[Paraview] Trouble with "information_only" GUI property in paraview filter

[Alex Rattner]

Hello,

I have been developing a feature tracking filter plug-in for paraview 
for a couple weeks. I am currently trying to improve the plug-in GUI, 
but ran into an issue.

I want the plug-in to return some basic information to the user in the 
GUI, so I added a property to the server xml file like:

<IntVectorProperty
    name="NumberOfFeatures"
    label="Number Of Features"
    command="GetNumFeatures"
    number_of_elements="1"
    default_values="0"
    information_only="1">
<Documentation>
       Number of features in the field.
</Documentation>
</IntVectorProperty>

with corresponding code in the class definition:
vtkGetMacro(NumFeatures, int);

However, the property does not appear on the plug-in gui. Similar 
"input" GUI properties work fine,  but I've been messing around for a 
couple hours and I cannot get this "output" GUI property to appear. Is 
this specific to the "filters" ProxyGroup - because I have found other 
plug-ins that use essentially the same xml code to output information? 
Do you have any suggestions on how to make such output properties 
display and work?

Thanks,
Alex