Fixed DeviceCoordinateCache items when using QGraphicsScene::render().

Since viewRect is null, we shouldn't try to use the partialCacheExposure
path which intersects the viewRect with the device rect of the item.

Task-number: QTBUG-15977
Reviewed-by: Bjørn Erik Nilsen

1 files changed, 2 insertions, 2 deletions

diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index a0015dc..726e6d7 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -4583,13 +4583,13 @@ void QGraphicsScenePrivate::drawItemHelper(QGraphicsItem *item, QPainter *painte
             itemCache->exposed.clear();
             deviceData->cacheIndent = QPoint();
             pix = QPixmap();
-        } else {
+        } else if (!viewRect.isNull()) {
             allowPartialCacheExposure = deviceData->cacheIndent != QPoint();
         }
 
         // Allow partial cache exposure if the device rect isn't fully contained and
         // deviceRect is 20% taller or wider than the viewRect.
-        if (!allowPartialCacheExposure && !viewRect.contains(deviceRect)) {
+        if (!allowPartialCacheExposure && !viewRect.isNull() && !viewRect.contains(deviceRect)) {
             allowPartialCacheExposure = (viewRect.width() * 1.2 < deviceRect.width())
                                          || (viewRect.height() * 1.2 < deviceRect.height());
         }