def command *args, &block
       if event? :PRESS
         bind :PRESS, *args, &block
       else
         bind :CHANGED, *args, &block
       end
     end
def command *args, &block
       if event? :PRESS
         bind :PRESS, *args, &block
       else
         bind :CHANGED, *args, &block
       end
     end
a general method for all widgets to override with their favorite or most meaninful event
 Ideally this is where the block in the constructor should land up.
 @since 1.5.0    2011-11-21