Incorrect mouse behavior in GraphicsScene

[framalex]

I'm trying to draw my own objects(inherited from QGraphicsItem) on my own scene (inherited from QGraphicsScene) on mouse click. When I handle mousePressEvent it puts new object in the wrong place (namely it doubles its coordinates while setting and speed while moving).

I handle MousePressEvent like this:

void PolygonScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
	if (mouseEvent->button() != Qt::LeftButton)
		return;
 
	PPoint *p = new PPoint(QColor(127, 0, 0), mouseEvent->scenePos().x(), mouseEvent->scenePos().y());
	addItem(p);
	QGraphicsScene::mousePressEvent(mouseEvent);
}

void PolygonScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
	if (mouseEvent->button() != Qt::LeftButton)
		return;

	PPoint *p = new PPoint(QColor(127, 0, 0), mouseEvent->scenePos().x(), mouseEvent->scenePos().y());
	addItem(p);
	QGraphicsScene::mousePressEvent(mouseEvent);
}

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And I create GraphicsScene and GraphicsView this way:

graphScene = new PolygonScene();
QPixmap pix = QPixmap::fromImage(image);
graphScene->clear();
graphScene->addPixmap(pix);
ui.graphicsView->setGeometry(QRect(5, 5, pix.width(), pix.height()));
ui.graphicsView->setViewportUpdateMode(QGraphicsView::SmartViewportUpdate);
ui.graphicsView->setScene(graphScene);
ui.graphicsView->show();

graphScene = new PolygonScene();
QPixmap pix = QPixmap::fromImage(image);
graphScene->clear();
graphScene->addPixmap(pix);
ui.graphicsView->setGeometry(QRect(5, 5, pix.width(), pix.height()));
ui.graphicsView->setViewportUpdateMode(QGraphicsView::SmartViewportUpdate);
ui.graphicsView->setScene(graphScene);
ui.graphicsView->show();

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Where should i look for the source of troube?
Thank you