Some more problems/questions:
1. Anchor points are always shown in NodeListView. I think it would be better to hide them in NodeListView and show them on the Diagram.
2. When Diagram.ShowAnchors is set to Auto, anchors appear when mouse approaches the anchor point from the right and from the bottom, but not from the left or from the top. This makes it very awkward to connect links to anchor points located on the top and left sides of a shape. I think that absolute distance from the mouse to the anchor point should be checked.
3. Is it possible to make anchor marks smaller or change their color? I can subclass a shape or a diagram if that's necessary.

Thanks.

I hope that this picture illustrates the problem:



Basically, the behavior is not symmetrical. The anchors appear early when the mouse pointer is approaching the shape from the right and from the bottom. But the mouse pointer has to be quite deep (!) inside the shape for the anchors to appear when it is approaching from the left and from the top.

Any ideas?

Yes, I can reproduce the problem with standard Ellipse.

ShapeNode node = new ShapeNode();
            node.Shape = Shapes.Ellipse;
            node.AnchorPattern = new AnchorPattern(new AnchorPoint[] {
                new AnchorPoint(50, 0),
                new AnchorPoint(50, 100),
                new AnchorPoint(0, 50),
                new AnchorPoint(100, 50)});
            workflowDiagram.Nodes.Add(node);
 

Diagram definition in XAML:

<my:Diagram Width="Auto" Height="Auto" AllowInplaceEdit="False" Name="workflowDiagram" ShowGrid="True" AlignToGrid="True" LinkCreating="workflowDiagram_LinkCreating" RouteLinks="True" GridStyle="Lines" GridColor="#1B000000" GridPointSize="1" GridSizeY="10" GridSizeX="10" LinkCrossings="Arcs" LinkStyle="Cascading" UndoEnabled="True" ItemAdded="workflowDiagram_ItemAdded" AdjustmentHandlesSize="8" KeyDown="workflowDiagram_KeyDown" SelectionChanged="workflowDiagram_SelectionChanged" NodeDoubleClicked="workflowDiagram_NodeDoubleClicked" NodeModified="workflowDiagram_NodeModified"  />