Change GraphicsView settings to be more in line with Qml

Task-Number: BAUHAUS-567
Reviewed-by: kkoehne

src/plugins/qmldesigner/components/formeditor/formeditorgraphicsview.cpp

@@ -43,8 +43,9 @@ FormEditorGraphicsView::FormEditorGraphicsView(QWidget *parent) :
     setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
     setResizeAnchor(QGraphicsView::AnchorViewCenter);
 //    setCacheMode(QGraphicsView::CacheNone);
-     setCacheMode(QGraphicsView::CacheBackground);
+    setCacheMode(QGraphicsView::CacheBackground);
     setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);
+    setOptimizationFlags(QGraphicsView::DontSavePainterState);
 //    setViewportUpdateMode(QGraphicsView::NoViewportUpdate);
     setRenderHint(QPainter::Antialiasing, false);
 

src/plugins/qmldesigner/components/formeditor/formeditorscene.cpp

@@ -67,6 +67,7 @@ FormEditorScene::FormEditorScene(FormEditorWidget *view, FormEditorView *editorV
     m_formLayerItem->setZValue(0.0);
     m_formLayerItem->setFlag(QGraphicsItem::ItemClipsChildrenToShape, true);
     view->setScene(this);
+    setItemIndexMethod(QGraphicsScene::NoIndex);
 
 //    setItemIndexMethod(QGraphicsScene::NoIndex);
 }

src/plugins/qmldesigner/core/instances/nodeinstanceview.cpp

@@ -95,8 +95,10 @@ NodeInstanceView::NodeInstanceView(QObject *parent)
     m_blockStatePropertyChanges(false)
 {
     m_graphicsView->setAttribute(Qt::WA_DontShowOnScreen, true);
-    m_graphicsView->setViewportUpdateMode(QGraphicsView::NoViewportUpdate);
+    m_graphicsView->setOptimizationFlags(QGraphicsView::DontSavePainterState);
+    m_graphicsView->setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);
     m_graphicsView->setScene(new QGraphicsScene(m_graphicsView.data()));
+    m_graphicsView->scene()->setItemIndexMethod(QGraphicsScene::NoIndex);
 }