First pass of adding these features to the Slicer scalar bar actor class shows that there are some clashes in the way the two classes handle the labels/ticks, working through them now, but it's not a minor change.

A simple union of the two classes isn't going to work because of assumptions about the data type being formatted in the label and conflicting methods generating two sets of text actors.

The pop up Slice View Annotations Setting widget isn't using the ctkVTKScalarBarWidget, which in any case needs a lot of updating for new VTK6 options, as well as to add the text labels and the new PV settings.

I'd like to see the combination of the functionality, especially since having different scalar bar actors for 2d and 3d will be jarring, but they are two distinct subclasses of the VTK scalar bar actor and it's not going to be a quick fix to combine them.