QGraphicsScene::update() has no effect

[Lykurg]

First you don't have to call update if you alter an item, the scene makes that automatically. But you have to alter an item, you just alter a rect, which isn't connected to the item in any way! So do

QGraphicsRectItem *item = scene->addRect(*r, targetPen, targetBrush);
item->setRect(200, 200, 300, 300);

QGraphicsRectItem *item = scene->addRect(*r, targetPen, targetBrush);
item->setRect(200, 200, 300, 300);

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Further for performance reasons create QRect on the stack. And better don't use QRect's x and y when using an item on scene. Define that using the items position (QGraphicsRectItem::setPos()).