Fix regression in clip path calculation for QGraphicsWidget.

This fixes a regression when computing the clip path for a
QGraphicsWidget that clip its children to its shape. The clip path cache
use the bounding rect which has a null width and height the very first
time on a QGraphicsWidget. This might happen as well for any item that
have a null width and height (e.g. QGraphicsRectItem before you set the
rect). We should do better in mainline by refactoring this clip path
cache and calling it in prepareGeometryChange which should be called
when you update the shape and the boundingRect of the item. Do we
really need also in 4.6/mainline the clip path as it is now? This should
be investigate also. The auto-test cover the problem so we can use it
after for refactoring the cached clip path.

Task-number: 257232
Reviewed-by: andreas
Reviewed-by: bnilsen

2 files changed, 84 insertions, 0 deletions

diff --git a/src/gui/graphicsview/qgraphicswidget.cpp b/src/gui/graphicsview/qgraphicswidget.cpp
index d52337dfb..525cf29a3 100644
--- a/src/gui/graphicsview/qgraphicswidget.cpp
+++ b/src/gui/graphicsview/qgraphicswidget.cpp
@@ -411,6 +411,8 @@ void QGraphicsWidget::setGeometry(const QRectF &rect)
     QSizeF oldSize = size();
     QGraphicsLayoutItem::setGeometry(newGeom);
 
+    wd->invalidateCachedClipPathRecursively();
+
     // Send resize event
     bool resized = newGeom.size() != oldSize;
     if (resized) {
diff --git a/tests/auto/qgraphicswidget/tst_qgraphicswidget.cpp b/tests/auto/qgraphicswidget/tst_qgraphicswidget.cpp
index 8fa4dc357..cb5f057b8 100644
--- a/tests/auto/qgraphicswidget/tst_qgraphicswidget.cpp
+++ b/tests/auto/qgraphicswidget/tst_qgraphicswidget.cpp
@@ -149,6 +149,7 @@ private slots:
     void closePopupOnOutsideClick();
     void defaultSize();
     void shortcutsDeletion();
+    void ensureClipping();
 
     // Task fixes
     void task236127_bspTreeIndexFails();
@@ -1928,6 +1929,87 @@ void tst_QGraphicsWidget::task250119_shortcutContext()
     scene.removeItem(&w_signal);
 }
 
+class ClippingAndTransformsScene : public QGraphicsScene
+{
+public:
+    QList<QGraphicsItem *> drawnItems;
+protected:
+    void drawItems(QPainter *painter, int numItems, QGraphicsItem *items[],
+                   const QStyleOptionGraphicsItem options[], QWidget *widget = 0)
+    {
+        drawnItems.clear();
+        for (int i = 0; i < numItems; ++i)
+            drawnItems << items[i];
+        QGraphicsScene::drawItems(painter, numItems, items, options, widget);
+    }
+};
+
+class RectWidget : public QGraphicsWidget
+{
+public:
+
+    RectWidget(Qt::GlobalColor color, QGraphicsItem *parent=0) : QGraphicsWidget(parent), mColor(color) {}
+
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
+    {
+        painter->setBrush(QBrush(mColor));
+        painter->drawRect(boundingRect());
+    }
+
+    Qt::GlobalColor mColor;
+};
+
+class RectItem : public QGraphicsItem
+{
+public:
+
+    RectItem(Qt::GlobalColor color, QGraphicsItem *parent=0) : QGraphicsItem(parent), mColor(color) {}
+
+    QRectF boundingRect() const
+    {return QRectF(10,10,50,50);}
+
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
+    {
+        painter->setBrush(QBrush(mColor));
+        painter->drawRect(boundingRect());
+    }
+
+    Qt::GlobalColor mColor;
+};
+
+void tst_QGraphicsWidget::ensureClipping()
+{
+    ClippingAndTransformsScene scene;
+    scene.setSceneRect(-50, -50, 200, 200);
+
+    //A root that clip children
+    RectWidget *clipWidget = new RectWidget(Qt::black);
+    scene.addItem(clipWidget);
+
+    clipWidget->setFlag(QGraphicsItem::ItemClipsChildrenToShape);
+
+    //a child
+    RectWidget *childWidget = new RectWidget(Qt::red, clipWidget);
+    clipWidget->setGeometry(QRectF(10, 10, 100, 100));
+    childWidget->setGeometry(QRectF(25, 25, 50, 50));
+
+    //We put a QGraphicsItem to be sure this one is also paint
+    RectItem *childitem = new RectItem(Qt::blue, clipWidget);
+
+    QGraphicsView view(&scene);
+    view.show();
+#ifdef Q_WS_X11
+    qt_x11_wait_for_window_manager(&view);
+#endif
+    QTest::qWait(250);
+
+    QList<QGraphicsItem *> expected;
+    expected << clipWidget << childWidget << childitem;
+    QVERIFY(scene.drawnItems.contains(clipWidget));
+    QVERIFY(scene.drawnItems.contains(childWidget));
+    QVERIFY(scene.drawnItems.contains(childitem));
+}
+
 QTEST_MAIN(tst_QGraphicsWidget)
 #include "tst_qgraphicswidget.moc"