   func clickOnConceptView(conceptView: ConceptView, point: NSPoint)
   func dragFromConceptView(conceptView: ConceptView, point: NSPoint)
   func releaseMouseFromConceptView(conceptView: ConceptView, point: NSPoint)
+  func updateLinkViewsFor(concept: Concept)
 }
 
 protocol CanvasLinkActions {

    if let linkView = linkViews[link.identifier] {
      linkView.needsDisplay = true
    } else {
      let linkView = LinkView(link: link, canvas: self)
      addSubview(linkView)
      linkViews[link.identifier] = linkView

    sprint("drag from conceptView \(conceptView.concept.identifier) to \(point)")
    arrowOriginPoint = conceptView.concept.point
    arrowTargetPoint = point
    updateLinkViewsFor(conceptView.concept)
    needsDisplay = true
  }
  
