Is it possible to get the old value from an observer?
Simple use case: If a user changes the name of a layer, I would like to get the old name of the layer and the new name. If
onLayerChanged provided arguments like (layers, new_layer, old_layer) this would be possible.
Can the method not provide this information because the old layer information has already been changed/deleted by the time
onLayerChanged is called?
Is the best solution to just save all layer names and then iterate for the one whose name no longer exists in
onLayerChanged and assume that is the changed one?