Move QGraphicsItem with mouse hover

Question

I'm trying to move a QGraphicsItem with the mouse hover over the parent item.

BaseItem::BaseItem(const QRectF &bounds) : theBounds(bounds), theMousePressed(false) { theLineItem = new LineItem(theBounds, this); setAcceptHoverEvents(true); }

and

void BaseItem::hoverEnterEvent(QGraphicsSceneHoverEvent *event) { QPointF position = mapToScene( event->pos()); theLineItem->setPos( position); }

But the item is not moving. Is there any other way to move the item on the scene with mouse move, without using the ItemIsMovable flag, because I want the item to be moved around the parent item, once it's invoked?

TheDarkKnight · Accepted Answer · 2013-11-19 11:17:47Z

When you create the LineItem, in its constructor you pass the BaseItem as the parent.

A call to setPos on a GraphicsItem, sets the position of the item relative to its parent which, in this case, is the BaseItem.

Mapping the event->pos() to scene coordinates is wrong here. event->pos() returns the position in local coordinates of the receiving object, which in this case is the BaseItem.

Therefore, you should be setting the position of theLineItem directly with event->pos().

theLineItem->setPos(event->pos());

Note that if you did happen to want the event position in scene coordinates, there's a function already available: -

event->scenePos();

So you would not have needed to call mapToScene.

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