anchor.diff:        save hist
   
     onMouseDown: (ev) -> 
  +    return if fetch('slider').is_moving
       ev.stopPropagation()
   
       hist = fetch('histogram')
  
positive.code:         save @local
  
    onMouseLeave: (ev) -> 
      @local.mouse_opinion_value = null
      save @local
  
    onMouseUp: (ev) -> 
      hist = fetch('histogram')     
      
      if hist.dragging
  
negative.code: 
      # We save the slider's position to the server only on mouse-up.
      # This way you can drag it with good performance.
      if your_opinion.stance != slider.stance
        your_opinion.stance = slider.stance
        save your_opinion
        window.writeToLog 
          what: 'move slider'
  