How to draw some figures on a editor with draw2d in a eclipse RCP? - eclipse-plugin

Question

I mean drawing somg simple shape like circle,rectangleFigure,and polylineConnectistrong.It seems that a LightweightSystem has to been constructed on a Canvas such as a Shell.And in a RCP application when I add an extension of an editor,the editor extends org.eclipse.ui.part.EditorPart by default.It has a method called createPartControl.This method has a parameter (Composite parent).
So I write the following code and it give me a Unhandled event loop exception
public void createPartControl(Composite parent) {
Shell shell = parent.getShell();
shell.open();
Display display = shell.getDisplay();
LightweightSystem lws = new LightweightSystem(shell);
IFigure panel = new Figure();
lws.setContents(panel);
RectangleFigure node1 = new RectangleFigure();
RectangleFigure node2 = new RectangleFigure();
node1.setBackgroundColor(ColorConstants.red);
node1.setBounds(new Rectangle(30, 30, 64, 36));
node2.setBackgroundColor(ColorConstants.blue);
node2.setBounds(new Rectangle(100, 100, 64, 36));
PolylineConnection conn = new PolylineConnection();
conn.setSourceAnchor(new ChopboxAnchor(node1));
conn.setTargetAnchor(new ChopboxAnchor(node2));
conn.setTargetDecoration(new PolygonDecoration());
Label label = new Label("Midpoint");
label.setOpaque(true);
label.setBackgroundColor(ColorConstants.buttonLightest);
label.setBorder(new LineBorder());
conn.add(label, new MidpointLocator(conn, 0));
panel.add(node1);
panel.add(node2);
panel.add(conn);
while (!shell.isDisposed ()) {
if (!display.readAndDispatch ())
display.sleep ();
}
}
So how to solve this problem and how to draw these figures on the editor?

Answer 1

As you want to draw inside the editor, you don't need to create new Shell nor dispatch events from the event queue as you would do in a standalone SWT application; just create a Canvas and draw into it. This should help you:
public void createPartControl(Composite parent) {
Canvas canvas = new Canvas(parent, SWT.NONE);
LightweightSystem lws = new LightweightSystem(canvas);
IFigure panel = new Figure();
lws.setContents(panel);
[...]
panel.add(node1);
panel.add(node2);
panel.add(conn);
}