Can we expose the name of the chosen theme file as a variable?

[djowett]

(moved from plone/plone.app.theming#104)

I'd like to be able to do this

 <!-- Multiple conditions for choosing a theme file --> 
<theme href="leaf.html"
       css:if-content="body.template-pontprennauview"/>

<!-- Manage portlets for covers  -->
<theme href="leaf.html"
       css:if-content="body.portaltype-collective-cover-content.template-manage-portlets"/>

<!-- A 'normal' page or content item -->
<theme href="leaf.html"
       css:if-content="#visual-portal-wrapper"/>

....
<!-- Cover all occasions we use a particular theme file without a complex condition -->
<rules if="$theme == 'leaf.html'">
....
</rules>

Correct me if I'm wrong, but I don't think that's currently possible/easy?