NSTokenField completion list style

Question

I'm a beginner in OSX development so I hope my question will find a solution here.

I have an NSTokenField in my app and I implemented the tokenField:completionsForSubstring:indexOfToken:indexOfSelectedItem: method.

Everything works fine but the present result look like this :

What I would like is to make it look like this: (similar to the completion in the Mail app)

Which means that I would like the completion list to take all the NSTokenField width. Using the Accessibility Inspector, I can see that the hierarchy corresponding to the first sreenshot is:

AXScrollArea -> AXList -> AXTextField

while the one corresponding to the second screenshot is:

AXScrollArea -> AXTable -> AXRow:AXTableRow -> AXTextField

So I suppose I have to use an NSTableView to display the completion list, but I don't know how to achieve this. Does anybody know how is that possible?

Thanks in advance for your help.

EDIT

At least 2 people suggested that I implement the tokenField:menuForRepresentedObject: method and define the menu width with the appropriate NSMenu property. But this method is used to define a menu for a given token and I already implemented it:

  def tokenField(tokenField, menuForRepresentedObject:representedObject)
    theMenu = NSMenu.alloc.initWithTitle("Email address context menu")
    item_0 = theMenu.insertItemWithTitle('add_to_address_book'.localized, action:'add_to_address_book', keyEquivalent:"", atIndex:0)
    item_0.setTarget(self)
    item_1 = theMenu.insertItemWithTitle('new_message'.localized, action:'new_message', keyEquivalent:"", atIndex:1)
    item_1.setTarget(self)
    theMenu
  end

Which gives me something like this:

Something great but not what I am asking here.