Problem with IsValidLink event

GoXam
1

Hi!
I’m trying to use LinkingTool to detect the linking connections between the nodes but something goes wrong when i connect the nodes. The scenario is: 2 input nodes (node 1 and node 2) and 2 output nodes (node 3 and node 4). When i connect the input node 1 to output node 3 the IsValidLink event is fired 2 times, as i have connected the input node 1 to output node 3 and also to output node 4). What could be wrong with the IsValidLink event? Thanks for your support

My code:

public class MyCustomLinkTool : LinkingTool
{
    public override bool IsValidLink(Node <b>fromNode</b>, FrameworkElement fromPort, Node <b>toNode</b>,                                                              FrameworkElement toPort)
    {
        if (!base.IsValidLink(fromNode, fromPort, toNode, toPort)) return false;

        BaseNodeData fromNodeData = fromNode.Data as BaseNodeData;
        BaseNodeData toNodeData = toNode.Data as BaseNodeData;

        //NOTE: The inputs array begins with the index 0 
        //      The outputs array beginswith the index 500
        int fromPortIndex = Convert.ToInt32(fromNode.GetPortName(fromPort)) - 500;
        int toPortIndex = Convert.ToInt32(toNode.GetPortName(toPort));

        //Check if the connected ports are of the same type and if the INPUTS ports connects with               //the OUTPUTS ports
        if (fromNodeData.InputsIOTag[fromPortIndex].GetType() == toNodeData.OutputsIOTag[toPortIndex].GetType())
        {
            Console.WriteLine("CONNECT LinkingTool: " + " From =" + fromNodeData.Key + " To = " + toNodeData.Key + " FromPort = " + fromPortIndex + " ToPort = " + toPortIndex + " Is linked = " + base.IsValidFrom(fromNode, fromPort));
        }
        else
            return false;
        return true;
    }
2

Are you talking about the situation where the user is trying to draw a new link from node 1 to node 3? And if so, are you asking about why IsValidLink is being called twice, with potential “to” nodes 3 and 4?

The reason is because of link snapping to valid ports. The linking tools have a property, LinkingBaseTool.PortGravity, which controls how far away the linking tools might snap to a potential valid port. In order to implement this functionality, the linking tools have to test all of the ports that are in the area for possibly valid links.

3

Yes Walter, my problem is exactly what you described. It’s possible to somehow i tag the nodes that i connect to avoid that the same nodes are connected twice? I think that change the LinkingBaseTool.PortGravity property could bring problems. Do you have any suggestion? Thanks

4

IsValidLink is only a predicate to check if a link is possible between two ports – it does not actually create any link or modify anything.

5

What i need is to to know the nodes that are real connected. I would like to have an event that fires always that are a new connection is established and update my code. There are some event that fires after the connection is established to avoid this “false” connections? Thanks Walter

6

The Diagram.LinkDrawn and LinkRelinked events might be what you are looking for.

Or more generally, implement a Model.Changed event handler to look for ModelChange cases that you care about.

7

Thanks Walter. That was exactly what i needed.