Chapters
========

Chapters are a way to store additional metadata on link objects which point 
to targets within the pdf file. This can be used if the pdf file is large 
and/or contains chapters on different topics, thus the different metadata.


    >>> self.loginAsPortalOwner()
    >>> portal_languages = self.portal.portal_languages
    >>> portal_languages.addSupportedLanguage('en')
    >>> portal_languages.addSupportedLanguage('de')
    >>> portal_languages.getSupportedLanguages()
    ['en', 'de']
    >>> default_language = portal_languages.start_neutral and '' or portal_languages.getDefaultLanguage()

We add a new File and make it a publication by subtyping.

    >>> _ = self.folder.invokeFactory('File', 'mypub.pdf')
    >>> mypub = getattr(self.folder, 'mypub.pdf')
    >>> mypub.setTitle('My english File')

    >>> from p4a.subtyper.interfaces import ISubtyper
    >>> from zope.component import getUtility
    >>> subtyper = getUtility(ISubtyper)
    >>> subtyper.change_type(mypub, 'slc.publications.Publication')

Now we add a chapter and call the ObjectModified event to call the handler 
that adds the actual Link objects.

    >>> from slc.publications.utils import _get_storage_folder
    >>> mypub.getField('chapters').getMutator(mypub)(['chapter1'])
    >>> from zope import event
    >>> from zope.app.event import objectevent
    >>> event.notify(objectevent.ObjectModifiedEvent(mypub))
    >>> additionals = _get_storage_folder(mypub)
    >>> additionals.objectIds()
    ['chapter1']
    
If we delete the chapter setting on the publication object, the link in the 
additionals storage is deleted as well.

    >>> mypub.getField('chapters').getMutator(mypub)([])
    >>> event.notify(objectevent.ObjectModifiedEvent(mypub))
    >>> additionals = _get_storage_folder(mypub)
    >>> additionals.objectIds()
    []


