[pdftex] Optical alignment in hbox

[Paul Pichaureau]

  Hello,

  I would like to use the optical alignment capability of pdftex
inside hbox.

  For example, when I type

   \hbox{Just a roar}

  I would like pdftex automatically add a kern of -(\lpcode of J) at
the left of the \hbox and a kern of (rpcode of r) at the right.

  Do you have any idea how I can force pdftex to do that ?

  I haven't understand yet how pdftex decide to make these optical
adjustments or not: any piece of information will be welcomed.

-- 
 Paul Pichaureau                    http://paulp.nerim.net