[vtkusers] java's vtkPanel does too much

[Steve M. Robbins]

Hi Jeff,

On Sat, Feb 26, 2005 at 07:12:34AM -0500, Jeff Lee wrote:

> >>In the long run, we should probably provide a base class with only 
> >>native methods which can then be extended, without the above tinkering.  
> >>Probably call it vtkNativeHook or something obvious, then vtkPanel is a 
> >>subclass.  This will require changes to the c++ code in vtkJavaAwt.h to 
> >>change the mangled jni method signatures, but it is trivial.
> >>   
> >>
> >
> >What I had in mind is for the base class to have the three native
> >methods, as well as Render() and paint().  Is that what you
> >had in mind, or is vtkNativeHook just the three native methods?
> > 
> >
> Just the 3 native methods - I believe that people may have different 
> needs from Render() and paint().  For example, if you are updating 
> pipeline data from multiple threads, you need finer control over Render 
> and paint to mutex access to the pipeline.  For the simple cases where 
> you set up a pipeline and Render, what is in vtkPanel now is fine.  For 
> those who want finer control, they either go through the gymnastics 
> above, or we provide a base class.  For example,
> 
>    * vtkNativePanel.java - base class with native methods

Does this derive from AWT Canvas?  Arguably, it doesn't have to; 
you could have vtkPanel derive from Canvas and have a vtkNativePanel
as an instance variable.

 
>    * vtkPanel.java - sublcass of vtkNativePanel, adding paint and
>      render capabilities, addNotify,removeNotify,Lock,UnLock - here is
>      what you describe as a "bare-bones" base class
> 
>    * vtkCanvas.java - layers GenericInteractor
> 
> 
> I really think that we'll never be able to write a generic Render() 
> method, because of the multithreading issue.  

I don't understand what "multithreading issue" you're driving at.
The vtkPanel.Render() method surrounds the actual rendering (rw.Render())
inside Lock()/UnLock() calls.  Isn't that enough to allow calling
vtkPanel.Render() from any thread?



 
> BTW, how you are breaking vtkCanvas?

I simply compiled and ran some of the example code from ij-plugins
(http://ij-plugins.sourceforge.net/vtk-examples).  I was just
playing around and don't have detailed notes.  I was using
VTK 4.2.  I'll try again and see if I can reproduce the problem.
I was mainly wondering whether the interactor stuff was generally
known to be broken with java; if not, I assume I have a bad
set-up in some respect.

-Steve