code: public List<ActionConstraint> getActionConstraints(final WButton button) {
  		List<ActionConstraint> constraints = getComponentModel().actionConstraints.get(button);
  		return constraints == null ? null : Collections.unmodifiableList(constraints);
  	}
docs: Retrieves the constraints for the given action.
  
  @param button the button to retrieve the constraints for.
  @return the constraints for the given action, or null if there are no constraints.