add: WMResizeWidget(box, W_VIEW(box)->parent->size.width, W_VIEW(box)->parent->size.height);
context: WMSetBoxExpandsToParent(WMBox *box){    WMAddNotificationObserver(resizedParent, box,			      WMViewSizeDidChangeNotification, 			      W_VIEW(box)->parent);    WMSetViewNotifySizeChanges(W_VIEW(box)->parent, True);}