Fixes broken BSP lookup in QGraphicsSceneBspTreeIndex.

The chip demo was unbelievable slow, so I investigated and found out
the bsp always returned almost all items in the tree (40 000 in this
particular case). It did so because the tree was initialized with
an empty sceneRect. The sceneRect was empty due to a lacking signal-slot
connection, resulting in QGraphicsSceneBspTreeIndex::updateSceneRect
never being invoked.

Auto-test included.

3 files changed, 27 insertions, 6 deletions

diff --git a/src/gui/graphicsview/qgraphicssceneindex.cpp b/src/gui/graphicsview/qgraphicssceneindex.cpp
index 2f2f05e..b317e8e 100644
--- a/src/gui/graphicsview/qgraphicssceneindex.cpp
+++ b/src/gui/graphicsview/qgraphicssceneindex.cpp
@@ -303,24 +303,31 @@ void QGraphicsSceneIndexPrivate::recursive_items_helper(QGraphicsItem *item, QRe
     }
 }
 
+void QGraphicsSceneIndexPrivate::init()
+{
+    if (!scene)
+        return;
+
+    QObject::connect(scene, SIGNAL(sceneRectChanged(const QRectF&)),
+                     q_func(), SLOT(updateSceneRect(const QRectF&)));
+}
+
 /*!
     Constructs an abstract scene index for a given \a scene.
 */
 QGraphicsSceneIndex::QGraphicsSceneIndex(QGraphicsScene *scene)
 : QObject(*new QGraphicsSceneIndexPrivate(scene), scene)
 {
-    if (scene) {
-        connect(scene, SIGNAL(sceneRectChanged(const QRectF&)),
-                this, SLOT(updateSceneRect(const QRectF&)));
-    }
+    d_func()->init();
 }
 
 /*!
     \internal
 */
-QGraphicsSceneIndex::QGraphicsSceneIndex(QObjectPrivate &dd, QGraphicsScene *scene)
+QGraphicsSceneIndex::QGraphicsSceneIndex(QGraphicsSceneIndexPrivate &dd, QGraphicsScene *scene)
     : QObject(dd, scene)
 {
+    d_func()->init();
 }
 
 /*!
diff --git a/src/gui/graphicsview/qgraphicssceneindex_p.h b/src/gui/graphicsview/qgraphicssceneindex_p.h
index 122d7ae..aabfa79 100644
--- a/src/gui/graphicsview/qgraphicssceneindex_p.h
+++ b/src/gui/graphicsview/qgraphicssceneindex_p.h
@@ -114,7 +114,7 @@ protected:
     virtual void itemChange(const QGraphicsItem *item, QGraphicsItem::GraphicsItemChange, const QVariant &value);
     virtual void prepareBoundingRectChange(const QGraphicsItem *item);
 
-    QGraphicsSceneIndex(QObjectPrivate &dd, QGraphicsScene *scene);
+    QGraphicsSceneIndex(QGraphicsSceneIndexPrivate &dd, QGraphicsScene *scene);
 
     friend class QGraphicsScene;
     friend class QGraphicsScenePrivate;
@@ -133,6 +133,7 @@ public:
     QGraphicsSceneIndexPrivate(QGraphicsScene *scene);
     ~QGraphicsSceneIndexPrivate();
 
+    void init();
     static bool itemCollidesWithPath(const QGraphicsItem *item, const QPainterPath &path, Qt::ItemSelectionMode mode);
 
     void recursive_items_helper(QGraphicsItem *item, QRectF exposeRect,
diff --git a/tests/auto/qgraphicssceneindex/tst_qgraphicssceneindex.cpp b/tests/auto/qgraphicssceneindex/tst_qgraphicssceneindex.cpp
index ac21e20..9d0675d 100644
--- a/tests/auto/qgraphicssceneindex/tst_qgraphicssceneindex.cpp
+++ b/tests/auto/qgraphicssceneindex/tst_qgraphicssceneindex.cpp
@@ -64,6 +64,7 @@ private slots:
     void overlappedItems();
     void movingItems_data();
     void movingItems();
+    void connectedToSceneRectChanged();
 
 private:
     void common_data();
@@ -214,6 +215,18 @@ void tst_QGraphicsSceneIndex::movingItems()
     QCOMPARE(scene.items(QRectF(0, 0, 1000, 1000)).count(), 11);
 }
 
+void tst_QGraphicsSceneIndex::connectedToSceneRectChanged()
+{
+
+    class MyScene : public QGraphicsScene
+    { public: using QGraphicsScene::receivers; };
+
+    MyScene scene; // Uses QGraphicsSceneBspTreeIndex by default.
+    QCOMPARE(scene.receivers(SIGNAL(sceneRectChanged(const QRectF&))), 1);
+
+    scene.setItemIndexMethod(QGraphicsScene::NoIndex); // QGraphicsSceneLinearIndex
+    QCOMPARE(scene.receivers(SIGNAL(sceneRectChanged(const QRectF&))), 1);
+}
 
 QTEST_MAIN(tst_QGraphicsSceneIndex)
 #include "tst_qgraphicssceneindex.moc"