static final int POINTS = 11;

  public static void main(String[] args) {
    final Point center = new Point(0, 0);
    final int[] radial = new int[POINTS * 2];

    final Display display = new Display();
    final Color black = display.getSystemColor(SWT.COLOR_BLACK);

    final Shell shell = new Shell(display, SWT.NO_TRIM);
    shell.setBackground(black);
    shell.setSize(200, 200);

    Rectangle bounds = shell.getClientArea();

    center.x = bounds.x + bounds.width / 2;
    center.y = bounds.y + bounds.height / 2;

    int pos = 0;
    for (int i = 0; i < POINTS; ++i) {
      double r = Math.PI * 2 * pos / POINTS;
      radial[i * 2] = (int) ((1 + Math.cos(r)) * center.x);
      radial[i * 2 + 1] = (int) ((1 + Math.sin(r)) * center.y);
      pos = (pos + POINTS / 2) % POINTS;

    }

    Listener listener = new Listener() {
      int offsetX = 0, offsetY = 0;

      public void handleEvent(Event e) {
        switch (e.type) {
          case SWT.MouseDown:
            if (e.button == 1) {
              offsetX = e.x;
              offsetY = e.y;
            }
            break;
          case SWT.MouseMove:
            if ((e.stateMask & SWT.BUTTON1) != 0) {
              Point pt = shell.toDisplay(e.x, e.y);
              pt.x -= offsetX;
              pt.y -= offsetY;
              shell.setLocation(pt);
            }
            break;
          case SWT.KeyDown:
            shell.dispose();
            break;
        }
      }
    };
    
    shell.addListener(SWT.MouseDown, listener);
    shell.addListener(SWT.MouseMove, listener);
    shell.addListener(SWT.KeyDown, listener);

    Region region = new Region(display);
    region.add(radial);

    shell.setRegion(region);
    shell.open();

    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    region.dispose();
    display.dispose();
  }

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.MouseEvent;
import org.eclipse.swt.events.MouseListener;
import org.eclipse.swt.events.MouseMoveListener;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.graphics.Region;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class RingShell {
  int[] createCircle(int radius, int centerX, int centerY) {
    int[] points = new int[360 * 2];
    for (int i = 0; i < 360; i++) {
      points[i * 2] = centerX + (int) (radius * Math.cos(Math.toRadians(i)));
      points[i * 2 + 1] = centerY + (int) (radius * Math.sin(Math.toRadians(i)));
    }
    return points;
  }

  Point originalPosition = null;

  public RingShell() {
    final Display display = new Display();
    final Shell shell = new Shell(display, SWT.NO_TRIM | SWT.ON_TOP);
    shell.setBackground(display.getSystemColor(SWT.COLOR_DARK_MAGENTA));
    Region region = new Region();
    region.add(createCircle(100, 100, 100));
    region.subtract(createCircle(50, 100, 100));
    shell.setRegion(region);
    // Make the shell movable by using the mouse pointer.
    shell.addMouseListener(new MouseListener() {
      public void mouseDoubleClick(MouseEvent e) {
        shell.dispose(); // Double click to dispose the shell.
      }

      public void mouseDown(MouseEvent e) {
        originalPosition = new Point(e.x, e.y);
      }

      public void mouseUp(MouseEvent e) {
        originalPosition = null;
      }
    });
    shell.addMouseMoveListener(new MouseMoveListener() {
      public void mouseMove(MouseEvent e) {
        if (originalPosition == null)
          return;
        Point point = display.map(shell, null, e.x, e.y);
        shell.setLocation(point.x - originalPosition.x, point.y - originalPosition.y);
        System.out.println("Moved from: " + originalPosition + " to " + point);
      }
    });
    Rectangle regionBounds = region.getBounds();
    shell.setSize(regionBounds.width, regionBounds.height);
    shell.open();

    // Set up the event loop.
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch()) {
        // If no more entries in event queue
        display.sleep();
      }
    }
    display.dispose();
    region.dispose();
  }

  public static void main(String[] args) {
    new RingShell();
  }
}