[news.eclipse.tools.gef] Layout listeners and calculate preferred size

[Brad Reynolds <bradleyjames@xxxxxxxxx>]

I have 4 viewports and each have their own layout, of course.  I have 
the need for figures in each viewport to determine the size of figures 
in other viewports.  Previously I had done this with syncing of the 
layouts by performing an evaluation after layout had occurred.  I 
decided to get rid of the syncing and to evaluate the sizes of all 
figures at once and then push the needed information down to the 
individual layouts.  So when the figures are invalidated, my aggregator 
is invalidated and when layout is invoked on any of the layouts my 
aggregator receives the request and if it's invalid as well it evaluates 
the sizes and pushes the data down to it's layouts.  This works great 
except for when calls are made to layout.calculatePreferredSize().  In 
my calculate method I call the internal layout.  This doesn't fire 
events to the listeners thus my aggregator couldn't run.  I was trying 
to keep dependencies on the aggregator out of my layout, it was just 
simpler that way.  Does anyone see a way to handle this without creating 
any dependencies?  The way I've hacked it up now is that on my figure I 
overrode layout and made it public.  So in calculate preferred size I 
check to see if the figure is an instance of my figure and then call 
layout().  This allows for the LayoutNotifier to be invoked and the 
event fires.

The other thing I wanted to ask about is the fact that if I add a layout 
listener to a figure and then set the layout the listeners don't fire. 
This seems a little odd to me.  The reason for it is that the listeners 
are attached to the internaly LayoutNofitifer and aren't stored at the 
figure level.  So when a layout is set it seems to lose all listeners. 
I would understand this behavior if I was attaching the listeners to an 
individual layout but if I'm attaching at the figure level I don't care 
about the layout instance.  This can be seen with the following snippet:

public class LayoutListenerTest {
	void run() {
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setLayout(new FillLayout());
		
		FigureCanvas canvas = new FigureCanvas(shell);
		IFigure content = new Figure();
		canvas.setContents(content);

		content.addLayoutListener(new LayoutListener.Stub() {
			public boolean layout(IFigure container) {
				System.out.println("layout"); //$NON-NLS-1$
				return false;
			}
		});
		content.setLayoutManager(new StackLayout());

		IFigure rect = new RectangleFigure();
		content.add(rect);
		
		shell.open();
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch())
				display.sleep();
		}

		display.dispose();
	}

	public static void main(String[] args) {
		new LayoutListenerTest().run();
	}
}

If I were to move the attaching of the listener to after setting the 
layout I receive notifications.

Thanks,
Brad