     newConcept = nil
   }
   
+  func updateLinkViewsFor(concept: Concept) {
+    let conceptLinks = links.filter {
+      return $0.origin.identifier == concept.identifier || $0.target.identifier == concept.identifier
+    }
+    for link in conceptLinks { linkViewFor(link).needsDisplay = true }
+  }
+  
   // MARK: - CanvasLinkActions
   
   func drawLinkViews() {

  
  func pointInCanvasCoordinates(point: NSPoint) -> NSPoint
  func conceptViewFor(concept: Concept) -> ConceptView
}

// Protocol compositions

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