'Re: [PyQt] Subclass of QGraphicsObject does not have the correct'

[prev in list] [next in list] [prev in thread] [next in thread] 

List:       pykde
Subject:    Re: [PyQt] Subclass of QGraphicsObject does not have the correct
From:       Selim Tuvi <Selim.Tuvi () pdi ! dreamworks ! com>
Date:       2011-05-20 16:01:34
Message-ID: 4DD6905E.7050206 () pdi ! dreamworks ! com
[Download RAW message or body]

[Attachment #2 (multipart/alternative)]

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.Tuvi@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
>   

[Attachment #5 (text/html)]

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
  <meta content="text/html;charset=UTF-8" http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
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.<br>
-Selim<br>
<br>
Phil Thompson wrote:
<blockquote cite="mid:e246ea0cb170d893c9223b12581a69df@localhost"
 type="cite">
  <pre wrap="">On Thu, 19 May 2011 14:42:47 -0700, Selim Tuvi
<a class="moz-txt-link-rfc2396E" \
href="mailto:Selim.Tuvi@pdi.dreamworks.com">&lt;Selim.Tuvi@pdi.dreamworks.com&gt;</a> \
wrote:  </pre>
  <blockquote type="cite">
    <pre wrap="">The code below outputs:

[&lt;__main__.Edge object at 0x2aaab0395830&gt;, &lt;PyQt4.QtGui.QGraphicsItem 
object at 0x2aaab03958c0&gt;]

which lists the Node instance as having the class QGraphicsItem when it 
should say &lt;__main__.Node object at ...&gt;.

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_())
    </pre>
  </blockquote>
  <pre wrap=""><!---->
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
  </pre>
</blockquote>
</body>
</html>

["Selim_Tuvi.vcf" (text/x-vcard)]

_______________________________________________
PyQt mailing list    PyQt@riverbankcomputing.com
http://www.riverbankcomputing.com/mailman/listinfo/pyqt

[prev in list] [next in list] [prev in thread] [next in thread] 