anchor.diff:  part of controls_and_panels;
   
   abstract class Base{
  -  
  +
     static const String CLASS = 'cnp-base';
  -  static const String FILL = 'fill';
  +  static const String FILL = 'cnp-fill';
     static const String CNP_STAGING_ELEMENT_ID = 'cnp-staging-element-id';
  -  
  +
     static final DivElement _cnpStagingElement = new DivElement()
     ..id = CNP_STAGING_ELEMENT_ID
     ..style.position = 'absolute'
  
positive.code:   void fill(){
      html.classes.add(FILL);
    }
    
    void unfill(){
      html.classes.remove(FILL);
    }
    
    void addClass(dynamic cssClass){
      if(cssClass is EnumValue){
        cssClass = cssClass.toString();
      }
      html.classes.add(cssClass);
    }
    
    void addClasses(List<dynamic> cssClasses){
      cssClasses.forEach((cssClass){
        addClass(cssClass);
      });
    }
    
    void removeClass(dynamic cssClass){
      if(cssClass is EnumValue){
        cssClass = cssClass.toString();
      }
      html.classes.remove(cssClass);
    }
    
    void removeClasses(List<dynamic> cssClasses){
      cssClasses.forEach((cssClass){
        removeClass(cssClass);
      });
    }
    
    void setSize(String width, String height, {String minWidth, String maxWidth, String minHeight, String maxHeight}){
      html.style
      ..width = width
      ..minWidth = minWidth == null? width: minWidth
      ..maxWidth = maxWidth == null? width: maxWidth
  
negative.code:   ..style.border = '0'
    ..style.padding = '0'
    ..style.overflow = 'hidden';
  
    static bool _fillByDefault = false;
  
    static void setFillByDefault(){
      _fillByDefault = true;
    }
  
    static void setShrinkByDefault(){
      _fillByDefault = false;
    }
  
    final DivElement html = new DivElement();
  
    CssStyleDeclaration get style => html.style;
  
    Base(){
      _baseStyle.insert();
      addClass(CLASS);
      stage();
      if(_fillByDefault){
        fill();
  