Layer Summary Operation

Plugin.xml extension declaration

<extension
   point="net.refractions.udig.ui.operation">
   <operation
      targetClass="net.refractions.udig.project.ILayer"
      class="net.refractions.udig.project.ui.LayerSummary"
      categoryId="net.refractions.udig.project.ui.informationOperations"
      name="Layer Summary"
      id="net.refractions.udig.project.ui.Operation1"/>
   <category
      name="Information"
      id="net.refractions.udig.project.ui.informationOperations"/>
</extension>

The targetClass indicates which type of objects the operation can operate on. The an instance of the targetClass will be passed to the operation as one of the parameters of the op(...) method.
The class declares the operation class. It must implement the IOp interface.
The categoryId declares which category the operation is part of. This determines where in the operations menu the operation is located.

The category declaration declares a new category called Information. If there are any operations in the category the category will appear in all the Operations menus.

Layer Summary Class

LayerSummary.java

/**
 * Displays a summary of the layer in a dialog.
 * 
 * @author jeichar
 * @since 0.6.0
 */
public class LayerSummary implements IOp {
	/**
	 * @see net.refractions.udig.ui.operations.IOp#op(org.eclipse.swt.widgets.Display,
         * java.lang.Object, org.eclipse.core.runtime.IProgressMonitor)
	 */
	public void op(final Display display, Object target, IProgressMonitor monitor) throws Exception {
           final Layer layer=(Layer) target;
	   monitor.beginTask("Layer Summary", 1);
           Envelope bounds=layer.getBounds(monitor, layer.getMap().getViewportModel().getCRS());
           final StringBuffer buffer=new StringBuffer();
           buffer.append("Name: "+layer.getName()+"\n");
           buffer.append("ID: "+layer.getID()+"\n");
           buffer.append("z-order: "+layer.getZorder()+"\n");
           buffer.append("Data CRS: "+layer.getCRS(monitor).getName()+"\n");
           buffer.append("Bounds: ("+bounds.getMinX()+","+bounds.getMinY()+")\n");
           buffer.append("            ("+bounds.getMaxX()+","+bounds.getMaxY()+"\n");
           buffer.append("Selection Filter: "+layer.getFilter()+"\n");
           display.asyncExec(new Runnable() {
			public void run() {
		        MessageDialog.openInformation(display.getActiveShell(), "Summary of "+
                               layer.getName(), buffer.toString());
			}
		});
	   monitor.internalWorked(1);
	   monitor.done();
        }

}

The parameter display is a display object the operation can use in order to interact with the User interface. The target parameter is guaranteed to be of the same type declared in the targetClass attribute of the xml extension declaration. The monitor parameter allows the operation to provide feedback to the UI on how much of the operation has been completed.