You can reimplement the QGraphicsItem
's itemChange()
if you want to restrict movable area. Repositioning the item will cause itemChange
to get called. You should note that ItemSendsGeometryChanges
flag is needed to capture the change in position of QGraphicsItem
.
class MyItem : public QGraphicsRectItem
{
public:
MyItem(const QRectF & rect, QGraphicsItem * parent = 0);
protected:
virtual QVariant itemChange ( GraphicsItemChange change, const QVariant & value );
};
MyItem::MyItem(const QRectF & rect, QGraphicsItem * parent )
:QGraphicsRectItem(rect,parent)
{
setFlags(QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemSendsGeometryChanges);
}
QVariant MyItem::itemChange ( GraphicsItemChange change, const QVariant & value )
{
if (change == ItemPositionChange && scene()) {
// value is the new position.
QPointF newPos = value.toPointF();
QRectF rect = scene()->sceneRect();
if (!rect.contains(newPos)) {
// Keep the item inside the scene rect.
newPos.setX(qMin(rect.right(), qMax(newPos.x(), rect.left())));
newPos.setY(qMin(rect.bottom(), qMax(newPos.y(), rect.top())));
return newPos;
}
}
return QGraphicsItem::itemChange(change, value);
}
This will keep item moving limited to scene rect. You can define any arbitrary rect if you like.