create horisontal and vertical flowing layouts/tiling
parboxes. For a phbox, the box will arrange its components into a
set of rows of the width allocated to it. Within each row, the
components are resized according to the same rules as for hbox and
vbox. The Geometry argument specify the spacing between the rows
(for phbox) and columns (for pvbox) and maybe the desired length
for the rows/columns (see See section Geometric requirements for definition of Geometry
geo = Space ghint => ghint specifies the inter-row spacing
geo = Geo ghintx ghinty => ghintx the geometric requirements for a row,
ghinty the inter-row spacing.
geo = Space ghint => ghint is the inter-column spacing
geo = Geo ghintx ghinty => ghintx is the geometric hint for the columns,
ghinty the inter-column spacing.