How to add Zoom facility to the GEF editor?

Often on the GEF newsgroup there can be found questions concerning zooming in the GEF editor. I tried to investigate this subject and found out that adding basic zooming operations isn't to complicated. All required code I found in the Logic GEF example project: org.eclipse.gef.examples.logic project, which can be checkout from the CVS (if you don't know how to access Eclipse CVS check this page: WIKI CVS HowTo).
To demonstrate the solution I will use another GEF example, but this time it will be Shape Editor project: org.eclipse.gef.examples.shapes, which also can be checkout form the CVS. Shape Editor is very simple GEF editor, which allows you only to add two figures and connect them with two connection types. We will want to add the zooming facility to this poor functionality.

Zoom actions can be added in two ways:

• by the toolbar
• by the menu

To add zooming action to the toolbar we need to:

• In the class
  org.eclipse.gef.examples.shapes.ShapesEditorActionBarContributor you need to overwrite method
  EditorActionBarContributor#contributeToToolBar
  and add this code:
  
  String[] zoomStrings = new String[] {
  ZoomManager.FIT_ALL, ZoomManager.FIT_HEIGHT,
  ZoomManager.FIT_WIDTH
  };
  toolBarManager.add(newZoomComboContributionItem(getPage(), zoomStrings));
  
  

• in the class org.eclipse.gef.examples.shapes.ShapesEditor
  in the method configureGraphicalViewer
  you need to add such code:
  List zoomLevels = new ArrayList(3);
  zoomLevels.add(ZoomManager.FIT_ALL);
  zoomLevels.add(ZoomManager.FIT_WIDTH);
  zoomLevels.add(ZoomManager.FIT_HEIGHT);
  root.getZoomManager().setZoomLevelContributions(zoomLevels);

Where root is an instance of ScalableFreeformRootEditPart which you should pass as a parameter to: viewer.setRootEditPart(root); These string values - ZoomManager.FIT_ALL, ZoomManager.FIT_WIDTH and ZoomManager.FIT_HEIGHT are the additional zoom levels added to the zoom combobox.

• in the class org.eclipse.gef.examples.shapes.ShapesEditor
  in the method getAdapter
  you need to add such code:
  if (type == ZoomManager.class) {
  return getGraphicalViewer().getProperty(ZoomManager.class.toString());
  }

And that's all! You should see similar effect to this one in the picture below:

Now let's see what are we suppose to do to add the zooming to the main Eclipse menu

• in the class org.eclipse.gef.examples.shapes.ShapesEditor in the method configureGraphicalViewer you need to add such code:

IAction zoomIn = new ZoomInAction(root.getZoomManager());
IAction zoomOut = new ZoomOutAction(root.getZoomManager())
getActionRegistry().registerAction(zoomIn);
getActionRegistry().registerAction(zoomOut);

and additionaly if you want to have the keyboard shortcuts you have to add:
getSite().getKeyBindingService().registerAction(zoomIn);
getSite().getKeyBindingService().registerAction(zoomOut);

• in the class org.eclipse.gef.examples.shapes.ShapesEditorActionBarContributoryou need to overwrite method
  EditorActionBarContributor#contributeToMenu(IMenuManager)and add there:
  super.contributeToMenu(menubar);
  MenuManager viewMenu = newMenuManager("ZOOM");
  viewMenu.add(getAction(GEFActionConstants.ZOOM_IN));
  viewMenu.add(getAction(GEFActionConstants.ZOOM_OUT));
  menubar.insertAfter(IWorkbenchActionConstants.M_EDIT,viewMenu); //where the menu should placed on the menu bar

The effect you can see below: