Quote Originally Posted by caduel View Post
Only the gui thread my use QWidgets (and subclasses). Adding a QGraphicsItem to a scene (finally) calls the QGraphicsView(s) displaying that scene. So in all probability you may not do that in a separate thread.
Oh, the case you mention is not in my program. Because when I add item to scene, the scene is not added to view yet. so it won't try to "calls the QGraphicsView(s) displaying that scene". The design on 4.2.2 works well, I don't know whether there's any modification related with this problem on 4.4.0.