@Override
		public void handleEvent (Event event) {
			switch (event.type) {
				case SWT.MouseDown:
					point = new Point (event.x, event.y);
					break;
				case SWT.MouseMove:
					if (point == null) return;
					int deltaX = point.x - event.x, deltaY = point.y - event.y;
					if (Math.abs (deltaX) < JITTER && Math.abs (deltaY) < JITTER) {
						return;
					}
					tracker = new Tracker (display, SWT.NONE);
					Rectangle rect = display.map (shell, null, shell.getClientArea ());
					rect.x -= deltaX;
					rect.y -= deltaY;
					tracker.setRectangles (new Rectangle [] {rect});
					tracker.open ();
					//FALL THROUGH
				case SWT.MouseUp:
					point = null;
					if (tracker != null) {
						tracker.dispose ();
						tracker = null;
					}
					break;
			}
		}