My QGIS 2.8.2 standalone app provides several decorating layers (e.g. cartographic grid, background layers, reference points) which should be not changed by the user (neither editing nor hiding), as well as layers, the user can modify and query.
The app has a legend widget which shows all layers, since all layers are registered with map registry. The widget is populated with the layer tree as described in How to add a legend to a canvas in a standalone PyQGIS application?.
Instead of exposing all layers in the tree view, I want to restrict the tree view to the layer group, whose children represent the user mutable layers. Thus the user can change visibility and ordering of only these layers, and must keep the decoration as it is.
What I tried so far is to initiate QgsLayerTreeMapCanvasBridge with this group node (instead of layerTreeRoot), pass the group node to QgsLayerTreeModel(), or changed the root group of the model with QgsLayerTreeModel.setRootGroup(). In each case Python crashes, with an error message like this:
QObject::connect: Cannot connect (null)::willAddChildren( QgsLayerTreeNode*, int, int ) to QgsLayerTreeModel::nodeWillAddChildren( QgsLayerTreeNode*, int, int )
Is it possible to expose only some group oder layer nodes in the treeview, and how can I implement this?