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On 01.07.2010 12:29, Phil Thompson wrote:
<blockquote cite="mid:ef8970bb83924866a35159bace39623f@localhost"
type="cite">
<pre wrap="">On Thu, 01 Jul 2010 11:58:01 +0200, "Christopher M. Nahler"
<a class="moz-txt-link-rfc2396E" href="mailto:christopher.nahler@papermodels.at"><christopher.nahler@papermodels.at></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">I want to add signalling functionality to scene items. In my case they
are usually QGraphicsRectItems..
I thought I could do this with deriving from QGraphicsObject but then I
loose all the funtionality for the rectangle, handling pens and brushes,
shapes etc.
Isn't it easier to just derive from QGraphicsRectItem and QObject? Or
should I derive from QGraphicsRectItem and QGraphicsObject instead?
</pre>
</blockquote>
<pre wrap="">
Neither. You can't multiply inherit from more than one PyQt class.
</pre>
<blockquote type="cite">
<pre wrap="">Or are there any other ways to do this?
</pre>
</blockquote>
<pre wrap="">
Create a QObject subclass that implements your signals as an attribute of
your QGraphicsRectItem.
Phil
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<font face="Courier New, Courier, monospace" size="-1"><br>
Thanks for the quick reply. I have tried to implement it that way but
stumbled over another problem I have in this case. I want to announce
that a MyRectangle was created (or has changed). When I want to add a
signalling object to my rectangle class I have to def it before. But
when I define the signal there I have to specify the data type which is
not yet defined.<br>
<br>
<br>
#!/usr/bin/env python<br>
# -*- coding: utf-8 -*-<br>
<br>
from PyQt4.QtCore import *<br>
from PyQt4.QtGui import *<br>
<br>
class Communicator(QObject):<br>
MyRectangleCreated = pyqtSignal(MyRectangle) <-- MyRectangle not
defined yet!<br>
<br>
def __init(self):<br>
super(Communicator, self).__init__(parent)<br>
<br>
<br>
class MyRectangle(QGraphicsRectItem):<br>
<br>
def __init__(self, rect=QRectF(0, 0, 0, 0), parent=None,
scene=None):<br>
super(MyRectangle, self).__init__(parent, scene)<br>
self.myCommunicator = Communicator()<br>
self.myCommunicator.MyRectangleCreated.emit(self)<br>
<br>
if __name__ == "__main__":<br>
r = MyRectangle()</font><br>
<br>
In genereal what I want to do is synchronize the QGraphicsItems from
the scene with a list of data objects. So when I create a graphics item
a data object in the data manager should be created and when I change a
graphics object the corresponding data block object should be updated.<br>
<br>
BTW right now I have the handling of the events (which creates and
changes graphics items) in a widget derived from a view.<br>
<br>
Any hints on the best approach for that?<br>
<br>
Thanks<br>
Chris<br>
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