Fixes QGraphicsWidget: paint() being called before polish().

The problem is that we request an update() before we schedules a polish
event in QGraphicsScene::addItems, which means paint() is being called before
polishEvent(). We could try to swap the order in addItems, but that
doesn't give us any guarantee that polish is delivered before update
(since we have no control over what's happening from outside graphics
view). A better solution is to always make sure we don't have unpolished
items before we draw.

Auto-test included.

Task-number: QTBUG-4979
Reviewed-by: Andreas

2 files changed, 35 insertions, 0 deletions

diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index 13f31b8..5b0643d 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -4551,6 +4551,10 @@ void QGraphicsScenePrivate::drawItemHelper(QGraphicsItem *item, QPainter *painte
 void QGraphicsScenePrivate::drawItems(QPainter *painter, const QTransform *const viewTransform,
                                       QRegion *exposedRegion, QWidget *widget)
 {
+    // Make sure we don't have unpolished items before we draw.
+    if (!unpolishedItems.isEmpty())
+        _q_polishItems();
+
     QRectF exposedSceneRect;
     if (exposedRegion && indexMethod != QGraphicsScene::NoIndex) {
         exposedSceneRect = exposedRegion->boundingRect().adjusted(-1, -1, 1, 1);
@@ -5077,6 +5081,10 @@ void QGraphicsScene::drawItems(QPainter *painter,
                                const QStyleOptionGraphicsItem options[], QWidget *widget)
 {
     Q_D(QGraphicsScene);
+    // Make sure we don't have unpolished items before we draw.
+    if (!d->unpolishedItems.isEmpty())
+        d->_q_polishItems();
+
     QTransform viewTransform = painter->worldTransform();
     Q_UNUSED(options);
 
diff --git a/tests/auto/qgraphicswidget/tst_qgraphicswidget.cpp b/tests/auto/qgraphicswidget/tst_qgraphicswidget.cpp
index 6b5ad09..829e55c 100644
--- a/tests/auto/qgraphicswidget/tst_qgraphicswidget.cpp
+++ b/tests/auto/qgraphicswidget/tst_qgraphicswidget.cpp
@@ -160,6 +160,7 @@ private slots:
     void widgetSendsGeometryChanges();
     void respectHFW();
     void addChildInpolishEvent();
+    void polishEvent();
 
     // Task fixes
     void task236127_bspTreeIndexFails();
@@ -2768,6 +2769,32 @@ void tst_QGraphicsWidget::addChildInpolishEvent()
     QCOMPARE(PolishWidget::numberOfPolish, 2);
 }
 
+void tst_QGraphicsWidget::polishEvent()
+{
+    class MyGraphicsWidget : public QGraphicsWidget
+    { public:
+        void paint(QPainter *, const QStyleOptionGraphicsItem *, QWidget *)
+        { events << QEvent::Paint; }
+        void polishEvent()
+        { events << QEvent::Polish; }
+        QList<QEvent::Type> events;
+    };
+
+    QGraphicsScene scene;
+
+    MyGraphicsWidget *widget = new MyGraphicsWidget;
+    scene.addItem(widget);
+
+    QGraphicsView view(&scene);
+    view.show();
+    QTest::qWaitForWindowShown(&view);
+
+    // Make sure the item is painted.
+    QTRY_VERIFY(widget->events.contains(QEvent::Paint));
+
+    // Make sure the item got polish before paint.
+    QCOMPARE(widget->events.at(0), QEvent::Polish);
+}
 
 QTEST_MAIN(tst_QGraphicsWidget)
 #include "tst_qgraphicswidget.moc"