SWT(JFace) 체험의 원형(반지형)

package swt_jface.demo1; 
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); 

shell.addMouseListener(new MouseListener() { 
public void mouseDoubleClick(MouseEvent e) { 
display.dispose(); 
} 
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(); 
while (!shell.isDisposed()) { 
if (!display.readAndDispatch()) { 
display.sleep(); 
} 
} 
display.dispose(); 
region.dispose(); 
} 

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