In this section you will learn how to programmatically assign a rule to an element (VisualNode or VisualEdge).

Below we add a new rule named “nrule2” to rule definition file rule.xml. This rule specifies a resizeable node.

...
    
<list name="Rule">
  <attribute name="Name" type="String" value="nrule2"/>
  <attribute name="Type" type="String" value="NodeRule"/>
  <list name="Properties">
    <attribute name="Deletable" type="Boolean" value="false"/>
    <attribute name="Moveable" type="Boolean" value="true"/>
    <attribute name="Selectable" type="Boolean" value="true"/>
    <attribute name="Resizable" type="Boolean" value="true"/>
    
    ...
    
  </list>
</list>

...

In this example, we do not want all our visual nodes to be resizeable, just the root one. This requires us to retrieve that root node (variable nodeA is holding this root node in the graph model), get the corresponding VisualNode object and then apply our new rule “nrule2” to it. The following code snippet reflects these steps.

// retrieve the first node of the graph
VisualNode vNodeA= 
    graphView.getVisualNodeByID(nodeA.getID());

// apply the previously defined rule 
vNodeA.setRule("NormalNodeRule");

Adding these lines of code will result in a resizeable root node. When you get around to reading the javadocs, you will notice that rules can be set for any VisualGraphObject instance!