Sometimes it is necessary to place the connection points
on a rectangle smaller or larger than the bounding box, possibly in
a nonsymmetric way. For instance, it can happen when labels are displayed
below or above nodes.
You can modify the position of the connection points
of the links by providing a class that implements the ILinkConnectionBoxProvider. Use the method setLinkConnectionBoxInterface.
To set a link connection box provider in Dojo, call:
dojo.declare("MyLinkConnectionBoxProvider", ibm_ilog.graphlayout.ILinkConnectionBoxProvider, { getBox : function(graphModel, node) { var rect = graphModel.boundingBox(node); // modify rect... return rect; }, getTangentialOffset : function(graphModel, node, nodeSide) { var offset = 0; // modify offset according to nodeSide... return offset; } }); treeLayout.setLinkConnectionBoxInterface(new MyLinkConnectionBoxProvider());
The link connection box interface provides each node
with a link connection box and a tangential shift offset that defines
how much the connection points are “shifted” tangentially
depending on which side the links connect.
The following figure illustrates the effects of customizing
the connection box when the connector style is evenly spaced.

Effect of connection box interface
On the left is the result without any connection box
interface. The middle picture shows the effect if the connection box
interface returns the dashed rectangle for the blue node but the tangential
offset at all sides of the node is 0. Notice that the outgoing links
are spaced according to the dashed rectangle, which appears too wide
for the blue node in this situation. The picture on the right shows
the effect of the connection box interface if, in addition, a positive
tangential offset was specified for the bottom side and a negative
offset was specified for the left side of the blue node.