Fixed rendering bugs when scrolling graphics items with drop shadows.

We can't clip source pixmaps to the device rect, as there's no way of
knowing which parts of the source pixmap are needed for the part of the
graphics effect that's unclipped.

Reviewed-by: Bjørn Erik Nilsen

1 files changed, 5 insertions, 18 deletions

diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index afea082..4ee2301 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -4714,31 +4714,18 @@ void QGraphicsScenePrivate::drawSubtreeRecursive(QGraphicsItem *item, QPainter *
         if (sourced->currentCachedSystem() != Qt::LogicalCoordinates
             && sourced->lastEffectTransform != painter->worldTransform())
         {
-            bool unclipped = false;
             if (sourced->lastEffectTransform.type() <= QTransform::TxTranslate
                 && painter->worldTransform().type() <= QTransform::TxTranslate)
             {
-                QRectF itemRect = item->boundingRect();
-                if (!item->d_ptr->children.isEmpty())
-                    itemRect |= item->childrenBoundingRect();
+                QRectF sourceRect = sourced->boundingRect(Qt::DeviceCoordinates);
+                QRect effectRect = sourced->paddedEffectRect(Qt::DeviceCoordinates, sourced->currentCachedMode(), sourceRect);
 
-                QRectF oldSourceRect = sourced->lastEffectTransform.mapRect(itemRect);
-                QRectF newSourceRect = painter->worldTransform().mapRect(itemRect);
-
-                QRect oldEffectRect = sourced->paddedEffectRect(sourced->currentCachedSystem(), sourced->currentCachedMode(), oldSourceRect);
-                QRect newEffectRect = sourced->paddedEffectRect(sourced->currentCachedSystem(), sourced->currentCachedMode(), newSourceRect);
-
-                QRect deviceRect(0, 0, painter->device()->width(), painter->device()->height());
-                if (deviceRect.contains(oldEffectRect) && deviceRect.contains(newEffectRect)) {
-                    sourced->setCachedOffset(newEffectRect.topLeft());
-                    unclipped = true;
-                }
+                sourced->setCachedOffset(effectRect.topLeft());
+            } else {
+                sourced->invalidateCache(QGraphicsEffectSourcePrivate::TransformChanged);
             }
 
             sourced->lastEffectTransform = painter->worldTransform();
-
-            if (!unclipped)
-                sourced->invalidateCache(QGraphicsEffectSourcePrivate::TransformChanged);
         }
 
         item->d_ptr->graphicsEffect->draw(painter);