recognize if we click on a link

EduNetworkBuilder/Network.cs

@@ -501,6 +501,21 @@ namespace EduNetworkBuilder
             }
             return null;
         }
+
+        public NetworkLink LinkAtPosition(Point NetworkLocation)
+        {
+            NetworkLink tLink;
+            foreach (NetworkComponent tItem in NetComponents)
+            {
+                if (tItem is NetworkLink)
+                {
+                    tLink = (NetworkLink)tItem;
+                    if (tLink.AtLocation(NetworkLocation))
+                        return tLink;
+                }
+            }
+            return null;
+        }
         public List<NetworkDevice> DevicesInRectangle(Rectangle area)
         {
             NetworkDevice tDevice;

EduNetworkBuilder/NetworkBuilder.cs

@@ -1233,6 +1233,10 @@ namespace EduNetworkBuilder
             Point CenteredLocation = myNetwork.clickedPosCentered(e.Location);
             Point ClickLocation = myNetwork.clickedPos(e.Location);
             NetworkDevice ReleasedOn = myNetwork.ItemAtPosition(ClickLocation);
+            NetworkLink ReleasedOnLink = null;
+            if(ReleasedOn == null)
+                ReleasedOnLink = myNetwork.LinkAtPosition(ClickLocation);
+            
             LastBackgroundImage = null;
             pbNetworkView.Image = null; //erase old highlight area
             LastMouseMovePos = new Point(-1, -1);

EduNetworkBuilder/NetworkLink.cs

@@ -320,6 +320,47 @@ namespace EduNetworkBuilder
             return usedLinks;
         }
 
+        public bool AtLocation(Point NetworkPoint)
+        {
+            Network myNet = NB.GetNetwork();
+            NetworkDevice Src = myNet.HostMatchingHostNicID(SrcNic);
+            NetworkDevice Dst = myNet.HostMatchingHostNicID(DstNic);
+            int Slop = 10;
+            int AutoWin = Slop * 2;
+            //Draw a line between them
+            if (Src == null || Dst == null)
+                return false;
+
+            Point sPoint = Src.GetCenter();
+            Point dPoint = Dst.GetCenter();
+            Rectangle SlopRec = new Rectangle(
+                Math.Min(sPoint.X, dPoint.X) - Slop,
+                Math.Min(sPoint.Y, dPoint.Y) - Slop,
+                Math.Abs(sPoint.X - dPoint.X) + (Slop * 2),
+                Math.Abs(sPoint.Y - dPoint.Y) + (Slop * 2));
+            Rectangle ActualRec = new Rectangle(
+                Math.Min(sPoint.X, dPoint.X),
+                Math.Min(sPoint.Y, dPoint.Y),
+                Math.Abs(sPoint.X - dPoint.X),
+                Math.Abs(sPoint.Y - dPoint.Y));
+            if (SlopRec.Contains(NetworkPoint))
+            {
+                if (ActualRec.Width < AutoWin || ActualRec.Height < AutoWin) return true; //we are close enough
+                //We are inside it.  Now to figure out if we are somewhere along the line
+                Rectangle smallrec = new Rectangle(Math.Min(sPoint.X, dPoint.X),
+                               Math.Min(sPoint.Y, NetworkPoint.Y),
+                               Math.Abs(sPoint.X - NetworkPoint.X),
+                               Math.Abs(sPoint.Y - NetworkPoint.Y));
+                double deltax = smallrec.Width / (double)ActualRec.Width;
+                double deltay    = smallrec.Height / (double)ActualRec.Height;
+                double TrueDelta = Math.Abs(Math.Abs(deltax) - Math.Abs(deltay));
+                if (TrueDelta > .15) return false;
+                return true;
+            }
+            return false;
+        }
+
+
         /// <summary>
         /// Have the packet traverse the network
         /// </summary>