[vtkusers] Nonblocking vtkRenderWindowInteractor

[Clinton Stimpson]

Quoting Budd Hirons <budd at nanacatl.net>:

> I like it, I have one question : when you close one of your rendering 
> windows the interactor does a PostQuitMessage under win32 (and I 
> guess it must do a similar thing under the other platforms you 
> support)

Nope, just the vtkWin32RenderWindowInteractor behaves this way.

> and kills the whole program, how do you stop this in a cross platform 
> way without overriding or modifying all the interactor classes?

Without writing Windows specific code -- Add an observer to the interactor to
get vtkCommand::ExitEvent.  PostQuitMessage() won't be called if there is
that observer.

Clint