[Paraview] avoiding proxy ID collisions

[Geoff Draper]

I've written a program which exports ParaView's undo stack as a series of 
vtkUndoSet objects, serialized to XML.  (This is done by calling 
vtkUndoSet::SaveState(), and then calling PrintXML() on the returned 
vtkPVXMLElement object.)  The idea is to be able to import the saved undo 
stack into a blank scene, and step through the stack, "redo"-ing each 
vtkUndoSet.

Although the export works just fine, importing the undo stack is 
more problematic.  The problem is that each vtkSMProxy object has an ID 
number which is guaranteed to be unique during a single ParaView runtime 
session, but which is NOT necessarily unique from one session to another. 
So when I re-run ParaView and import my saved undo stack, occasionally 
the ID numbers for the proxies stored in the XML file will conflict with 
ID numbers already in use by existing vktSMProxy objects.  So when I 
attempt to redo the vtkUndoSets, ParaView pops up an error dialog 
and exits.  (I'm using vtkSMUndoRedoStateLoader::LoadUndoRedoSet() to 
load in the vtkUndoSet objects.)

My question is: Is there a straightforward way to auto-increment the ID 
numbers when loading saved proxy objects, in the case of ID-number 
conflicts?

Thanks,
Geoff

P.S. The specific error message I'm seeing is:
"""
ERROR: In ..\..\..\Servers\Common\vtkProcessModule.cxx, line 1091
vtkProcessModule (082F8B38): Attempting to assign existing ID 74.
while processsing
Message 0 = Assign
   Argument 0 = id_value {74}
   Argument 1 = vtk_object_pointer {vtkSMSourceProxy (0A634EB0)}
"""