Re: Java multi-thread and model Observer

Hi Jean-Max,

I'm not sure to follow all the details of your implementation or why you
still have the use of a Timer.
The only things that you need to worry about is that any rendering action
(addActor/removeActor, update when actor connected, render) MUST BE in the
EDT.

HTH,

Seb

On Thu, Feb 21, 2019 at 2:19 AM Jean-Max Redonnet <[email protected]>
wrote:

> Hello everyone !
>
> I'm using vtk throught its java wrapper and I'm setting up a versatile
> viewer that can display an existing model and update display when this
> model is updated (and it will be continously updated).
>
> My Model is built around few classes: VtkObject that is the ancestor of
> many other classes like VtkSurface, VtkCurve, etc... and VtkModel that
> basically contains a list of VtkObjects and maintain Listeners. All these
> classes are of my own (please note uppercase "V" on VtkObject)
>
>
> public class VtkObject{
>     protected final PropertyChangeSupport pcs = new
> PropertyChangeSupport(this);
>     protected List<vtkActor> actors = new ArrayList<vtkActor>();
>     ...
> }
>
> public class VtkSurface extends VtkObject {
>     private vtkActor surfActor;
>     ...
> }
>
> public class VtkModel implements PropertyChangeListener{
>     protected List<VtkObject> objects;
>     protected PropertyChangeSupport support;
>     ...
> }
>
> For the viewer itself I wrote a VtkPanel that is mostly inspired by the
> example provided by Sébastien Jourdain (
> https://github.com/Kitware/VTK/blob/master/Wrapping/Java/vtk/sample/Demo.java
> )
>
> I just make this panel model-aware implementing PropertyChangeListener:
>
>     @Override
>     public void propertyChange(PropertyChangeEvent evt) {
>         if (evt.getPropertyName() == "AddedObject") {
>             System.out.println("Added Object");
>             VtkObject o = (VtkObject) evt.getNewValue();
>             if(o.getActors().size()>0)
>                 exec.submit(new PipelineBuilder(o));
>         }
>         if (evt.getPropertyName() == "UpdatedObject") {
>             System.out.println("Updated Object");
>             VtkObject o = (VtkObject) evt.getNewValue();
>             if(o.getActors().size()>0)
>                 exec.submit(new PipelineBuilder(o));
>         }
>     }
>
> and slithly modify PipelineBuilder to make it able to manage VtkObjects
> that may contain several vtkActors
>
>     public class PipelineBuilder implements Callable<vtkActor> {
>         private int counter;
>         private List<vtkActor> actors;
>
>         public PipelineBuilder(VtkObject o) {
>             actors = o.getActors();
>             counter = 0;
>         }
>
>         @Override
>         public vtkActor call() throws Exception {
>             counter++;
>             if (counter < actors.size() + 1)
>                 return actors.get(counter - 1);
>             return null;
>         }
>     }
>
> Also, workers are setup to continously search for new actors:
>
>     private void setupWorkers() {
>         // Add actor thread: Consume the working queue and add the actor
> into
>         // the render inside the EDT thread
>         final AddActorRunnable adderRunnable = new AddActorRunnable();
>         adderRunnable.setRenderer(panel3d);
>         new Thread() {
>             public void run() {
>                 while (true) {
>                     try {
>                         adderRunnable.setActor(exec.take().get());
>                         SwingUtilities.invokeAndWait(adderRunnable);
>                         panel3d.repaint();
>                     } catch (InterruptedException e) {
>                         return;
>                     } catch (ExecutionException e) {
>                         e.printStackTrace();
>                     } catch (InvocationTargetException e) {
>                         e.printStackTrace();
>                     }
>                 }
>             };
>         }.start();
>     }
>
>
> Here is the test class I use:
>
> public class TestVtkPanel {
>     public VtkModel model;
>
>     public TestVtkPanel() {
>         SwingUtilities.invokeLater(new Runnable() {
>             public void run() {
>                 model = getModel();
>                 VtkPanel panel = new VtkPanel();
>                 model.addPropertyChangeListener(panel);
>
>                 JButton exitBtn = new JButton("Quitter");
>                 exitBtn.addActionListener(new ActionListener() {
>
>                     public void actionPerformed(ActionEvent e) {
>                         System.exit(0);
>                     }
>                 });
>                 JFrame f = new JFrame("Vtk Viewer");
>                 f.getContentPane().setLayout(new BorderLayout());
>                 f.getContentPane().add(panel, BorderLayout.CENTER);
>                 f.getContentPane().add(exitBtn, BorderLayout.SOUTH);
>
>                 f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
>                 f.setSize(800, 600);
>                 f.setVisible(true);
>                 f.validate();
>
>                 panel.startWorking(model);
>
>                 new Thread(new Runnable() {
>                     public void run() {
>                         updateModel();
>                     }
>                 }).start();
>
>             }
>         });
>
>     }
>
>
>     ...
>   }
>
>
>
> All this stuff works fine, but few questions remains.
>
> Is this way to do thing is the best for what I'm trying to achieve ? If a
> vtk guru can give a look to my code, it would be gratefully appreciated.
> Furthermore inside the VtkPanel constructor I tried to put the vtkPanel
> panel3d outside of the Timer but that do not work.
>
>     new Timer(1000, new ActionListener() {
>
>             public void actionPerformed(ActionEvent e) {
>                 if (nbSeconds++ < 1) {
>                     panel3d.resetCamera();
>                 }
>                 // Run GC in local thread (EDT)
>             ...
>      }
>
> I can't figure out why. Any hint on this point may help me to understand
> multithreading.
>
> Thanks for your help.
>
> jMax
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