFY(parent->childrenBoundingRect() != expectedChildrenBoundingRect);
+    expectedChildrenBoundingRect |= dropShadow->boundingRect();
+    QCOMPARE(parent->childrenBoundingRect(), expectedChildrenBoundingRect);
+}
+
 void tst_QGraphicsItem::group()
 {
     QGraphicsScene scene;