anchor.diff:                  top: -15
                   cursor: 'col-resize'
   
  -
             DIV 
               style:
                 height: HISTOGRAM_HEIGHT + region_selection_vertical_padding
  
positive.code:     # whether to show the shaded opinion selection region in the histogram
      draw_selection_area = !hist.selected_opinion && 
                              @root.proposal_mode == 'results' &&
                              ((!@local.touched && hist.selected_opinions) || 
                                (@local.mouse_opinion_value && !@local.hoving_over_avatar)) 
  
      DIV 
        className: 'histogram'
  
negative.code: #   * If a region is selected, clicking anywhere except within the 
  #     decision board will deselect the region.
  #
  # Note that for mobile, region resizing is disabled, and the selection 
  # changes on touch move rather than mousemove.
  # 
  ##
  # Selected region background
  #   * A selection region background follows the mouse in the histogram if:
  