public void setGrayed (boolean value) {
	checkWidget ();
	if ((parent.getStyle () & SWT.CHECK) == 0) return;
	if (grayed == value) return;
	grayed = value;
	if ((parent.getStyle () & SWT.VIRTUAL) != 0) cached = true;

	if (isInViewport ()) {
		Rectangle bounds = getCheckboxBounds ();
		parent.redraw (bounds.x, bounds.y, bounds.width, bounds.height, false);
	}
}