drools-eclipse/org.drools.eclipse/src/main/java/org/drools/eclipse/editors/rete/ReteViewer.java
protected void initializeGraphicalViewer() {
        ZoomManager zoomManager = rootEditPart.getZoomManager();

        //List<String>
        List<String> zoomLevels = new ArrayList<String>(3);

        zoomLevels.add( ZoomManager.FIT_ALL );
        zoomLevels.add( ZoomManager.FIT_HEIGHT );
        zoomLevels.add( ZoomManager.FIT_WIDTH );

        zoomManager.setZoomLevelContributions( zoomLevels );

        // Zoom mousewheel - Ctrl+Mousewheel for zoom in/out
        getGraphicalViewer().setProperty( MouseWheelHandler.KeyGenerator.getKey( SWT.MOD1 ),
                                          MouseWheelZoomHandler.SINGLETON );

    }
protected void initializeGraphicalViewer() {
        ZoomManager zoomManager = rootEditPart.getZoomManager();

        //List<String>
        List<String> zoomLevels = new ArrayList<String>(3);

        zoomLevels.add( ZoomManager.FIT_ALL );
        zoomLevels.add( ZoomManager.FIT_HEIGHT );
        zoomLevels.add( ZoomManager.FIT_WIDTH );

        zoomManager.setZoomLevelContributions( zoomLevels );

        // Zoom mousewheel - Ctrl+Mousewheel for zoom in/out
        getGraphicalViewer().setProperty( MouseWheelHandler.KeyGenerator.getKey( SWT.MOD1 ),
                                          MouseWheelZoomHandler.SINGLETON );

    }
Loads Rete model and initializes zoom manager.