It will be useful also for categorization nodes (Fields, Methods, ...)

Can easily be done by some external code, e.g. Projects API module,
without help from looks.jar. Define some marker class with a name
field and a simple factory, and register a metalook for this class.
Anyway you need to specify the child objects so you will need some
additional machinery for that. IMHO should not be in base Looks API,
though if it used consistently from many modules (not just
projects-api-based) and code sharing is desired it could be added to
some util module in the future.

Jesse, that's clearly a possibility. I discussed this with Hrebejk and he thought that this may use 
useful more generally. He is the owner of looks api so I will let him decide.
As for the child objects you are right -- I using the fact that projects module puts the Project instance 
into a lookup of substitute.

Marking as low priority enhancement. Some kind of support might be 
added later, when we see that it is really necessary. For now it 
sould be enough to create some class representing a group. Which
will hold name of the group and some data from parent. (Holding
data from parent is usaually necessary anyway to be able to produce
child objects etc.) And create a subclass of NamespaceSelector whit
namesFor() method overriden to return the name of the group.

The code which follows demostrates this feature on parsed HAT heap.
The groups will represent Classes and Roots on heap. It is possible
to registrate looks for the groups using XML layer (folder:
Looks/hat/Groups). 

The LookSelector would look like:

public class GroupSelector extends NamespaceSelector {
   
    public static final LookSelector INSTANCE = new GroupSelector();
    
    private static final String PREFIX = "Looks/hat/Group/";
    
    /** Creates a new instance of HeapSelector */
    public GroupSelector() {
        super( PREFIX );
    }
    
    
    public Enumeration namesFor( Object representedObject ) {
        return new SingletonEnumeration(
((Group)representedObject).getName() );
    }
        
    
}


The Group class:

public class Group {
    
    public static final String ROOTS = "ROOTS";
    public static final String CLASSES = "CLASSES";
        
    private Snapshot snapshot;
    private String name;
    
    /** Creates a new instance of Group */
    private Group( String name, Snapshot snapshot ) {
        this.name = name;
        this.snapshot = snapshot;
    }
    
    // Creation methods
    
    public static Group getClasses( Snapshot snapshot ) {
        return new Group( CLASSES, snapshot );
    }
    
    public static Group getRoots( Snapshot snapshot ) {
        return new Group( ROOTS, snapshot );
    }
    
    // Properties
    
    public String getName() {
        return name;
    }
    
    public Snapshot getSnapshot() {
        return snapshot;
    }
    
}

Changing target milestone on all Looks issues to future

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