Initial location of programmatically created shape in DSL Tools

Question

How can I setup the initial position of an element (Element A) which I create programmatically? The creation of that element occurs when the user of the DSL makes a connection between two other elements (Element B). Instead of drawing a connector between the two B's, I let the DSL connect a B with a newly created A and the A with the other B: B----A----B. I have this working by using a custom connection builder with the following Connect() method:

public static void Connect(ModelElement sourceElement, ModelElement targetElement)
{
    B source;
    B target;
    A a;

    source = sourceElement as B;
    target = targetElement as B;

    a = new A(source.Partition);   
    source.AElements.Add(a);
    a.B= target;
}

I have tried to set the location of Element A with an AddRule as suggested here: http://social.msdn.microsoft.com/forums/en-US/vsx/thread/225836cb-9d86-4035-922c-1e21cc373a62 by Pedro Silva, but the shape.Location = ...; line seems to be ignored. Only when I save and re-open the diagram, the shape is moved to the new location.

I also tried to solve my problem by overriding the OnShapeInserted() method of Element A. This seems to work, but then I have to use an extra transaction and thus I get an extra (unwanted) undo entry when using the DSL.

Is there a way to force the shape to use the new location in my AddRule try or is there a way to hide the extra undo entry when overriding OnShapeInserted()?

Answer 1

Normally, shape creation and placement is done automatically by a process called view fixup. However, you can explicitly create and place shapes if necessary. The following code snippet creates a new element and shape every time the user double-clicks on the design surface.

partial class TestMinLanguage1Diagram
{
    public override void OnDoubleClick(Microsoft.VisualStudio.Modeling.Diagrams.DiagramPointEventArgs e)
    {
        base.OnDoubleClick(e);
        AddAndPositionShapeAndElement(this, e.MousePosition);
    }

    private static void AddAndPositionShapeAndElement(TestMinLanguage1Diagram diagram, PointD createLocation)
    {

        using (Transaction t = diagram.Store.TransactionManager.BeginTransaction("Add and position elements"))
        {

            ExampleModel rootElement = diagram.ModelElement as ExampleModel;
            
            // Add a new element and link it to the model
            ExampleElement newElement = new ExampleElement(rootElement.Partition);
            rootElement.Elements.Add(newElement);

            // Create a new shape that represents the new element,
            // associate it with the new element, 
            // size it, position it and link it to the diagram.
            ExampleShape newShape = new ExampleShape(diagram.Partition);
            newShape.ModelElement = newElement;
            newShape.AbsoluteBounds = new Microsoft.VisualStudio.Modeling.Diagrams.RectangleD(createLocation, new SizeD(1,1));
            diagram.NestedChildShapes.Add(newShape);
            
            t.Commit();
        }

    }

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