Using org.eclipse.ui.menu 3.3 API for popup menu

I am not sure new qualifier still apply for an API available since Eclipse 3.3, but here are some questions I have asked myself and for which I would like to share some answers.

• Where can I find a good introduction to the new API ?
  

There is a great IBM article ideal to discover the API.

• Where can I find id for group ?

Have a look at the following interfaces :

org.eclipse.ui.IWorkbenchActionConstants
org.eclipse.ui.navigator.ICommonMenuConstant

• Where can I find available variables ?

On the Eclipse wiki.

• Where can I find an eclipse plug-in example ?

In one ATL plug-in for instance. Here is an example where the popup menu item is displayed only when the active perspective is the right one, and the selected files extension is ecore.

• How can I get the selection for popup menu ?

Be careful the selection variable is not the same for classic menu and popup menu.
You have to use activeSelectionMenu.

• How can I do to not display the menu if the selection is empty ?

You have to use count element.

<visiblewhen checkenabled="false">
   <with variable="activeMenuSelection">
       <iterate operator="and">
         <count value="+">
        </count>
       </iterate>
   </with>
<visiblewhen>

• How could I call a test in Java ?

First you have to create a property tester :

<extension point="org.eclipse.core.expressions.propertyTesters">
 <propertytester id="com.mycompany.project.tester.MyTester"
  type="org.eclipse.gmf.runtime.diagram.ui.editparts.IGraphicalEditPart"
  namespace="com.mycompany.project.namespace" properties="isLikeIWant"
  class="com.mycompany.project.namespace.MyTesterClass">
 </propertytester>
</extension>

Then you can use it with test element :

  <visiblewhen checkenabled="false">
     <with variable="activeMenuSelection">
        <iterate operator="and">
           <instanceof value="org.eclipse.gmf.runtime.diagram.ui.editparts.IGraphicalEditPart"></instanceof>
           <test property="com.mycompany.project.namespace.isLikeIWant"></test>
           </iterate>
    </with>
  </visiblewhen>