The problem of copying a class by block copying its memory with malloc is that if the class contains pointers to objects or arrays, then only a shallow copy will occur.
In your case of getting pointers to a QGraphicsItem, you'll need to identify the type of item you're copying (its actual child class, not base class) and use the copy constructor. QGraphicsItem includes a function called type(), which returns an int that indicates which item it is. You can also add to this in your own derived classes by implementing the type() function. For example, from the Qt docs: -
class CustomItem : public QGraphicsItem
{
...
enum { Type = UserType + 1 };
int type() const
{
// Enable the use of qgraphicsitem_cast with this item.
return Type;
}
...
};
Alternatively, if all the classes are your own type, you could use your own system. Once you know the type, you can then copy the item with its copy constructor: -
// Example, assuming type denotes a QGraphicsItemRect
QGraphicsItemRect rect = (*originalRect);
Note that if you have inherited from QGraphicsItem and added members that are pointers, you'll need to add your own copy constructor to ensure a deep copy occurs, instead of a shallow copy.