[Qgis-developer] wrapping changeAttributeValue between begin and end EditCommand

[Martin Dobias]

Hi Francesco

Currently it is not safe to do calls that modify vector layer data in slots
connected to signals notifying about data change (such as featureAdded).
The issue is that at the point when those signals are emitted, their
underlying undo commands were not yet pushed onto the stack, so doing
further editing calls causes corruption of undo stack (undo command for
follow up operation is placed before the first operation).

As a workaround you could defer the change attribute operations - e.g. with
a QTimer. Not an elegant solution though...

Regards
Martin


On Sun, Mar 15, 2015 at 9:04 PM, francescoboccacci at libero.it <
francescoboccacci at libero.it> wrote:

>
> Hi all,
> i have a problem with beginEditCommand and endEditCommand wrapping.
> In my plugin i capture the layer.featureAdded signal :
> self.layer.featureAdded.connect(self.myfunction)
>  The scope of my function is to change attribute of the feature added
> according with some rules.
> I wrap self.layer.changeAttributevalue between
> self.layer.beginEditCommand('My custom value') and
> self.layer.endEditCommand() but when i added a feature i can't see in
> Undo/redo window the label My custom value but my value is changed.
> This cause a Qgis 2.8.2 crash when i try to rollback my changes.
>
> P.S If i comment my change values function and i write the code in a
> python console i can see  my beginEditCommand label and no crash happend.
>
> Anyone can help me?
>
> Thanks
>
> Francesco
>
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