Boxes represent (sub)processes. A box is a 
rectangular frame, which may contain ports on
its periphery (see help:Editing:Ports).

  How to create a box:
1- select the "edition:box:create" menu function.
2- drag the mouse left button from opposite
   corners in the drawing area.

   Box select/move/kill functions apply to its
attached ports altogether.

   A box has default colors and  minimal sizes,
under X11 resources:
  Atg*boxForeground
  Atg*boxBackground
  Atg*boxminwidth
  Atg*boxminheight

Further box attributes may alter color shades.

   Proper nesting of boxes, and absence of 
overlapping, is NOT checked until explicit
translation/completion is required by the user.

WARNING: not yet implemented:
   Boxes can be reshaped or rescaled from any
corner, using the Edition:box:reshape/rescale
functions. In the first case ports are
projected orthogonally, while in the second case
they keep proportions along the side of the box.
Reshape may abort when ports would project outside 
boundaries.