QGraphicsScene::update() has no effect

[pmwalk]

I can't seem to get QGraphcsScene::update() to reflect any modifications I've made to items in the scene. Here is the shortest example where the problem is replicated:

QGraphicsScene *scene = new QGraphicsScene();
scene->setSceneRect(0, 0, 600, 600);
ui.map_view->setScene(scene);
QRectF *r = new QRectF(0, 0, 100, 100);
scene->addRect(*r, targetPen, targetBrush);
r->setRect(200, 200, 300, 300);
scene->update(scene->itemsBoundingRect());

QGraphicsScene *scene = new QGraphicsScene();
scene->setSceneRect(0, 0, 600, 600);
ui.map_view->setScene(scene);
QRectF *r = new QRectF(0, 0, 100, 100);
scene->addRect(*r, targetPen, targetBrush);
r->setRect(200, 200, 300, 300);
scene->update(scene->itemsBoundingRect());

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Because this is all done essentially instantaneously, I should see the 100x100 rectangle at 200, 200. Instead, it remains at 0, 0 (I checked to make sure I wasn't thinking (200, 200) was actually (0, 0)). Any thoughts?