@Override
 public void mouseReleased(MouseEvent e) {
   isLeftButtonPressed = false;
   if (e.getButton() == MouseEvent.BUTTON3) {
     ((DrawPad) parent).getSelectedLayer().undoLastDraw();
   } else if ((e.getButton() == MouseEvent.BUTTON1) && ((DrawPad) parent).isRubberMode()) {
     ((DrawPad) parent).getSelectedLayer().eraseEnd();
   }
   parent.repaint();
 }