How to scale an object which inherit QGrahicsItem within it's parent QGraphicsItem

[wysota]

You're using the wrong change value. I said ItemTransformChange not ItemTransformHasChanged.

[christina123y]

You're using the wrong change value. I said ItemTransformChange not ItemTransformHasChanged.

here is my code :

QVariant draw2dgraph::itemChange(GraphicsItemChange change, const QVariant &value)
{
    if(ItemTransformChange == change && parentItem() )
    {
         QTransform trans = transform();
         QRectF rect = trans.mapRect(boudingRect());
         if(parentItem()->boundingRect().size()!=rect.size())
        {
             rect = parentItem()->boundingRect();
        }
    }
    return QGraphicsItem::itemChange(change,value);
}

QVariant draw2dgraph::itemChange(GraphicsItemChange change, const QVariant &value)
{
    if(ItemTransformChange == change && parentItem() )
    {
         QTransform trans = transform();
         QRectF rect = trans.mapRect(boudingRect());
         if(parentItem()->boundingRect().size()!=rect.size())
        {
             rect = parentItem()->boundingRect();
        }
    }
    return QGraphicsItem::itemChange(change,value);
}

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but the draw2DGraph's object still outside it's parent boundingRect after it zoom in.
In draw2DGraph class I do zoom in function like this

void draw2DGraph::zoomIn()
{
    scale(1.2,1.2);
}

void draw2DGraph::zoomIn()
{
    scale(1.2,1.2);
}

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why ? why still happen like this? wish you help again! Thank you

[christina123y]

You're using the wrong change value. I said ItemTransformChange not ItemTransformHasChanged.

Can you help me? This problem has troubled me almost a week, I really need help? And I have look up reference on internet, but resolvation on this problem is so little. So I really need your help! Could you please provide me with some demo or sources on this problem!Thank you very much!

[wysota]

You have to map your size to your parent's coordinate space (or vice versa) based on the transform you get as the argument. This will allow you to compare your rectangle and the rectangle of your parent. Then you'll be able to correct the matrix based on the comparison (by scaling it back down).