[Qgis-developer] QgsRubberBand RuntimeError: underlying C/C++ object has been deleted

[Radim Blazek]

On Thu, Feb 13, 2014 at 7:13 AM, Denis Rouzaud <denis.rouzaud at gmail.com> wrote:
> Hi Radim,
>
> Can you show us the whole code?

https://github.com/blazek/spline/blob/master/spline/spline.py

Radim

> Cheers,
>
> Denis
>
>
> On 12. 02. 14 19:17, Radim Blazek wrote:
>>
>> On Wed, Feb 12, 2014 at 2:50 PM, Martin Dobias <wonder.sk at gmail.com>
>> wrote:
>>>
>>> Hi Radim
>>>
>>> On Wed, Feb 12, 2014 at 8:03 PM, Radim Blazek <radim.blazek at gmail.com>
>>> wrote:
>>>>
>>>> On Wed, Feb 12, 2014 at 1:45 PM, Radim Blazek <radim.blazek at gmail.com>
>>>> wrote:
>>>>>
>>>>> I am using rubber band in Python plugin:
>>>>>    self.rb = QgsRubberBand(self.canvas,  QGis.Polygon)
>>>>> and on mouse move
>>>>>    self.rb.addPoint( point, update )
>>>>>
>>>>> It works well on most systems only for Win7/32bit (QGIS 2.0.1, Python
>>>>> 2.7.4) it was reported that it fails with "RuntimeError: underlying
>>>>> C/C++ object has been deleted"
>>>
>>> When does it report the error - when closing QGIS?
>>
>> I don't know but I presume when map tool is used, it is called from
>> QgsMapTool::canvasMoveEvent().
>>
>> Radim
>>
>>>>> I see that ownership of rubber band is passed to map canvas
>>>>>
>>>>>     QgsRubberBand( QgsMapCanvas* mapCanvas /TransferThis/,
>>>>> QGis::GeometryType geometryType = QGis::Line );
>>>>>
>>>>> that is OK, but QgsMapCanvas should not delete QGraphicsItem until it
>>>>> is destructed.
>>>>>
>>>>> So how can the QgsRubberBand be deleted before QGIS is closed?
>>>>
>>>> BTW, because true owner of QGraphicsItem is QGraphicsScene, should not
>>>> we first mScene->removeItem() (which returns ownership) before item is
>>>> deleted in QgsMapCanvas destructor?
>>>
>>> That's the correct approach in Python (IIRC). You can remove the item
>>> in your map tool's deactivate() method.
>>>
>>> Regards
>>> Martin
>>
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>
>