This static computation step performs manual linebreaks on all paragraphs.
This transforms the pool-collection into the lines-collection.
For now, we follow a very simple path: A paragraph cannot be validated, if it
is not yet closed.
This final processing step revalidates the text-layouting and the vertical alignment of block-level elements.
At this point, the layout is almost finished, but non-dynamic text elements may contain more content on the
last line than actually needed.