Re: [PyQt] Subclass of QGraphicsObject does not have the correct class name listed in QGraphicsScene.items()

[Selim Tuvi]

Hi Phil, thanks for the explanation. The issue came up where I need to 
do special processing based on the type of the item. I'll rely on my own 
"itemtype" property instead.
-Selim

Phil Thompson wrote:
On Thu, 19 May 2011 14:42:47 -0700, Selim Tuvi
<selim.t...@pdi.dreamworks.com> wrote:
  
The code below outputs:
[<__main__.Edge object at 0x2aaab0395830>, <PyQt4.QtGui.QGraphicsItem 
object at 0x2aaab03958c0>]

which lists the Node instance as having the class QGraphicsItem when it 
should say <__main__.Node object at ...>.

Tested on (Qt 4.7.2, PyQt 4.8.3) and (Qt 4.6.1, PyQt 4.7.2)

Thanks
-Selim

from PyQt4 import QtGui, QtCore

class Node(QtGui.QGraphicsObject):
    def __init__(self):
        QtGui.QGraphicsObject.__init__(self)
       
    def paint(self, painter, option, widget):
        pass
       
    def boundingRect(self):
        return QtCore.QRectF()

class Edge(QtGui.QGraphicsItem):
    def __init__(self):
        QtGui.QGraphicsItem.__init__(self)

    def paint(self, painter, option, widget):
        pass

    def boundingRect(self):
        return QtCore.QRectF()

if __name__ == '__main__':
    import sys
    app = QtGui.QApplication(sys.argv)
    print QtCore.QT_VERSION_STR, QtCore.PYQT_VERSION_STR
    view = QtGui.QGraphicsView()
    scene = QtGui.QGraphicsScene()
    view.setScene(scene)
    scene.addItem(Node())
    scene.addItem(Edge())
    print scene.items()
    view.show()
    sys.exit(app.exec_())
    

It's because QGraphicsObject inherits both QObject and QGraphicsItem.
items() returns a list of QGraphicsItems which, for a QGraphicsObject, has
a different C++ address than the original QGraphicsObject. PyQt doesn't
recognise that the QGraphicsItem is a cast of the QGraphicsObject. I don't
think there is anything I can (sensibly) do about this.

Phil
  
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