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

[Phil Thompson]

On Mon, 5 Dec 2011 12:24:57 -0500, Luke Campagnola
<lcampagn at email.unc.edu>
wrote:
> Howdy Phil,
> I'm running into this issue where QGraphicsScene.items() does not
> return the correct python objects if the items are subclassed from
> QGraphicsObject. Your response to this issue several months ago was:
> 
> On Fri, May 20, 2011 at 11:46, Phil Thompson
> <phil at riverbankcomputing.com> wrote:
>> 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.
> 
> The workaround I am using for this bug is to maintain a dictionary
> that maps from the QtGui::QGraphicsItem memory address back to the
> original python object. Looks something like:
>     cache[ sip.unwrapinstance(sip.cast(item, QtGui.QGraphicsItem)) ] =
item
> 
> This works, but it's rather messy since every instance of
> QGraphicsObject and QGraphicsWidget needs to register itself with this
> cache. I presume PyQt already maintains a similar dictionary so that
> it can translate between Qt's internal memory addresses and PyQt's
> wrapper objects. Would it not be straightforward to implement my
> workaround from within PyQt?

Not straightforward, but certainly worth thinking about.

Do you have something small I can use as a test case?

Phil