[Paraview] Invoke remote procedure from proxy with argument and return value

[Mario Schreiber]

Why is it so complicated to call a procedure and receive a return value on
the client?

I am attaching my attempt (CMakeLists.txt, vtkSquareFun.cxx, vtkSquareFun.h
and TestPlugin.xml, each less than 20 lines of code), which basically
calculates the square of an argument in vtkSquareFun::eval(double x).

When I load this plugin in Paraview and open the Python Shell, I can
evaluate vtkSquareFun::eval() using a detour by first setting the argument
and then getting the result, which is linked to the argument property in
TestPlugin.xml:

fun=servermanager.CreateProxy("test","SquareFun")
fun.GetProperty("Arg").SetElement(0,999)
fun.UpdateVTKObjects()
fun.UpdatePropertyInformation()
fun.GetProperty("Result").GetElement(0)
... showing the correct result 998001.

Why can't I simply run the following?
fun=servermanager.CreateProxy("test","SquareFun")
result=fun.InvokeCommand("eval",[999.0])

Does Paraview really not provide any means of calling a function with
arguments and return value within a single client-server communication? All
these individual message transfers are a bottleneck in our application.
Does the Paraview architecture exclude more universal remote procedure
calls, or do you think that one could just augment the available procedures
with another procedure that can deliver a set of custom return values?

Thanks
Mario


2016-12-07 7:34 GMT+01:00 Mario Schreiber <schreibermario40 at gmail.com>:

> Hello,
> I have a use case, where a vtkObject on the server implements a method like
>
> std::string doSomething(std::string arg);
>
> Now, with a proxy prx on the client for  that class, I would like to call
> the remote procedure similar to
>
> result=prx.InvokeCommand("doSomething",[arg])
>
> Is something like this possible?
> I found a very complicated workaround by first defining the arguments as
> properties, defining the result as information_only property linked to on
> of the args, then calling "UpdateVTKObjects" to push the arguments and
> finally "UpdateInformationProperties" to pull the result. Is there an
> easier solution, possible with a short example?
>
> Thank you
> Mario
>
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FIND_PACKAGE(ParaView REQUIRED)
INCLUDE(${PARAVIEW_USE_FILE})

ADD_PARAVIEW_PLUGIN(TestPlugin "1.0"
  SERVER_MANAGER_XML TestPlugin.xml
  SERVER_MANAGER_SOURCES vtkSquareFun.cxx
)

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