Updating the boundingRect of a QGraphicsItem

[robin2000]

hi,

i have a QGraphicsItemGroup with several items in it. The boundingRect is computed correctly according to the current boundingRects of the group members. Now i change the size of one member in the group, so that his boundingRect exceeds the group's boundingRect.
But when I call group.boundingRect(), it was not updated. Is there any way to manually update the boundingRect of an existing item group? Even implementing an inherited version of boundingRect() in a child class of QGraphicsItemGroup does not work, because boundingRect in QGraphicsItemGroup is not virtual thus the graphics engine would only call the ancestors version, when treating the object as a QGraphicsItem.
The only workaround i found is to remove an item from the group and adding it again, because then the boundingRect stored in the private variable d->itemsBoundingRect is updated. But that can't be the solution.

I'd be grateful for any ideas.

[wysota]

Sure it's virtual...

[robin2000]

No, boundingRect() is only virtual in QGraphicsItem not in QGraphicsItemGroup. Here is the code from the implementation:

/*!
    \reimp
 
    Returns the bounding rect of this group item, and all its children.
*/
QRectF QGraphicsItemGroup::boundingRect() const
{
    Q_D(const QGraphicsItemGroup);
    return d->itemsBoundingRect;
}

/*!
    \reimp

    Returns the bounding rect of this group item, and all its children.
*/
QRectF QGraphicsItemGroup::boundingRect() const
{
    Q_D(const QGraphicsItemGroup);
    return d->itemsBoundingRect;
}

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and the declaration in class QGraphicsItemGroup:

1062     QRectF boundingRect() const;

1062     QRectF boundingRect() const;

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[wysota]

#include <iostream>
class A {
public:
  virtual void function() { std::cout << "A" << std::endl; }
};
 
class B : public A {
public:
  void function() { std::cout << "B" << std::endl; }
};
 
class C : public B {
  void function() { std::cout << "C" << std::endl; }
};
 
int main(){
  A *obj = new A;
  obj->function();
  delete obj;
  obj = new B;
  obj->function();
  delete obj;
  obj = new C;
  obj->function();
  delete obj;
  return 0;
}

#include <iostream>
class A {
public:
  virtual void function() { std::cout << "A" << std::endl; }
};

class B : public A {
public:
  void function() { std::cout << "B" << std::endl; }
};

class C : public B {
  void function() { std::cout << "C" << std::endl; }
};

int main(){
  A *obj = new A;
  obj->function();
  delete obj;
  obj = new B;
  obj->function();
  delete obj;
  obj = new C;
  obj->function();
  delete obj;
  return 0;
}

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[robin2000]

Your so right. It didn't work in my case, because I tried to call QGraphicsItemGroup.boundingRect() instead of QGraphicsItem.boundingRect(). But that's easy to solve now.

Thank you very much for your fast help. Learned something about inheritance