[Qgis-developer] Need help with Plugin button behavior connected to SIGNAL("selectionChanged()")

[Denis Rouzaud]

Btw, I have created a pull request for this. Hopefully, it will be in 
core for 2.1 !


On 08/22/2013 02:11 PM, Alexandre Neto wrote:
> Hello all,
>
> I'm updating the Multipart split plugin 
> <http://plugins.qgis.org/plugins/splitmultipart/> to make it work with 
> the 2.0 API.
>
> Has I have successfully updated the plugin to make it work in 2.0, I 
> would like to improve it's button behavior to work like the rest of 
> the advanced editing toolbar. I am able to enable and disable it if 
> the current layer is editable.
>
> Now I'm trying to get the same behavior if there are selected 
> features. I have made it work, but QGIS starts to get really slow... I 
> found out that's because lots of connections are being created to 
> SIGNAL("selectionChanged()").
>
> Can someone please, point me in the right direction, or tell me where 
> can I find some code example doing this?
>
> Thank you very much,
>
> Alexandre Neto
>
> Part of the code bellow:
>
> def initGui(self):
>         # Create action that will start plugin configuration
>         self.action = QAction(
>             QIcon(":/plugins/splitmultipart/icon.svg"),
>             QCoreApplication.translate('Multipart split', u"Split 
> Selected Multipart features"), self.iface.mainWindow())
>         self.action.setEnabled(False)
>         # connect to signals for button behavior
>         QObject.connect(self.action, SIGNAL("triggered()"), self.run)
>         QObject.connect(self.iface, 
> SIGNAL("currentLayerChanged(QgsMapLayer*)"), self.toggle)
>         #QObject.connect(self.iface, 
> SIGNAL("selectionChanged(QgsMapLayer *)"), self.toggle)
>
>         # Add toolbar button and menu item
> self.iface.advancedDigitizeToolBar().addAction(self.action)
>         self.iface.editMenu().addAction(self.action)
>     def toggle(self):
>         mc = self.canvas
>         layer = mc.currentLayer()
>         # Decide whether the plugin button is enable or disable
>         if layer <> None:
>             # set enable
>             if layer.isEditable():
> QObject.connect(layer,SIGNAL("editingStopped()"),self.toggle)
>                 QObject.connect(layer, SIGNAL("selectionChanged()"), 
> self.toggle)
> QObject.disconnect(layer,SIGNAL("editingStarted()"),self.toggle)
> self.iface.messageBar().pushMessage("Debug"," Connect 
> SIGNAL(selectionChanged()",0)
>                 if layer.selectedFeatureCount() > 0:
>                     self.action.setEnabled(True)
>                 else:
>                     self.action.setEnabled(False)
>             # set disable
>             else:
>                 self.action.setEnabled(False)
> QObject.connect(layer,SIGNAL("editingStarted()"),self.toggle)
> QObject.disconnect(layer,SIGNAL("editingStopped()"),self.toggle)
>                 QObject.disconnect(layer, 
> SIGNAL("selectionChanged()"), self.toggle)
> self.iface.messageBar().pushMessage("Debug"," Disconnect 
> SIGNAL(selectionChanged()",0)
>
>
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