interface button : widget { 
  
      button(char* p, char* options = "");
      button(widget* w, char* p, char* options = "");
      
      void text(char* s);                    // text to display
      void bitmap(char* s);                  // to display a bitmap
      
      void state(char *s);            // to change the buttons state
      
      void flash();
      char* invoke();
  
    protected:
      install(binding*,char* args);           // default binding
    };