CODEWITHSUNDEEP
qt
kaa
kaa

Reputation: 1367

How to delete QGraphicsItem properly?

What I should to do to delete QGraphicsItem?

To remove item from the scene I use

 QGraphicsScene::removeItem(QGraphicsItem * item);

From the docs for this method:

i.e., QGraphicsScene will no longer delete item when destroyed

So I see only one way:

delete item;

But may be another? For example for QWidget is able to set attribute 

setAttribute( Qt::WA_DeleteOnClose );

That causes to deleting of the object. May be there is something similar for QGraphicsItem?

Upvotes: 10

Views: 15024

Answers (2)

alexei
alexei

Reputation: 21

It seems the issue lasting for long time today and there are open bugs also.

But it seems to have a workaround, which I could find it useful and after hours of debugging and reading and investigations I have found it here:

https://forum.qt.io/topic/71316/qgraphicsscenefinditembsptreevisitor-visit-crashes-due-to-an-obsolete-paintevent-after-qgraphicsscene-removeitem/17

Some other tips and tricks regarding Graphics Scene here: https://tech-artists.org/t/qt-properly-removing-qgraphicitems/3063/6

Upvotes: 0

Martin Prazak
Martin Prazak

Reputation: 1605

Unfortunately, QGraphicsItem is a base class of all graphics items usable inside QGraphicsScene, and, as most "item-like" objects in Qt, is not derived from QWidget or QObject. Moreover, they can only be parented to another QGraphicsItem (apart from being owned by QGraphicsScene.

After removing an item from a scene, unless it is parented to another QGraphicsItem, Qt expects the programmer to delete it manually by calling delete item; explicitly (or to use a smart pointer to manage the lifetime of the item after it was removed).

Upvotes: 11

Related Questions