@Override
protected void configureGraphicalViewer() {
    ZoomManager zoomManager = ((ScalableFreeformRootEditPart) getGraphicalViewer().getRootEditPart()).getZoomManager();
    IAction zoomIn = new ZoomInAction(zoomManager);
    IAction zoomOut = new ZoomOutAction(zoomManager);
    getActionRegistry().registerAction(zoomIn);
    getActionRegistry().registerAction(zoomOut);
}

@Override
public void contributeToToolBar(IToolBarManager toolBarManager) {
	toolBarManager.add(getAction(GEFActionConstants.ZOOM_IN));
	toolBarManager.add(getAction(GEFActionConstants.ZOOM_OUT));

	String[] zoomStrings = new String[] {
			ZoomManager.FIT_ALL,
			ZoomManager.FIT_HEIGHT,
			ZoomManager.FIT_WIDTH
	};

	toolBarManager.add(new ZoomComboContributionItem(getPage(), zoomStrings));
}