Creating a non-rectangular shell to simulate transparency

[Java Tip]

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.Image;
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 Snippet180 {

  public static void main(String[] args) {
    Display display = new Display();
    final Image image = display.getSystemImage(SWT.ICON_WARNING);
    // Shell must be created with style SWT.NO_TRIM
    final Shell shell = new Shell(display, SWT.NO_TRIM | SWT.ON_TOP);
    shell.setBackground(display.getSystemColor(SWT.COLOR_RED));
    // define a region
    Region region = new Region();
    Rectangle pixel = new Rectangle(0, 0, 1, 1);
    for (int y = 0; y < 200; y += 2) {
      for (int x = 0; x < 200; x += 2) {
        pixel.x = x;
        pixel.y = y;
        region.add(pixel);
      }
    }
    // define the shape of the shell using setRegion
    shell.setRegion(region);
    Rectangle size = region.getBounds();
    shell.setSize(size.width, size.height);
    shell.addPaintListener(new PaintListener() {
      public void paintControl(PaintEvent e) {
        Rectangle bounds = image.getBounds();
        Point size = shell.getSize();
        e.gc.drawImage(image, 0, 0, bounds.width, bounds.height, 10,
            10, size.x - 20, size.y - 20);
      }
    });
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    region.dispose();
    display.dispose();
  }
}