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

[Mario Schreiber]

Thank you for your kind reply, Utkarsh.
The C++ example clarifies many of the details that I couldn't find
explained anywhere.

I will try to wrap the missing parts in python, because we can't afford to
migrate the rest of our application to C++.
Just asking, before I waste my time with a bunch of problems that you know
in advance that cannot be solved: Is there any reason why the steps you
showed cannot be wrapped in python, or has it "just not been done, yet"?

Thanks
Mario


2016-12-13 18:54 GMT+01:00 Utkarsh Ayachit <utkarsh.ayachit at kitware.com>:

> Mario,
>
> Firstly, there's no way from Python to do what you want to do except
> using the property mechanism, since well, the goal with ParaView was
> not to provide a general purpose RPC framework. In C++, you can do
> that you want as follows:
>
> vtkSMProxy* proxy = ...
> std::string arg = ...;
> vtkClientServerStream stream;
> stream << vtkClientServerStream::Invoke
>             << VTKOBJECT(proxy)
>             << "doSomething" << arg.c_str()
>             << vtkClientServerStream::End;
>
> vtkSMSession* session = proxy->GetSession();
> session->ExecuteStream(
>    /*location*/ proxy->GetLocation(),
>   /* ignore_errores*/ false);
>
> vtkClientServerStream result = session->GetLastResult(proxy->
> GetLocation());
> if (result.GetNumberOfMessages() == 1 && result.GetNumberOfArguments(0) ==
> 1)
> {
>    std:string aresult;
>   result.GetArgument(0, 0, &aresult);
> }
>
> Utkarsh
>
>
>
> On Sun, Dec 11, 2016 at 12:01 PM, Mario Schreiber
> <schreibermario40 at gmail.com> wrote:
> > 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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