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• YifanHu Multilevel

This How To shows how to create a new layout algorithm in Gephi.

Please look at Plugin Quick Start to know how to create a new Netbeans Module. When you have your plugin module, that we will call MyLayout, you can start this tutorial.

Add LayoutAPI, GraphAPI (UtilitiesAPI for @ServiceProvider see below and LookupAPI since it's almost always useful) modules as dependencies for your plugin module MyLayout. See How To Set Module Dependencies.

• Layout Builder provides information about the layout algorithm and is responsible for creating your Layout algorithm instances. All Layout algorithms should have their own builder.
• Create a new builder class, for instance MyLayoutBuilder that implements LayoutBuilder.
• The builder interface is requesting a LayoutUI object. Create an inner or anonymous class that implements LayoutUI.
• Add @ServiceProvider annotation to your builder class. Add the following line before MyLayoutBuilder class definition, as shown below:

import org.openide.util.lookup.ServiceProvider;
 
@ServiceProvider(service = LayoutBuilder.class)
public class MyLayoutBuilder implements LayoutBuilder {
...

Create a new class that implements Layout. This is the place the algorithm belongs.

Methods canAlgo(), initAlgo(), goAlgo() and endAlgo() are the logic of the algorithm. But the algorithm is manipulating a graph, so where is this graph? The graph can be get from the GraphModel, which is injected through the setGraphModel() method (fill setGraphModel() with this.graphModel = graphModel;). The system always sets this graph model before initAlgo() is called.

Add the graph model as a new private field of your class. In your goAlgo() method, add the following code to get the current visible graph:

graph = graphModel.getHierarchicalGraphVisible();

Your algorithm may have settings and properties that users may control. To be visible and editable in the Layout UI, properties need to be properly defined.

Let's say you have a float speed parameter that you want to expose. That is how to create the appropriate LayoutPropery:

LayoutProperty mySpeedProperty = LayoutProperty.createProperty(
    this, 
    Float.class,
    "Speed"
    "Category",
    "A short description what is this propery doing and how users may modify it",
    "getSpeed", 
    "setSpeed");

Note that you need to create proper getter and setter for each property you want to expose.

A special mechanism is available if you need to store temporary objects in nodes. In the following example, we will create a new type of layout data which stores a dx and dy value.

Create a new MyLayoutData class that implements LayoutData and add two floats dx and dy. How to init? Place the following code at the beginning of goAlgo():

for (Node n : nodes) {
   if (n.getNodeData().getLayoutData() == null || !(n.getNodeData().getLayoutData() instanceof MyLayoutData)) {
      n.getNodeData().setLayoutData(new MyLayoutData());
   }
}

That ensure you have a layout data object for each of your nodes.

Properties can be basic types like Boolean, Float etc. If you want to expose custom types, for instance date, you can provide a PropertyEditor class when building the property.

Note that a custom PropertyEditor class has been created for AttributeColumn in the AttributeColumnPropertyEditor module. Add this module as a new dependency.