collect which delegate packages were effectively used

[Matteo Moci]

Hello Everyone, 

I'd like to ask if something like this is possible: 

when using different implementations of a template, 

I'd like to keep track of the ones effectively "used" during rendering. 

Let me show the example from the documentation so that my point can be clearer: 

{namespace ...}

{template ...}

  {delcall aaa.bbb.myButton allowemptydefault="false" data="..." /}

{/template}

{deltemplate aaa.bbb.myButton}

…

{/deltemplate}

{delpackage MyExperiment}

{namespace ...}

/** My experiment's implementation. */

{deltemplate aaa.bbb.myButton}

  ...

{/deltemplate}

At render time, when a delcall aaa.bbb.myButton needs to be resolved, Closure Templates looks at all the "active" implementations of the delegate template. 

The active implementations at render time would be [MyExperiment, SomeOtherExperiment]. 

Since the deltemplate aaa.bbb.myButton has delpackage MyExperiment, that package will be effectively used. 

Is there a way to keep track of only the effectively used delpackages? 

I looked into implementing an RendererListener, but I can’t get back the package rendered, due to the fact that RendererListener.templateRendered only takes the templateName as parameter, or maybe I just took the wrong path. 

Thanks! 

Matteo