     for v, i in sorted
       console.log "**#{v.key} constraints**" if debug
       k = v.key; dock = fetch k
-      previous_calculated_y = docker.component_history[k].previous.calculated_y
+      previous_calculated_y = dockingStation.component_history[k].previous.calculated_y
 
       # START
       console.log "\tSTART: #{k} >= #{v.start}, strong" if debug

        is_docked = false 
      else
        dimensions =  if fetch(v.key).docked
                        docker.component_history[v.key].on_dock
                      else 
                        {height: v.height, jut_above: v.jut_above}

        is_docked = docker.viewport.top + y_stack + dimensions.jut_above >= v.start

      if is_docked
        y_stack += dimensions.height

      x = 0
    else
      # Fixed positioning is relative to the viewport, not the document
      y -= dockingStation.viewport.top 

      # Adjust for horizontal scroll for fixed position elements because they don't 
      # move with the rest of the content (they're fixed to the viewport). 
