From: Aureliano Buendia <saveez@...>
Date: 2006-11-10T02:09:20+09:00
Subject: Ruby and threads: a VTK example

Hi,

There is a ruby wrapper available for vtk which works, more or less, 
fine. For those who are not familiar with vtk, it is avisualisation 
library written in c++ and the output is a native window showing some 
interactive OpenGL graphics.

The VTK code usually ends with:

iren = Vtk::RenderWindowInteractor.new
iren.start()

Here is where the problem comes: iren.start() starts a new thread in 
c++, while, I am trying to run the script in irb and interactively 
change the objects properties and see the live results in the OpenGL 
window. Unfortunately, after iren.start() ruby goes to a deep sleep. 
This is the irb output:

>> 
?> iren.Start()

which obviously does not let me to enter any more commands unless I 
close the window:

=> nil
>> 

which is too late for manipulating objects interactively.

It is surprising when a multi-threaded c++ library is single-threaded 
after wrapping to ruby. If this does something have to do with ruby not 
supporting native threads, perhaps it is a big sacrifice for 
portability.

What is the best way to have irb command line, while also having the 
graphics rendering window?

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