/*! \page fmt_overview Formatter

    FL_DocLayout is a formatted representation of a specific PD_Document, 
    formatted for a specific GR_Graphics context.  

    A %FL_DocLayout encapsulates two related hierarchies of objects.  

    The <em>logical</em> (or <em>content</em>) hierarchy corresponds
    to the logical structure of the document.

        - each FL_DocLayout contains a list of fl_SectionLayout objects
        - each fl_SectionLayout are composed of fl_BlockLayout objects

    Where each fl_BlockLayout corresponds to a logical element in
    the PD_Document (i.e., usually a paragraph of text).

    The <em>physical</em> (or <em>layout</em>) hierarchy, by contrast,
    encapsulates the subdivision of physical space into objects of
    successively finer granularity.

        - each FL_DocLayout contains a list of fp_Page objects, each
          of which was constructed during the process of formatting
          the document
        - each fp_Page is a list of fp_Columns (fp_Column)
        - each fp_Column is a list of fp_Lines (fp_Line)
        - each fp_Line is a list of fp_Runs (fp_Run)

    Where each fp_Run contains some fragment of content from the original 
    document, usually text.  

<h3>Other subjects</h3>

- \ref squiggle_overview used by the spell checker.

*/
