Sure thing. That was part of my original intention.

Cool :) Thanks

When I try...
self whenBuiltDo: [ self halt. self window whenClosedDo: [ self halt. self repository unsubscribe: self ] ].
none of the halts occur.

However I got what I needed with the following�

did you try to register in the initialize method ?

Because if you register once the application is already open, it may not work :)

----------
   ComposableModel>>topWindowHolder
         ^ owner
              ifNil: [ window ]
                ifNotNil: [ :o | o topWindowHolder ].
----------
ComposableModel>>whenWindowClosed: aBlock
      self topWindowHolder value
        ifNotNil: [ :w | w whenClosedDo: aBlock ]
          ifNil: [ self topWindowHolder whenChangedDo: [ :w | w whenClosedDo: aBlock ] ].
----------
    PhLTitledTreeModel>>repository: aRepository
       self assert: self repository isNil description: 'Changing the repository is not allowed because we would have to change the context as well'.
        repositoryHolder value: aRepository.
        self repository whenChangedSend: #refresh to: self.
        self whenWindowClosed: [ self repository unsubscribe: self.   self inform: 'Works for composed sub-items'. ] .
      self refresh
----------
    PharoLauncher>>initialize
        super initialize.
        self whenWindowClosed: [ self inform: 'Works for top level owner' ].
----------
And optionally you could now have...
    ComposableModel>>window
        ^ self topWindowHolder value
��

topWindowHolder sounds a bit hackish :)

I think this can be achieved with the whenBuiltDo:, I should investigate :)

If those ComposableModel additions are okay, I'll submit a slice on Case 12677 (renamed to "ComposableModel subcomponents need to act on window close")
https://pharo.fogbugz.com/f/cases/12677/

You can also submitted here: https://github.com/SpecForPharo/spec if you want :)