To define your own eclipse editor you need to follow these steps:

• Extend EditorPart
• Define a RootEditPart, GraphicalViewer and an EditDomain
• Create the model in createPartControl
• Set the viewer’s RootEditPart, add the EditDomain to the viewer and create its control
• Set the viewer’s EditPartFactory
• Set the viewer’s content (=model)
• Implement getAdapter to return the requested object by the framework

This very brief description doesn’t help one write a functional eclipse plugin but it may help one to keep in mind what to do.