QGraphicsItem discard updates when it shouldn't.

Once a _q_processDirtyItems call is queued, it means we at least have
one item that is marked as dirty and we must reset it when the
_q_processDirtyItems slot is called. The problem however, was that
we didn't reset the item's dirty state if a full scene update occurred
in between, i.e. item->update(); scene.update();

We don't have to calculate the item's dirty rect if a full scene update
occurs in between, but we still have to reset its state.

Auto-test included.

3 files changed, 36 insertions, 6 deletions

diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index caf9309..ad392b0 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -679,19 +679,19 @@ void QGraphicsScenePrivate::_q_processDirtyItems()
 {
     processDirtyItemsEmitted = false;
 
-    if (updateAll)
-        return;
-
     const bool wasPendingSceneUpdate = calledEmitUpdated;
     const QRectF oldGrowingItemsBoundingRect = growingItemsBoundingRect;
     processDirtyItemsRecursive(0);
     if (!hasSceneRect && oldGrowingItemsBoundingRect != growingItemsBoundingRect)
         emit q_func()->sceneRectChanged(growingItemsBoundingRect);
 
+    if (wasPendingSceneUpdate)
+        return;
+
     for (int i = 0; i < views.size(); ++i)
         views.at(i)->d_func()->processPendingUpdates();
 
-    if (!wasPendingSceneUpdate && calledEmitUpdated) {
+    if (calledEmitUpdated) {
         // We did a compatibility QGraphicsScene::update in processDirtyItemsRecursive
         // and we cannot wait for the control to reach the eventloop before the
         // changed signal is emitted, so we emit it now.
@@ -5322,7 +5322,6 @@ void QGraphicsScenePrivate::markDirty(QGraphicsItem *item, const QRectF &rect, b
 
 void QGraphicsScenePrivate::processDirtyItemsRecursive(QGraphicsItem *item, bool dirtyAncestorContainsChildren)
 {
-    Q_ASSERT(!item || item->d_ptr->dirty || item->d_ptr->dirtyChildren);
     Q_Q(QGraphicsScene);
 
     // Calculate the full scene transform for this item.
@@ -5438,13 +5437,15 @@ void QGraphicsScenePrivate::processDirtyItemsRecursive(QGraphicsItem *item, bool
                 continue;
             }
 
-            if (dirtyAncestorContainsChildren) {
+            if (dirtyAncestorContainsChildren || updateAll) {
                 // No need to process this child's dirty rect, hence reset the dirty state.
                 // However, we have to continue the recursion because it might have a dirty
                 // view bounding rect that needs repaint. We also have to reset the dirty
                 // state of its descendants.
                 child->d_ptr->dirty = 0;
                 child->d_ptr->fullUpdatePending = 0;
+                if (updateAll)
+                    child->d_ptr->paintedViewBoundingRectsNeedRepaint = 0;
             }
 
             processDirtyItemsRecursive(child, dirtyAncestorContainsChildren);
diff --git a/src/gui/graphicsview/qgraphicsview.cpp b/src/gui/graphicsview/qgraphicsview.cpp
index 87b5e3f..a9fc563 100644
--- a/src/gui/graphicsview/qgraphicsview.cpp
+++ b/src/gui/graphicsview/qgraphicsview.cpp
@@ -2496,6 +2496,7 @@ void QGraphicsView::updateScene(const QList<QRectF> &rects)
     for (int i = 0; i < dirtyRects.size(); ++i)
         dirtyViewportRects += dirtyRects.at(i);
     d->dirtyRegion = QRegion();
+    d->dirtyBoundingRect = QRect();
 
     bool fullUpdate = !d->accelerateScrolling || d->viewportUpdateMode == QGraphicsView::FullViewportUpdate;
     bool boundingRectUpdate = (d->viewportUpdateMode == QGraphicsView::BoundingRectViewportUpdate)
diff --git a/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp b/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp
index 427ecf3..5b297f6 100644
--- a/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp
+++ b/tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp
@@ -219,6 +219,7 @@ private slots:
     void updateCachedItemAfterMove();
     void deviceTransform_data();
     void deviceTransform();
+    void update();
 
     // task specific tests below me
     void task141694_textItemEnsureVisible();
@@ -6427,5 +6428,32 @@ void tst_QGraphicsItem::deviceTransform()
     QCOMPARE(rect3->deviceTransform(deviceX).map(QPointF(50, 50)), mapResult3);
 }
 
+void tst_QGraphicsItem::update()
+{
+    QGraphicsScene scene;
+    QGraphicsView view(&scene);
+    view.show();
+#ifdef Q_WS_X11
+    qt_x11_wait_for_window_manager(&view);
+#endif
+    QTest::qWait(100);
+
+    EventTester *item = new EventTester;
+    scene.addItem(item);
+    QTest::qWait(100); // Make sure all pending updates are processed.
+    item->repaints = 0;
+
+    item->update(); // Item marked as dirty
+    scene.update(); // Entire scene marked as dirty
+    qApp->processEvents();
+    QCOMPARE(item->repaints, 1);
+
+    // Make sure the dirty state from the previous update is reset so that
+    // the item don't think it is already dirty and discards this update.
+    item->update();
+    qApp->processEvents();
+    QCOMPARE(item->repaints, 2);
+}
+
 QTEST_MAIN(tst_QGraphicsItem)
 #include "tst_qgraphicsitem.moc"