QGraphicsItemChange not working for ItemPositionChange

[Narada]

I am trying out an example from
http://www.informit.com/store/c-plus...-9780132354165

Chap08/diagram.pro

The program compiles, but does not work as advertised. When you move the nodes, the links are supposed to move with the nodes. I used the debugger and found out that it never hits the if condition in

QVariant Node::itemChange(GraphicsItemChange change,
                          const QVariant &value)
{
    if (change == ItemPositionChange) {
        foreach (Link *link, myLinks)
            link->trackNodes();
    }
    return QGraphicsItem::itemChange(change, value);
}

QVariant Node::itemChange(GraphicsItemChange change,
                          const QVariant &value)
{
    if (change == ItemPositionChange) {
        foreach (Link *link, myLinks)
            link->trackNodes();
    }
    return QGraphicsItem::itemChange(change, value);
}

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If I take the if condition out, I sort of get to move the links, but after clicking on the graphics scene.

Any insight would be great into what the problem is.

[d_stranz]

Have you set the QGraphicsItem::ItemSendsGeometryChanges and maybe QGraphicsItem::ItemSendsScenePositionChanges flags on your Node instances? These flags are both off by default, which means you will not get itemChange events for ItemPositionChange and other transform changes.

[Narada]

That was it. Didn't know there was such a flag. Thank you very much.

[anda_skoa]

That was it. Didn't know there was such a flag. Thank you very much.

The example in the book had code for the position change handling but not for setting the flags?

Cheers,
_

[Narada]

That's correct. However, at the time the book was written the flag was set automatically. Later Qt changed the default values ( around 4.7).