[Qgis-developer] Memory provider saver and signals

[Chris Crook]

Hi All

I'm trying to find some good signals for identifying changes to data in a memory layer.

I've got a functional memory provider plugin, at the moment saving each memory layer to a GML file.  However I'm not sure I've got the best approach to identifying when data changes are made to memory layers so that I can identify when the layers need to be updated.

The best I've got so far is 
            QObject.connect(layer, SIGNAL("committedAttributesDeleted(const QString &, const QgsAttributeIds )"),self.setProjectDirty2)
            QObject.connect(layer, SIGNAL("committedAttributesAdded(const QString &, const QList<QgsField> &)"),self.setProjectDirty2)
            QObject.connect(layer, SIGNAL("committedFeaturesDeleted(const QString &, const QgsFeatureIds & )"),self.setProjectDirty2)
            QObject.connect(layer, SIGNAL("committedFeaturesAdded(const QString &, const QgsFeatureIds &)"),self.setProjectDirty2)
            QObject.connect(layer, SIGNAL("committedAttributeValuesChanges(const QString &, const QgsChangedAttributesMap &)"),self.setProjectDirty2)

This works (at least for user changes - it won't identify changes made by other plugins, for example).  But it does seem a bit cumbersome.  

I'd hoped find something directly from the provider, since this would also identify programmatic data changes.  I thought I was onto something when I saw  

            QgsDataProvider.dataChanged()

>From its name this seemed perfect, but the documentation states it is for a different purpose - asynchronous tasks registering completion of data changes :-(  And looking through the memory provider code, I can't see any signals being emitted.

I'd also thought that using QgsVectorLayer.layerModified(bool) might have been a bit more succinct.  But that gets triggered more often than I want.  

Is there any obvious signal I'm missing?

Thanks
Chris
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