[Qgis-developer] Get a signal when the symbology changed

Denis Rouzaud denis.rouzaud at gmail.com
Wed Feb 26 01:46:39 PST 2014

Hi Guillaume,

On 26. 02. 14 10:15, Guillaume GIMENO wrote:
> Hi,
> I am working on a plugin and want to get a signal
> when the
> symbology
>  of a vector layer is changed by the user. In the doc, there is a 
> signal that seems to fit (
> http://qgis.org/api/classQgsVectorLayer.html#a403f235d3743aa59bb3aad69a72a5705
> )
> .
> I have
> tried two
>  method
> s
> called :
>     QObject.connect(self.iface.activeLayer(),
>     SIGNAL("rendererChanged()"), self.DoSomething)
> I have also tried :
>     self.iface.activeLayer().rendererChanged.connect(self.DoSomething)
> On os x mavericks nothing happens with the first method and for the 
> second I have a error :
>     AttributeError: 'QgsVectorLayer' object has no attribute
>     'rendererChanged'

I can't tell why, but you should use the second method as it is the new 
signal/slot connection style.
> But on Debian, I can get the signal but just for the layer which is 
> selected when the plugin is run ; On the other layers, if I change the 
> color, nothing happens.

This is because iface.activeLayer() is the currently selected layer in 
the legend. [0]
If you want to do so, you might want to connect all layers by browsing 
them using:
iface.mapCanvas().layers() if you want all the displayed layers actually 
displayed in the map
QgsMapLayerRegistry.instance(). mapLayers() if you want all the layers




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