Execute extra functionality when selecting an external context menu in Eclipse plugin

Question

I'm creating an Eclipse plugin where I want to add some pre and post processing tasks that need to be executed automatically when a context menu is executed, this context menu is provided by a third-party plugin so it is not possible for me to modify it, does Eclipse have a mechanism that I can use to intercept the call to a context menu to execute some tasks before and after the actual context menu is executed?

Answer 1

It seems that with EventManager, as mentioned in my comments to the question, it's not working any longer.

I created a New → Project... → Plugin-Project → ... → Template: Menu contribution using 4.x API and adapted HelloWorldHandler:

  @Execute
  public void execute( @Named( IServiceConstants.ACTIVE_SHELL ) final Shell s ) {

    //MessageDialog.openInformation(s, "E4 Information Dialog", "Hello world from a pure Eclipse 4 plug-in");

    final IWorkbenchWindow window = PlatformUI.getWorkbench().getActiveWorkbenchWindow();
    if ( window instanceof WorkbenchWindow ) {

      final MenuManager menu = ( (WorkbenchWindow) window ).getMenuManager();
      final Set<IContributionItem> result = new HashSet<>();
      collectContributions( menu, result );

      result.stream()
          .filter( ci -> ci.getId().equals( "about" ) )
          .forEach( ci -> {
            final IAction a = ( (ActionContributionItem) ci ).getAction();
            System.out.println( a.getDescription() );
            //((Action)a).addListenerObject(null);
            // The method addListenerObject(Object) from the type EventManager is not visible
          } );
    }
  }

  private void collectContributions( final MenuManager menu, final Set<IContributionItem> result ) {

    final IContributionItem[] items = menu.getItems();
    for ( final IContributionItem item2 : items ) {

      IContributionItem item = item2;

      if ( item instanceof SubContributionItem )
        item = ( (SubContributionItem) item ).getInnerItem();

      if ( item instanceof MenuManager )
        collectContributions( (MenuManager) item, result );
      else if ( item instanceof ActionContributionItem && item.isEnabled() )
        result.add( item );
    }
  }

Output

About Eclipse Platform

So, I can get an Action by its ID but contrary to the doc of Action and contrary to the source displayed with F3 in Eclipse (EventManager ← AbstractAction ← Action) it doesn't expose EventManagers methods ("The method addListenerObject(Object) from the type EventManager is not visible"). Probably since the doc of the latter reads:

Warning: Do not use this class! Use ListenerList directly. See bug 486067.

AFAICS if the supplier of the third-party plugin doesn't use this ListenerList and offer a addListener() in his plugin we're out of luck.